> On Mon, Nov 30, 2020 at 02:26:19PM +0100, Dmitry Dolgov wrote:
> > On Mon, Nov 30, 2020 at 04:12:29PM +0300, Alexander Korotkov wrote:
> >
> > > > My first question is whether we're
> > > > able to handle different subscript types differently.  For instance,
> > > > one day we could handle jsonpath subscripts for jsonb.  And for sure,
> > > > jsonpath subscripts are expected to be handled differently from text
> > > > subscripts.  I see we can distinguish types during in prepare and
> > > > validate functions.  But it seems there is no type information in
> > > > fetch and assign functions.  Should we add something like this to the
> > > > SubscriptingRefState for future usage?
> > > >
> > > > Datum uppertypeoid[MAX_SUBSCRIPT_DEPTH];
> > > > Datum lowertypeoid[MAX_SUBSCRIPT_DEPTH];
> > >
> > > Yes, makes sense. My original idea was that it could be done within the
> > > jsonpath support patch itself, but at the same time providing these
> > > fields into SubscriptingRefState will help other potential extensions.
> > >
> > > Having said that, maybe it would be even better to introduce a field
> > > with an opaque structure for both SubscriptingRefState and
> > > SubscriptingRef, where every implementation of custom subscripting can
> > > store any necessary information? In case of jsonpath it could keep type
> > > information acquired in prepare function, which would be then passed via
> > > SubscriptingRefState down to the fetch/assign.
> >
> > The idea of an opaque field in SubscriptingRef structure is more
> > attractive to me.  Could you please implement it?
>
> Sure, doesn't seem to be that much work.

The attached implementation should be enough I guess, as fetch/assign
are executed in a child memory context of one where prepare does the
stuff.
>From 6f7d9589cc827dfb3b1d82a3e0e629b482e4c77a Mon Sep 17 00:00:00 2001
From: erthalion <9erthali...@gmail.com>
Date: Thu, 31 Jan 2019 22:37:19 +0100
Subject: [PATCH v35 1/5] Base implementation of subscripting mechanism

Introduce all the required machinery for generalizing subscripting
operation for a different data types:

* subscripting handler procedure, to set up a relation between data type
and corresponding subscripting logic.

* subscripting routines, that help generalize a subscripting logic,
since it involves few stages, namely preparation (e.g. to figure out
required types), validation (to check the input and return meaningful
error message), fetch (executed when we extract a value using
subscripting), assign (executed when we update a data type with a new
value using subscripting). Without this it would be neccessary to
introduce more new fields to pg_type, which would be too invasive.

All ArrayRef related logic was removed and landed as a separate
subscripting implementation in the following patch from this series. The
rest of the code was rearranged, to e.g. store a type of assigned value
for an assign operation.

Reviewed-by: Tom Lane, Arthur Zakirov
---
 .../pg_stat_statements/pg_stat_statements.c   |   1 +
 src/backend/catalog/heap.c                    |   6 +-
 src/backend/catalog/pg_type.c                 |   7 +-
 src/backend/commands/typecmds.c               |  77 +++++++++-
 src/backend/executor/execExpr.c               |  26 +---
 src/backend/executor/execExprInterp.c         | 124 +++------------
 src/backend/nodes/copyfuncs.c                 |   2 +
 src/backend/nodes/equalfuncs.c                |   2 +
 src/backend/nodes/outfuncs.c                  |   2 +
 src/backend/nodes/readfuncs.c                 |   2 +
 src/backend/parser/parse_expr.c               |  54 ++++---
 src/backend/parser/parse_node.c               | 141 ++++--------------
 src/backend/parser/parse_target.c             |  88 +++++------
 src/backend/utils/adt/ruleutils.c             |  21 +--
 src/backend/utils/cache/lsyscache.c           |  23 +++
 src/include/c.h                               |   2 +
 src/include/catalog/pg_type.h                 |   9 +-
 src/include/executor/execExpr.h               |  15 +-
 src/include/nodes/primnodes.h                 |   8 +
 src/include/nodes/subscripting.h              |  42 ++++++
 src/include/parser/parse_node.h               |   6 +-
 src/include/utils/lsyscache.h                 |   1 +
 22 files changed, 333 insertions(+), 326 deletions(-)
 create mode 100644 src/include/nodes/subscripting.h

diff --git a/contrib/pg_stat_statements/pg_stat_statements.c b/contrib/pg_stat_statements/pg_stat_statements.c
index 1eac9edaee..31ba120fb2 100644
--- a/contrib/pg_stat_statements/pg_stat_statements.c
+++ b/contrib/pg_stat_statements/pg_stat_statements.c
@@ -2800,6 +2800,7 @@ JumbleExpr(pgssJumbleState *jstate, Node *node)
 				JumbleExpr(jstate, (Node *) sbsref->reflowerindexpr);
 				JumbleExpr(jstate, (Node *) sbsref->refexpr);
 				JumbleExpr(jstate, (Node *) sbsref->refassgnexpr);
+				APP_JUMB(sbsref->refnestedfunc);
 			}
 			break;
 		case T_FuncExpr:
diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index 67144aa3c9..4d552589ae 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -1091,7 +1091,8 @@ AddNewRelationType(const char *typeName,
 				   -1,			/* typmod */
 				   0,			/* array dimensions for typBaseType */
 				   false,		/* Type NOT NULL */
-				   InvalidOid); /* rowtypes never have a collation */
+				   InvalidOid,  /* rowtypes never have a collation */
+				   InvalidOid);	/* typsubshandler - none */
 }
 
 /* --------------------------------
@@ -1370,7 +1371,8 @@ heap_create_with_catalog(const char *relname,
 				   -1,			/* typmod */
 				   0,			/* array dimensions for typBaseType */
 				   false,		/* Type NOT NULL */
-				   InvalidOid); /* rowtypes never have a collation */
+				   InvalidOid,  /* rowtypes never have a collation */
+				   0);	/* array implementation */
 
 		pfree(relarrayname);
 	}
diff --git a/src/backend/catalog/pg_type.c b/src/backend/catalog/pg_type.c
index 0b04dff773..7744bca30a 100644
--- a/src/backend/catalog/pg_type.c
+++ b/src/backend/catalog/pg_type.c
@@ -118,6 +118,7 @@ TypeShellMake(const char *typeName, Oid typeNamespace, Oid ownerId)
 	values[Anum_pg_type_typtypmod - 1] = Int32GetDatum(-1);
 	values[Anum_pg_type_typndims - 1] = Int32GetDatum(0);
 	values[Anum_pg_type_typcollation - 1] = ObjectIdGetDatum(InvalidOid);
+	values[Anum_pg_type_typsubshandler - 1] = ObjectIdGetDatum(InvalidOid);
 	nulls[Anum_pg_type_typdefaultbin - 1] = true;
 	nulls[Anum_pg_type_typdefault - 1] = true;
 	nulls[Anum_pg_type_typacl - 1] = true;
@@ -158,10 +159,10 @@ TypeShellMake(const char *typeName, Oid typeNamespace, Oid ownerId)
 		GenerateTypeDependencies(tup,
 								 pg_type_desc,
 								 NULL,
-								 NULL,
 								 0,
 								 false,
 								 false,
+								 InvalidOid,
 								 false);
 
 	/* Post creation hook for new shell type */
@@ -219,7 +220,8 @@ TypeCreate(Oid newTypeOid,
 		   int32 typeMod,
 		   int32 typNDims,		/* Array dimensions for baseType */
 		   bool typeNotNull,
-		   Oid typeCollation)
+		   Oid typeCollation,
+		   Oid subscriptingHandlerProcedure)
 {
 	Relation	pg_type_desc;
 	Oid			typeObjectId;
@@ -372,6 +374,7 @@ TypeCreate(Oid newTypeOid,
 	values[Anum_pg_type_typtypmod - 1] = Int32GetDatum(typeMod);
 	values[Anum_pg_type_typndims - 1] = Int32GetDatum(typNDims);
 	values[Anum_pg_type_typcollation - 1] = ObjectIdGetDatum(typeCollation);
+	values[Anum_pg_type_typsubshandler - 1] = ObjectIdGetDatum(subscriptingHandlerProcedure);
 
 	/*
 	 * initialize the default binary value for this type.  Check for nulls of
diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c
index 483bb65ddc..33d4fb401d 100644
--- a/src/backend/commands/typecmds.c
+++ b/src/backend/commands/typecmds.c
@@ -115,6 +115,7 @@ static Oid	findTypeSendFunction(List *procname, Oid typeOid);
 static Oid	findTypeTypmodinFunction(List *procname);
 static Oid	findTypeTypmodoutFunction(List *procname);
 static Oid	findTypeAnalyzeFunction(List *procname, Oid typeOid);
+static Oid	findTypeSubscriptingFunction(List *procname, Oid typeOid, bool parseFunc);
 static Oid	findRangeSubOpclass(List *opcname, Oid subtype);
 static Oid	findRangeCanonicalFunction(List *procname, Oid typeOid);
 static Oid	findRangeSubtypeDiffFunction(List *procname, Oid subtype);
@@ -149,6 +150,7 @@ DefineType(ParseState *pstate, List *names, List *parameters)
 	List	   *typmodinName = NIL;
 	List	   *typmodoutName = NIL;
 	List	   *analyzeName = NIL;
+	List	   *subscriptingParseName = NIL;
 	char		category = TYPCATEGORY_USER;
 	bool		preferred = false;
 	char		delimiter = DEFAULT_TYPDELIM;
@@ -167,6 +169,7 @@ DefineType(ParseState *pstate, List *names, List *parameters)
 	DefElem    *typmodinNameEl = NULL;
 	DefElem    *typmodoutNameEl = NULL;
 	DefElem    *analyzeNameEl = NULL;
+	DefElem    *subscriptingParseNameEl = NULL;
 	DefElem    *categoryEl = NULL;
 	DefElem    *preferredEl = NULL;
 	DefElem    *delimiterEl = NULL;
@@ -188,6 +191,7 @@ DefineType(ParseState *pstate, List *names, List *parameters)
 	Oid			typoid;
 	ListCell   *pl;
 	ObjectAddress address;
+	Oid			subscriptingParseOid = InvalidOid;
 
 	/*
 	 * As of Postgres 8.4, we require superuser privilege to create a base
@@ -288,6 +292,8 @@ DefineType(ParseState *pstate, List *names, List *parameters)
 		else if (strcmp(defel->defname, "analyze") == 0 ||
 				 strcmp(defel->defname, "analyse") == 0)
 			defelp = &analyzeNameEl;
+		else if (strcmp(defel->defname, "subscripting_handler") == 0)
+			defelp = &subscriptingParseNameEl;
 		else if (strcmp(defel->defname, "category") == 0)
 			defelp = &categoryEl;
 		else if (strcmp(defel->defname, "preferred") == 0)
@@ -358,6 +364,8 @@ DefineType(ParseState *pstate, List *names, List *parameters)
 		typmodoutName = defGetQualifiedName(typmodoutNameEl);
 	if (analyzeNameEl)
 		analyzeName = defGetQualifiedName(analyzeNameEl);
+	if (subscriptingParseNameEl)
+		subscriptingParseName = defGetQualifiedName(subscriptingParseNameEl);
 	if (categoryEl)
 	{
 		char	   *p = defGetString(categoryEl);
@@ -482,6 +490,10 @@ DefineType(ParseState *pstate, List *names, List *parameters)
 	if (analyzeName)
 		analyzeOid = findTypeAnalyzeFunction(analyzeName, typoid);
 
+	if (subscriptingParseName)
+		subscriptingParseOid = findTypeSubscriptingFunction(subscriptingParseName,
+															typoid, true);
+
 	/*
 	 * Check permissions on functions.  We choose to require the creator/owner
 	 * of a type to also own the underlying functions.  Since creating a type
@@ -563,7 +575,8 @@ DefineType(ParseState *pstate, List *names, List *parameters)
 				   -1,			/* typMod (Domains only) */
 				   0,			/* Array Dimensions of typbasetype */
 				   false,		/* Type NOT NULL */
-				   collation);	/* type's collation */
+				   collation,	/* type's collation */
+				   subscriptingParseOid);	/* subscripting procedure */
 	Assert(typoid == address.objectId);
 
 	/*
@@ -604,7 +617,8 @@ DefineType(ParseState *pstate, List *names, List *parameters)
 			   -1,				/* typMod (Domains only) */
 			   0,				/* Array dimensions of typbasetype */
 			   false,			/* Type NOT NULL */
-			   collation);		/* type's collation */
+			   collation,		/* type's collation */
+			   0);
 
 	pfree(array_type);
 
@@ -667,6 +681,7 @@ DefineDomain(CreateDomainStmt *stmt)
 	Oid			receiveProcedure;
 	Oid			sendProcedure;
 	Oid			analyzeProcedure;
+	Oid			subscriptingHandlerProcedure;
 	bool		byValue;
 	char		category;
 	char		delimiter;
@@ -800,6 +815,9 @@ DefineDomain(CreateDomainStmt *stmt)
 	/* Analysis function */
 	analyzeProcedure = baseType->typanalyze;
 
+	/* Subscripting functions */
+	subscriptingHandlerProcedure = baseType->typsubshandler;
+
 	/* Inherited default value */
 	datum = SysCacheGetAttr(TYPEOID, typeTup,
 							Anum_pg_type_typdefault, &isnull);
@@ -1005,7 +1023,8 @@ DefineDomain(CreateDomainStmt *stmt)
 				   basetypeMod, /* typeMod value */
 				   typNDims,	/* Array dimensions for base type */
 				   typNotNull,	/* Type NOT NULL */
-				   domaincoll); /* type's collation */
+				   domaincoll,  /* type's collation */
+				   subscriptingHandlerProcedure);	/* subscripting procedure */
 
 	/*
 	 * Create the array type that goes with it.
@@ -1045,7 +1064,8 @@ DefineDomain(CreateDomainStmt *stmt)
 			   -1,				/* typMod (Domains only) */
 			   0,				/* Array dimensions of typbasetype */
 			   false,			/* Type NOT NULL */
-			   domaincoll);		/* type's collation */
+			   domaincoll,		/* type's collation */
+			   0); /* array subscripting implementation */
 
 	pfree(domainArrayName);
 
@@ -1160,7 +1180,8 @@ DefineEnum(CreateEnumStmt *stmt)
 				   -1,			/* typMod (Domains only) */
 				   0,			/* Array dimensions of typbasetype */
 				   false,		/* Type NOT NULL */
-				   InvalidOid); /* type's collation */
+				   InvalidOid,  /* type's collation */
+				   InvalidOid);	/* typsubshandler - none */
 
 	/* Enter the enum's values into pg_enum */
 	EnumValuesCreate(enumTypeAddr.objectId, stmt->vals);
@@ -1200,7 +1221,8 @@ DefineEnum(CreateEnumStmt *stmt)
 			   -1,				/* typMod (Domains only) */
 			   0,				/* Array dimensions of typbasetype */
 			   false,			/* Type NOT NULL */
-			   InvalidOid);		/* type's collation */
+			   InvalidOid,		/* type's collation */
+			   0);	/* array subscripting implementation */
 
 	pfree(enumArrayName);
 
@@ -1488,7 +1510,8 @@ DefineRange(CreateRangeStmt *stmt)
 				   -1,			/* typMod (Domains only) */
 				   0,			/* Array dimensions of typbasetype */
 				   false,		/* Type NOT NULL */
-				   InvalidOid); /* type's collation (ranges never have one) */
+				   InvalidOid,  /* type's collation (ranges never have one) */
+				   InvalidOid);	/* typsubshandler - none */
 	Assert(typoid == InvalidOid || typoid == address.objectId);
 	typoid = address.objectId;
 
@@ -1531,7 +1554,8 @@ DefineRange(CreateRangeStmt *stmt)
 			   -1,				/* typMod (Domains only) */
 			   0,				/* Array dimensions of typbasetype */
 			   false,			/* Type NOT NULL */
-			   InvalidOid);		/* typcollation */
+			   InvalidOid,		/* typcollation */
+			   0);	/* array subscripting implementation */
 
 	pfree(rangeArrayName);
 
@@ -1904,6 +1928,43 @@ findTypeAnalyzeFunction(List *procname, Oid typeOid)
 	return procOid;
 }
 
+static Oid
+findTypeSubscriptingFunction(List *procname, Oid typeOid, bool parseFunc)
+{
+	Oid			argList[2];
+	Oid			procOid;
+	int			nargs;
+
+	if (parseFunc)
+	{
+		/*
+		 * Subscripting parse functions always take two INTERNAL arguments and
+		 * return INTERNAL.
+		 */
+		argList[0] = INTERNALOID;
+		nargs = 1;
+	}
+	else
+	{
+		/*
+		 * Subscripting fetch/assign functions always take one typeOid
+		 * argument, one INTERNAL argument and return typeOid.
+		 */
+		argList[0] = typeOid;
+		argList[1] = INTERNALOID;
+		nargs = 2;
+	}
+
+	procOid = LookupFuncName(procname, nargs, argList, true);
+	if (!OidIsValid(procOid))
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_FUNCTION),
+				 errmsg("function %s does not exist",
+						func_signature_string(procname, nargs, NIL, argList))));
+
+	return procOid;
+}
+
 /*
  * Find suitable support functions and opclasses for a range type.
  */
diff --git a/src/backend/executor/execExpr.c b/src/backend/executor/execExpr.c
index 236413f62a..a18fe5f9d0 100644
--- a/src/backend/executor/execExpr.c
+++ b/src/backend/executor/execExpr.c
@@ -2545,18 +2545,17 @@ ExecInitSubscriptingRef(ExprEvalStep *scratch, SubscriptingRef *sbsref,
 {
 	bool		isAssignment = (sbsref->refassgnexpr != NULL);
 	SubscriptingRefState *sbsrefstate = palloc0(sizeof(SubscriptingRefState));
-	List	   *adjust_jumps = NIL;
-	ListCell   *lc;
-	int			i;
+	List				 *adjust_jumps = NIL;
+	ListCell   			 *lc;
+	int		   			  i;
+	RegProcedure		  typsubshandler = get_typsubsprocs(sbsref->refcontainertype);
 
 	/* Fill constant fields of SubscriptingRefState */
 	sbsrefstate->isassignment = isAssignment;
 	sbsrefstate->refelemtype = sbsref->refelemtype;
 	sbsrefstate->refattrlength = get_typlen(sbsref->refcontainertype);
-	get_typlenbyvalalign(sbsref->refelemtype,
-						 &sbsrefstate->refelemlength,
-						 &sbsrefstate->refelembyval,
-						 &sbsrefstate->refelemalign);
+	sbsrefstate->sbsroutines = (SubscriptRoutines *) OidFunctionCall0(typsubshandler);
+	sbsrefstate->refopaque = sbsref->refopaque;
 
 	/*
 	 * Evaluate array input.  It's safe to do so into resv/resnull, because we
@@ -2580,19 +2579,6 @@ ExecInitSubscriptingRef(ExprEvalStep *scratch, SubscriptingRef *sbsref,
 								   state->steps_len - 1);
 	}
 
-	/* Verify subscript list lengths are within limit */
-	if (list_length(sbsref->refupperindexpr) > MAXDIM)
-		ereport(ERROR,
-				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-				 errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
-						list_length(sbsref->refupperindexpr), MAXDIM)));
-
-	if (list_length(sbsref->reflowerindexpr) > MAXDIM)
-		ereport(ERROR,
-				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-				 errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
-						list_length(sbsref->reflowerindexpr), MAXDIM)));
-
 	/* Evaluate upper subscripts */
 	i = 0;
 	foreach(lc, sbsref->refupperindexpr)
diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index b812bbacee..838bb4d005 100644
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -3146,8 +3146,8 @@ bool
 ExecEvalSubscriptingRef(ExprState *state, ExprEvalStep *op)
 {
 	SubscriptingRefState *sbsrefstate = op->d.sbsref_subscript.state;
-	int		   *indexes;
-	int			off;
+	Datum				 *indexes;
+	int					 off;
 
 	/* If any index expr yields NULL, result is NULL or error */
 	if (sbsrefstate->subscriptnull)
@@ -3167,7 +3167,7 @@ ExecEvalSubscriptingRef(ExprState *state, ExprEvalStep *op)
 		indexes = sbsrefstate->lowerindex;
 	off = op->d.sbsref_subscript.off;
 
-	indexes[off] = DatumGetInt32(sbsrefstate->subscriptvalue);
+	indexes[off] = sbsrefstate->subscriptvalue;
 
 	return true;
 }
@@ -3181,36 +3181,14 @@ void
 ExecEvalSubscriptingRefFetch(ExprState *state, ExprEvalStep *op)
 {
 	SubscriptingRefState *sbsrefstate = op->d.sbsref.state;
+	SubscriptRoutines	 *sbsroutines = sbsrefstate->sbsroutines;
 
 	/* Should not get here if source container (or any subscript) is null */
 	Assert(!(*op->resnull));
 
-	if (sbsrefstate->numlower == 0)
-	{
-		/* Scalar case */
-		*op->resvalue = array_get_element(*op->resvalue,
-										  sbsrefstate->numupper,
-										  sbsrefstate->upperindex,
-										  sbsrefstate->refattrlength,
-										  sbsrefstate->refelemlength,
-										  sbsrefstate->refelembyval,
-										  sbsrefstate->refelemalign,
-										  op->resnull);
-	}
-	else
-	{
-		/* Slice case */
-		*op->resvalue = array_get_slice(*op->resvalue,
-										sbsrefstate->numupper,
-										sbsrefstate->upperindex,
-										sbsrefstate->lowerindex,
-										sbsrefstate->upperprovided,
-										sbsrefstate->lowerprovided,
-										sbsrefstate->refattrlength,
-										sbsrefstate->refelemlength,
-										sbsrefstate->refelembyval,
-										sbsrefstate->refelemalign);
-	}
+
+	*op->resvalue = sbsroutines->fetch(*op->resvalue, sbsrefstate);
+	*op->resnull = sbsrefstate->resnull;
 }
 
 /*
@@ -3223,40 +3201,20 @@ void
 ExecEvalSubscriptingRefOld(ExprState *state, ExprEvalStep *op)
 {
 	SubscriptingRefState *sbsrefstate = op->d.sbsref.state;
+	SubscriptRoutines	 *sbsroutines = sbsrefstate->sbsroutines;
 
 	if (*op->resnull)
 	{
-		/* whole array is null, so any element or slice is too */
+		/* whole container is null, so any element or slice is too */
 		sbsrefstate->prevvalue = (Datum) 0;
 		sbsrefstate->prevnull = true;
 	}
-	else if (sbsrefstate->numlower == 0)
-	{
-		/* Scalar case */
-		sbsrefstate->prevvalue = array_get_element(*op->resvalue,
-												   sbsrefstate->numupper,
-												   sbsrefstate->upperindex,
-												   sbsrefstate->refattrlength,
-												   sbsrefstate->refelemlength,
-												   sbsrefstate->refelembyval,
-												   sbsrefstate->refelemalign,
-												   &sbsrefstate->prevnull);
-	}
 	else
 	{
-		/* Slice case */
-		/* this is currently unreachable */
-		sbsrefstate->prevvalue = array_get_slice(*op->resvalue,
-												 sbsrefstate->numupper,
-												 sbsrefstate->upperindex,
-												 sbsrefstate->lowerindex,
-												 sbsrefstate->upperprovided,
-												 sbsrefstate->lowerprovided,
-												 sbsrefstate->refattrlength,
-												 sbsrefstate->refelemlength,
-												 sbsrefstate->refelembyval,
-												 sbsrefstate->refelemalign);
-		sbsrefstate->prevnull = false;
+		sbsrefstate->prevvalue = sbsroutines->fetch(*op->resvalue, sbsrefstate);
+
+		if (sbsrefstate->numlower != 0)
+			sbsrefstate->prevnull = false;
 	}
 }
 
@@ -3270,59 +3228,11 @@ void
 ExecEvalSubscriptingRefAssign(ExprState *state, ExprEvalStep *op)
 {
 	SubscriptingRefState *sbsrefstate = op->d.sbsref_subscript.state;
+	SubscriptRoutines	 *sbsroutines = sbsrefstate->sbsroutines;
 
-	/*
-	 * For an assignment to a fixed-length container type, both the original
-	 * container and the value to be assigned into it must be non-NULL, else
-	 * we punt and return the original container.
-	 */
-	if (sbsrefstate->refattrlength > 0)
-	{
-		if (*op->resnull || sbsrefstate->replacenull)
-			return;
-	}
-
-	/*
-	 * For assignment to varlena arrays, we handle a NULL original array by
-	 * substituting an empty (zero-dimensional) array; insertion of the new
-	 * element will result in a singleton array value.  It does not matter
-	 * whether the new element is NULL.
-	 */
-	if (*op->resnull)
-	{
-		*op->resvalue = PointerGetDatum(construct_empty_array(sbsrefstate->refelemtype));
-		*op->resnull = false;
-	}
-
-	if (sbsrefstate->numlower == 0)
-	{
-		/* Scalar case */
-		*op->resvalue = array_set_element(*op->resvalue,
-										  sbsrefstate->numupper,
-										  sbsrefstate->upperindex,
-										  sbsrefstate->replacevalue,
-										  sbsrefstate->replacenull,
-										  sbsrefstate->refattrlength,
-										  sbsrefstate->refelemlength,
-										  sbsrefstate->refelembyval,
-										  sbsrefstate->refelemalign);
-	}
-	else
-	{
-		/* Slice case */
-		*op->resvalue = array_set_slice(*op->resvalue,
-										sbsrefstate->numupper,
-										sbsrefstate->upperindex,
-										sbsrefstate->lowerindex,
-										sbsrefstate->upperprovided,
-										sbsrefstate->lowerprovided,
-										sbsrefstate->replacevalue,
-										sbsrefstate->replacenull,
-										sbsrefstate->refattrlength,
-										sbsrefstate->refelemlength,
-										sbsrefstate->refelembyval,
-										sbsrefstate->refelemalign);
-	}
+	sbsrefstate->resnull = *op->resnull;
+	*op->resvalue = sbsroutines->assign(*op->resvalue, sbsrefstate);
+	*op->resnull = sbsrefstate->resnull;
 }
 
 /*
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 0409a40b82..b376a200c8 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -1548,8 +1548,10 @@ _copySubscriptingRef(const SubscriptingRef *from)
 
 	COPY_SCALAR_FIELD(refcontainertype);
 	COPY_SCALAR_FIELD(refelemtype);
+	COPY_SCALAR_FIELD(refassgntype);
 	COPY_SCALAR_FIELD(reftypmod);
 	COPY_SCALAR_FIELD(refcollid);
+	COPY_SCALAR_FIELD(refnestedfunc);
 	COPY_NODE_FIELD(refupperindexpr);
 	COPY_NODE_FIELD(reflowerindexpr);
 	COPY_NODE_FIELD(refexpr);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index e2d1b987bf..fe87f09ea2 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -274,8 +274,10 @@ _equalSubscriptingRef(const SubscriptingRef *a, const SubscriptingRef *b)
 {
 	COMPARE_SCALAR_FIELD(refcontainertype);
 	COMPARE_SCALAR_FIELD(refelemtype);
+	COMPARE_SCALAR_FIELD(refassgntype);
 	COMPARE_SCALAR_FIELD(reftypmod);
 	COMPARE_SCALAR_FIELD(refcollid);
+	COMPARE_SCALAR_FIELD(refnestedfunc);
 	COMPARE_NODE_FIELD(refupperindexpr);
 	COMPARE_NODE_FIELD(reflowerindexpr);
 	COMPARE_NODE_FIELD(refexpr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index e2f177515d..70c9736c46 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -1194,8 +1194,10 @@ _outSubscriptingRef(StringInfo str, const SubscriptingRef *node)
 
 	WRITE_OID_FIELD(refcontainertype);
 	WRITE_OID_FIELD(refelemtype);
+	WRITE_OID_FIELD(refassgntype);
 	WRITE_INT_FIELD(reftypmod);
 	WRITE_OID_FIELD(refcollid);
+	WRITE_OID_FIELD(refnestedfunc);
 	WRITE_NODE_FIELD(refupperindexpr);
 	WRITE_NODE_FIELD(reflowerindexpr);
 	WRITE_NODE_FIELD(refexpr);
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 42050ab719..1c9752c771 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -669,8 +669,10 @@ _readSubscriptingRef(void)
 
 	READ_OID_FIELD(refcontainertype);
 	READ_OID_FIELD(refelemtype);
+	READ_OID_FIELD(refassgntype);
 	READ_INT_FIELD(reftypmod);
 	READ_OID_FIELD(refcollid);
+	READ_OID_FIELD(refnestedfunc);
 	READ_NODE_FIELD(refupperindexpr);
 	READ_NODE_FIELD(reflowerindexpr);
 	READ_NODE_FIELD(refexpr);
diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index d24420c583..642ab27538 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -433,11 +433,13 @@ unknown_attribute(ParseState *pstate, Node *relref, const char *attname,
 static Node *
 transformIndirection(ParseState *pstate, A_Indirection *ind)
 {
-	Node	   *last_srf = pstate->p_last_srf;
-	Node	   *result = transformExprRecurse(pstate, ind->arg);
-	List	   *subscripts = NIL;
-	int			location = exprLocation(result);
-	ListCell   *i;
+	Node			  *last_srf = pstate->p_last_srf;
+	Node			  *result = transformExprRecurse(pstate, ind->arg);
+	SubscriptRoutines *sbsroutines;
+	SubscriptingRef   *sbsref;
+	List	          *subscripts = NIL;
+	int				  location = exprLocation(result);
+	ListCell		  *i;
 
 	/*
 	 * We have to split any field-selection operations apart from
@@ -465,13 +467,20 @@ transformIndirection(ParseState *pstate, A_Indirection *ind)
 
 			/* process subscripts before this field selection */
 			if (subscripts)
-				result = (Node *) transformContainerSubscripts(pstate,
-															   result,
-															   exprType(result),
-															   InvalidOid,
-															   exprTypmod(result),
-															   subscripts,
-															   NULL);
+			{
+				sbsref = transformContainerSubscripts(pstate,
+													  result,
+													  exprType(result),
+													  InvalidOid,
+													  exprTypmod(result),
+													  subscripts,
+													  NULL);
+
+				sbsroutines = getSubscriptingRoutines(sbsref->refcontainertype);
+				sbsref = sbsroutines->prepare(false, sbsref);
+				sbsroutines->validate(false, sbsref, pstate);
+				result = (Node *) sbsref;
+			}
 			subscripts = NIL;
 
 			newresult = ParseFuncOrColumn(pstate,
@@ -488,13 +497,20 @@ transformIndirection(ParseState *pstate, A_Indirection *ind)
 	}
 	/* process trailing subscripts, if any */
 	if (subscripts)
-		result = (Node *) transformContainerSubscripts(pstate,
-													   result,
-													   exprType(result),
-													   InvalidOid,
-													   exprTypmod(result),
-													   subscripts,
-													   NULL);
+	{
+		sbsref = transformContainerSubscripts(pstate,
+											  result,
+											  exprType(result),
+											  InvalidOid,
+											  exprTypmod(result),
+											  subscripts,
+											  NULL);
+
+		sbsroutines = getSubscriptingRoutines(sbsref->refcontainertype);
+		sbsref = sbsroutines->prepare(false, sbsref);
+		sbsroutines->validate(false, sbsref, pstate);
+		result = (Node *) sbsref;
+	}
 
 	return result;
 }
diff --git a/src/backend/parser/parse_node.c b/src/backend/parser/parse_node.c
index 6e98fe55fc..4f46d6310a 100644
--- a/src/backend/parser/parse_node.c
+++ b/src/backend/parser/parse_node.c
@@ -184,21 +184,12 @@ pcb_error_callback(void *arg)
  * transformContainerType()
  *		Identify the types involved in a subscripting operation for container
  *
- *
- * On entry, containerType/containerTypmod identify the type of the input value
- * to be subscripted (which could be a domain type).  These are modified if
- * necessary to identify the actual container type and typmod, and the
- * container's element type is returned.  An error is thrown if the input isn't
- * an array type.
+ * On entry, containerType/containerTypmod are modified if necessary to
+ * identify the actual container type and typmod.
  */
-Oid
+void
 transformContainerType(Oid *containerType, int32 *containerTypmod)
 {
-	Oid			origContainerType = *containerType;
-	Oid			elementType;
-	HeapTuple	type_tuple_container;
-	Form_pg_type type_struct_container;
-
 	/*
 	 * If the input is a domain, smash to base type, and extract the actual
 	 * typmod to be applied to the base type. Subscripting a domain is an
@@ -219,25 +210,6 @@ transformContainerType(Oid *containerType, int32 *containerTypmod)
 		*containerType = INT2ARRAYOID;
 	else if (*containerType == OIDVECTOROID)
 		*containerType = OIDARRAYOID;
-
-	/* Get the type tuple for the container */
-	type_tuple_container = SearchSysCache1(TYPEOID, ObjectIdGetDatum(*containerType));
-	if (!HeapTupleIsValid(type_tuple_container))
-		elog(ERROR, "cache lookup failed for type %u", *containerType);
-	type_struct_container = (Form_pg_type) GETSTRUCT(type_tuple_container);
-
-	/* needn't check typisdefined since this will fail anyway */
-
-	elementType = type_struct_container->typelem;
-	if (elementType == InvalidOid)
-		ereport(ERROR,
-				(errcode(ERRCODE_DATATYPE_MISMATCH),
-				 errmsg("cannot subscript type %s because it is not an array",
-						format_type_be(origContainerType))));
-
-	ReleaseSysCache(type_tuple_container);
-
-	return elementType;
 }
 
 /*
@@ -254,10 +226,15 @@ transformContainerType(Oid *containerType, int32 *containerTypmod)
  * container. We produce an expression that represents the new container value
  * with the source data inserted into the right part of the container.
  *
- * For both cases, if the source container is of a domain-over-array type,
- * the result is of the base array type or its element type; essentially,
- * we must fold a domain to its base type before applying subscripting.
- * (Note that int2vector and oidvector are treated as domains here.)
+ * For both cases, this function contains only general subscripting logic while
+ * type-specific logic (e.g. type verifications and coercion) is placed in
+ * separate procedures indicated by typsubshandler. There is only one exception
+ * for now about domain-over-container: if the source container is of a
+ * domain-over-container type, the result is of the base container type or its
+ * element type; essentially, we must fold a domain to its base type before
+ * applying subscripting. (Note that int2vector and oidvector are treated as
+ * domains here.) An error will appear in the case the current container type
+ * doesn't have a subscripting procedure.
  *
  * pstate			Parse state
  * containerBase	Already-transformed expression for the container as a whole
@@ -284,16 +261,12 @@ transformContainerSubscripts(ParseState *pstate,
 	bool		isSlice = false;
 	List	   *upperIndexpr = NIL;
 	List	   *lowerIndexpr = NIL;
+	List	   *indexprSlice = NIL;
 	ListCell   *idx;
 	SubscriptingRef *sbsref;
 
-	/*
-	 * Caller may or may not have bothered to determine elementType.  Note
-	 * that if the caller did do so, containerType/containerTypMod must be as
-	 * modified by transformContainerType, ie, smash domain to base type.
-	 */
-	if (!OidIsValid(elementType))
-		elementType = transformContainerType(&containerType, &containerTypMod);
+	/* Identify the actual container type and element type involved */
+	transformContainerType(&containerType, &containerTypMod);
 
 	/*
 	 * A list containing only simple subscripts refers to a single container
@@ -327,29 +300,6 @@ transformContainerSubscripts(ParseState *pstate,
 			if (ai->lidx)
 			{
 				subexpr = transformExpr(pstate, ai->lidx, pstate->p_expr_kind);
-				/* If it's not int4 already, try to coerce */
-				subexpr = coerce_to_target_type(pstate,
-												subexpr, exprType(subexpr),
-												INT4OID, -1,
-												COERCION_ASSIGNMENT,
-												COERCE_IMPLICIT_CAST,
-												-1);
-				if (subexpr == NULL)
-					ereport(ERROR,
-							(errcode(ERRCODE_DATATYPE_MISMATCH),
-							 errmsg("array subscript must have type integer"),
-							 parser_errposition(pstate, exprLocation(ai->lidx))));
-			}
-			else if (!ai->is_slice)
-			{
-				/* Make a constant 1 */
-				subexpr = (Node *) makeConst(INT4OID,
-											 -1,
-											 InvalidOid,
-											 sizeof(int32),
-											 Int32GetDatum(1),
-											 false,
-											 true); /* pass by value */
 			}
 			else
 			{
@@ -357,63 +307,23 @@ transformContainerSubscripts(ParseState *pstate,
 				subexpr = NULL;
 			}
 			lowerIndexpr = lappend(lowerIndexpr, subexpr);
+			indexprSlice = lappend(indexprSlice, ai);
 		}
 		else
 			Assert(ai->lidx == NULL && !ai->is_slice);
 
 		if (ai->uidx)
-		{
 			subexpr = transformExpr(pstate, ai->uidx, pstate->p_expr_kind);
-			/* If it's not int4 already, try to coerce */
-			subexpr = coerce_to_target_type(pstate,
-											subexpr, exprType(subexpr),
-											INT4OID, -1,
-											COERCION_ASSIGNMENT,
-											COERCE_IMPLICIT_CAST,
-											-1);
-			if (subexpr == NULL)
-				ereport(ERROR,
-						(errcode(ERRCODE_DATATYPE_MISMATCH),
-						 errmsg("array subscript must have type integer"),
-						 parser_errposition(pstate, exprLocation(ai->uidx))));
-		}
 		else
 		{
 			/* Slice with omitted upper bound, put NULL into the list */
 			Assert(isSlice && ai->is_slice);
 			subexpr = NULL;
 		}
+		subexpr = transformExpr(pstate, ai->uidx, pstate->p_expr_kind);
 		upperIndexpr = lappend(upperIndexpr, subexpr);
 	}
 
-	/*
-	 * If doing an array store, coerce the source value to the right type.
-	 * (This should agree with the coercion done by transformAssignedExpr.)
-	 */
-	if (assignFrom != NULL)
-	{
-		Oid			typesource = exprType(assignFrom);
-		Oid			typeneeded = isSlice ? containerType : elementType;
-		Node	   *newFrom;
-
-		newFrom = coerce_to_target_type(pstate,
-										assignFrom, typesource,
-										typeneeded, containerTypMod,
-										COERCION_ASSIGNMENT,
-										COERCE_IMPLICIT_CAST,
-										-1);
-		if (newFrom == NULL)
-			ereport(ERROR,
-					(errcode(ERRCODE_DATATYPE_MISMATCH),
-					 errmsg("array assignment requires type %s"
-							" but expression is of type %s",
-							format_type_be(typeneeded),
-							format_type_be(typesource)),
-					 errhint("You will need to rewrite or cast the expression."),
-					 parser_errposition(pstate, exprLocation(assignFrom))));
-		assignFrom = newFrom;
-	}
-
 	/*
 	 * Ready to build the SubscriptingRef node.
 	 */
@@ -422,17 +332,30 @@ transformContainerSubscripts(ParseState *pstate,
 		sbsref->refassgnexpr = (Expr *) assignFrom;
 
 	sbsref->refcontainertype = containerType;
-	sbsref->refelemtype = elementType;
 	sbsref->reftypmod = containerTypMod;
 	/* refcollid will be set by parse_collate.c */
 	sbsref->refupperindexpr = upperIndexpr;
 	sbsref->reflowerindexpr = lowerIndexpr;
+	sbsref->refindexprslice = indexprSlice;
 	sbsref->refexpr = (Expr *) containerBase;
-	sbsref->refassgnexpr = (Expr *) assignFrom;
 
 	return sbsref;
 }
 
+SubscriptRoutines*
+getSubscriptingRoutines(Oid containerType)
+{
+	RegProcedure typsubshandler = get_typsubsprocs(containerType);
+
+	if (!OidIsValid(typsubshandler))
+		ereport(ERROR,
+				(errcode(ERRCODE_DATATYPE_MISMATCH),
+				 errmsg("cannot subscript type %s because it does not support subscripting",
+						format_type_be(containerType))));
+
+	return (SubscriptRoutines *) OidFunctionCall0(typsubshandler);
+}
+
 /*
  * make_const
  *
diff --git a/src/backend/parser/parse_target.c b/src/backend/parser/parse_target.c
index 566c517837..d7483c6538 100644
--- a/src/backend/parser/parse_target.c
+++ b/src/backend/parser/parse_target.c
@@ -685,7 +685,7 @@ transformAssignmentIndirection(ParseState *pstate,
 							   Node *rhs,
 							   int location)
 {
-	Node	   *result;
+	Node	   *result = NULL;
 	List	   *subscripts = NIL;
 	bool		isSlice = false;
 	ListCell   *i;
@@ -848,27 +848,21 @@ transformAssignmentIndirection(ParseState *pstate,
 											 location);
 	}
 
-	/* base case: just coerce RHS to match target type ID */
-
-	result = coerce_to_target_type(pstate,
-								   rhs, exprType(rhs),
-								   targetTypeId, targetTypMod,
-								   COERCION_ASSIGNMENT,
-								   COERCE_IMPLICIT_CAST,
-								   -1);
-	if (result == NULL)
+	/*
+	 * Base case: just coerce RHS to match target type ID.
+	 * It's necessary only for field selection, since for
+	 * subscripting its custom code should define types.
+	 */
+	if (!targetIsSubscripting)
 	{
-		if (targetIsSubscripting)
-			ereport(ERROR,
-					(errcode(ERRCODE_DATATYPE_MISMATCH),
-					 errmsg("array assignment to \"%s\" requires type %s"
-							" but expression is of type %s",
-							targetName,
-							format_type_be(targetTypeId),
-							format_type_be(exprType(rhs))),
-					 errhint("You will need to rewrite or cast the expression."),
-					 parser_errposition(pstate, location)));
-		else
+		result = coerce_to_target_type(pstate,
+									   rhs, exprType(rhs),
+									   targetTypeId, targetTypMod,
+									   COERCION_ASSIGNMENT,
+									   COERCE_IMPLICIT_CAST,
+									   -1);
+
+		if (result == NULL)
 			ereport(ERROR,
 					(errcode(ERRCODE_DATATYPE_MISMATCH),
 					 errmsg("subfield \"%s\" is of type %s"
@@ -900,29 +894,42 @@ transformAssignmentSubscripts(ParseState *pstate,
 							  Node *rhs,
 							  int location)
 {
-	Node	   *result;
-	Oid			containerType;
-	int32		containerTypMod;
-	Oid			elementTypeId;
-	Oid			typeNeeded;
-	Oid			collationNeeded;
+	Node			  *result;
+	Oid				  containerType;
+	int32			  containerTypMod;
+	Oid				  collationNeeded;
+	SubscriptingRef   *sbsref;
+	SubscriptRoutines *sbsroutines;
 
 	Assert(subscripts != NIL);
 
 	/* Identify the actual array type and element type involved */
 	containerType = targetTypeId;
 	containerTypMod = targetTypMod;
-	elementTypeId = transformContainerType(&containerType, &containerTypMod);
 
-	/* Identify type that RHS must provide */
-	typeNeeded = isSlice ? containerType : elementTypeId;
+	/* process subscripts */
+	sbsref = transformContainerSubscripts(pstate,
+										  basenode,
+										  containerType,
+										  exprType(rhs),
+										  containerTypMod,
+										  subscripts,
+										  rhs);
+
+	sbsroutines = getSubscriptingRoutines(sbsref->refcontainertype);
+
+	/*
+	 * Let custom code provide necessary information about required types:
+	 * refelemtype and refassgntype
+	 */
+	sbsref = sbsroutines->prepare(rhs != NULL, sbsref);
 
 	/*
 	 * container normally has same collation as elements, but there's an
 	 * exception: we might be subscripting a domain over a container type. In
 	 * that case use collation of the base type.
 	 */
-	if (containerType == targetTypeId)
+	if (sbsref->refcontainertype == containerType)
 		collationNeeded = targetCollation;
 	else
 		collationNeeded = get_typcollation(containerType);
@@ -932,25 +939,22 @@ transformAssignmentSubscripts(ParseState *pstate,
 										 NULL,
 										 targetName,
 										 true,
-										 typeNeeded,
-										 containerTypMod,
+										 sbsref->refassgntype,
+										 sbsref->reftypmod,
 										 collationNeeded,
 										 indirection,
 										 next_indirection,
 										 rhs,
 										 location);
 
-	/* process subscripts */
-	result = (Node *) transformContainerSubscripts(pstate,
-												   basenode,
-												   containerType,
-												   elementTypeId,
-												   containerTypMod,
-												   subscripts,
-												   rhs);
+	/* Provide fully prepared subscripting information for custom validation */
+	sbsref->refassgnexpr = (Expr *) rhs;
+	sbsroutines->validate(rhs != NULL, sbsref, pstate);
+
+	result = (Node *) sbsref;
 
 	/* If target was a domain over container, need to coerce up to the domain */
-	if (containerType != targetTypeId)
+	if (sbsref->refcontainertype != targetTypeId)
 	{
 		Oid			resulttype = exprType(result);
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 15877e37a6..75f86d8d5b 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -7994,17 +7994,18 @@ get_rule_expr(Node *node, deparse_context *context,
 				if (need_parens)
 					appendStringInfoChar(buf, ')');
 
-				/*
-				 * If there's a refassgnexpr, we want to print the node in the
-				 * format "container[subscripts] := refassgnexpr".  This is
-				 * not legal SQL, so decompilation of INSERT or UPDATE
-				 * statements should always use processIndirection as part of
-				 * the statement-level syntax.  We should only see this when
-				 * EXPLAIN tries to print the targetlist of a plan resulting
-				 * from such a statement.
-				 */
-				if (sbsref->refassgnexpr)
+				if (IsAssignment(sbsref))
 				{
+					/*
+					 * If there's a refassgnexpr, we want to print the node in the
+					 * format "container[subscripts] := refassgnexpr". This is not
+					 * legal SQL, so decompilation of INSERT or UPDATE statements
+					 * should always use processIndirection as part of the
+					 * statement-level syntax.  We should only see this when
+					 * EXPLAIN tries to print the targetlist of a plan resulting
+					 * from such a statement.
+					 */
+
 					Node	   *refassgnexpr;
 
 					/*
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index f3bf413829..fb264a1e57 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -3273,6 +3273,29 @@ get_range_collation(Oid rangeOid)
 		return InvalidOid;
 }
 
+/*
+ * get_typsubshandler
+ *
+ *		Given the type OID, return the type's subscripting procedures, if any,
+ *		through pointers in arguments.
+ */
+RegProcedure
+get_typsubsprocs(Oid typid)
+{
+	HeapTuple		tp;
+
+	tp = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
+	if (HeapTupleIsValid(tp))
+	{
+		RegProcedure handler = ((Form_pg_type) GETSTRUCT(tp))->typsubshandler;
+		ReleaseSysCache(tp);
+
+		return handler;
+	}
+	else
+		return InvalidOid;
+}
+
 /*				---------- PG_INDEX CACHE ----------				 */
 
 /*
diff --git a/src/include/c.h b/src/include/c.h
index 2c61ca8aa8..d3bdefccf0 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -545,6 +545,8 @@ typedef struct
 	int			indx[MAXDIM];
 }			IntArray;
 
+#define MAX_SUBSCRIPT_DEPTH 12
+
 /* ----------------
  *		Variable-length datatypes all share the 'struct varlena' header.
  *
diff --git a/src/include/catalog/pg_type.h b/src/include/catalog/pg_type.h
index 7b37562648..ea237ec61d 100644
--- a/src/include/catalog/pg_type.h
+++ b/src/include/catalog/pg_type.h
@@ -221,6 +221,12 @@ CATALOG(pg_type,1247,TypeRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(71,TypeRelati
 	 */
 	Oid			typcollation BKI_DEFAULT(0) BKI_LOOKUP(pg_collation);
 
+	/*
+	 * Type specific subscripting logic. If typsubshandler is NULL, it means
+	 * that this type doesn't support subscripting.
+	 */
+	regproc		typsubshandler BKI_DEFAULT(-) BKI_LOOKUP(pg_proc);
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 
 	/*
@@ -349,7 +355,8 @@ extern ObjectAddress TypeCreate(Oid newTypeOid,
 								int32 typeMod,
 								int32 typNDims,
 								bool typeNotNull,
-								Oid typeCollation);
+								Oid typeCollation,
+								Oid subscriptingParseProcedure);
 
 extern void GenerateTypeDependencies(HeapTuple typeTuple,
 									 Relation typeCatalog,
diff --git a/src/include/executor/execExpr.h b/src/include/executor/execExpr.h
index dbe8649a57..06361e8da8 100644
--- a/src/include/executor/execExpr.h
+++ b/src/include/executor/execExpr.h
@@ -19,7 +19,7 @@
 
 /* forward references to avoid circularity */
 struct ExprEvalStep;
-struct SubscriptingRefState;
+struct SubscriptRoutines;
 
 /* Bits in ExprState->flags (see also execnodes.h for public flag bits): */
 /* expression's interpreter has been initialized */
@@ -654,17 +654,19 @@ typedef struct SubscriptingRefState
 	int16		refelemlength;	/* typlen of the container element type */
 	bool		refelembyval;	/* is the element type pass-by-value? */
 	char		refelemalign;	/* typalign of the element type */
+	void		*refopaque;		/* opaque data structure for implementation
+								   specific information */
 
 	/* numupper and upperprovided[] are filled at compile time */
 	/* at runtime, extracted subscript datums get stored in upperindex[] */
 	int			numupper;
-	bool		upperprovided[MAXDIM];
-	int			upperindex[MAXDIM];
+	bool		upperprovided[MAX_SUBSCRIPT_DEPTH];
+	Datum		upperindex[MAX_SUBSCRIPT_DEPTH];
 
 	/* similarly for lower indexes, if any */
 	int			numlower;
-	bool		lowerprovided[MAXDIM];
-	int			lowerindex[MAXDIM];
+	bool		lowerprovided[MAX_SUBSCRIPT_DEPTH];
+	Datum		lowerindex[MAX_SUBSCRIPT_DEPTH];
 
 	/* subscript expressions get evaluated into here */
 	Datum		subscriptvalue;
@@ -677,6 +679,9 @@ typedef struct SubscriptingRefState
 	/* if we have a nested assignment, SBSREF_OLD puts old value here */
 	Datum		prevvalue;
 	bool		prevnull;
+
+	bool		resnull;
+	struct SubscriptRoutines *sbsroutines;
 } SubscriptingRefState;
 
 
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index d73be2ad46..0cd7763683 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -417,20 +417,28 @@ typedef struct SubscriptingRef
 	Expr		xpr;
 	Oid			refcontainertype;	/* type of the container proper */
 	Oid			refelemtype;	/* type of the container elements */
+	Oid			refassgntype;		/* type of assignment expr that is required */
 	int32		reftypmod;		/* typmod of the container (and elements too) */
 	Oid			refcollid;		/* OID of collation, or InvalidOid if none */
+	Oid			refnestedfunc;		/* OID of type-specific function to handle nested assignment */
 	List	   *refupperindexpr;	/* expressions that evaluate to upper
 									 * container indexes */
 	List	   *reflowerindexpr;	/* expressions that evaluate to lower
 									 * container indexes, or NIL for single
 									 * container element */
+	List       *refindexprslice;    /* whether or not related indexpr from
+									 * reflowerindexpr is a slice */
 	Expr	   *refexpr;		/* the expression that evaluates to a
 								 * container value */
 
 	Expr	   *refassgnexpr;	/* expression for the source value, or NULL if
 								 * fetch */
+	void	   *refopaque;		/* opaque data structure for implementation
+								   specific information */
 } SubscriptingRef;
 
+#define IsAssignment(expr) ( ((SubscriptingRef*) expr)->refassgnexpr != NULL )
+
 /*
  * CoercionContext - distinguishes the allowed set of type casts
  *
diff --git a/src/include/nodes/subscripting.h b/src/include/nodes/subscripting.h
new file mode 100644
index 0000000000..1800d5ecf5
--- /dev/null
+++ b/src/include/nodes/subscripting.h
@@ -0,0 +1,42 @@
+/*-------------------------------------------------------------------------
+ *
+ * subscripting.h
+ *		API for generic type subscripting
+ *
+ * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/nodes/subscripting.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SUBSCRIPTING_H
+#define SUBSCRIPTING_H
+
+#include "parser/parse_node.h"
+#include "nodes/primnodes.h"
+
+struct ParseState;
+struct SubscriptingRefState;
+
+/* Callback function signatures --- see xsubscripting.sgml for more info. */
+typedef SubscriptingRef * (*SubscriptingPrepare) (bool isAssignment, SubscriptingRef *sbsef);
+
+typedef SubscriptingRef * (*SubscriptingValidate) (bool isAssignment, SubscriptingRef *sbsef,
+												   struct ParseState *pstate);
+
+typedef Datum (*SubscriptingFetch) (Datum source, struct SubscriptingRefState *sbsrefstate);
+
+typedef Datum (*SubscriptingAssign) (Datum source, struct SubscriptingRefState *sbrsefstate);
+
+typedef struct SubscriptRoutines
+{
+	SubscriptingPrepare		prepare;
+	SubscriptingValidate	validate;
+	SubscriptingFetch		fetch;
+	SubscriptingAssign		assign;
+
+} SubscriptRoutines;
+
+
+#endif							/* SUBSCRIPTING_H */
diff --git a/src/include/parser/parse_node.h b/src/include/parser/parse_node.h
index d25819aa28..b4736206d1 100644
--- a/src/include/parser/parse_node.h
+++ b/src/include/parser/parse_node.h
@@ -15,6 +15,7 @@
 #define PARSE_NODE_H
 
 #include "nodes/parsenodes.h"
+#include "nodes/subscripting.h"
 #include "utils/queryenvironment.h"
 #include "utils/relcache.h"
 
@@ -313,7 +314,9 @@ extern void setup_parser_errposition_callback(ParseCallbackState *pcbstate,
 											  ParseState *pstate, int location);
 extern void cancel_parser_errposition_callback(ParseCallbackState *pcbstate);
 
-extern Oid	transformContainerType(Oid *containerType, int32 *containerTypmod);
+extern Var *make_var(ParseState *pstate, RangeTblEntry *rte, int attrno,
+					 int location);
+extern void	transformContainerType(Oid *containerType, int32 *containerTypmod);
 
 extern SubscriptingRef *transformContainerSubscripts(ParseState *pstate,
 													 Node *containerBase,
@@ -322,6 +325,7 @@ extern SubscriptingRef *transformContainerSubscripts(ParseState *pstate,
 													 int32 containerTypMod,
 													 List *indirection,
 													 Node *assignFrom);
+extern SubscriptRoutines *getSubscriptingRoutines(Oid containerType);
 extern Const *make_const(ParseState *pstate, Value *value, int location);
 
 #endif							/* PARSE_NODE_H */
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index fecfe1f4f6..8fc570d2e1 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -183,6 +183,7 @@ extern char *get_namespace_name(Oid nspid);
 extern char *get_namespace_name_or_temp(Oid nspid);
 extern Oid	get_range_subtype(Oid rangeOid);
 extern Oid	get_range_collation(Oid rangeOid);
+extern RegProcedure get_typsubsprocs(Oid typid);
 extern Oid	get_index_column_opclass(Oid index_oid, int attno);
 extern bool get_index_isreplident(Oid index_oid);
 extern bool get_index_isvalid(Oid index_oid);
-- 
2.21.0

>From f57215d2c552f38183c799b55fb97bf85435379d Mon Sep 17 00:00:00 2001
From: erthalion <9erthali...@gmail.com>
Date: Fri, 1 Feb 2019 11:38:52 +0100
Subject: [PATCH v35 2/5] Subscripting for array

Subscripting implementation for array data types. It includes all array
specific parts, that were removed from the generalized code. Note, that
for some array-like data types it's not necessary to assign
array_subscript_handler explicitely, since it's done in Catalog.pm

Reviewed-by: Tom Lane, Arthur Zakirov
---
 src/backend/catalog/Catalog.pm        |   1 +
 src/backend/catalog/heap.c            |   2 +-
 src/backend/commands/typecmds.c       |   8 +-
 src/backend/executor/execExprInterp.c |  15 +-
 src/backend/nodes/nodeFuncs.c         |   2 +-
 src/backend/parser/parse_node.c       |  11 -
 src/backend/parser/parse_target.c     |   4 +-
 src/backend/utils/adt/arrayfuncs.c    | 289 ++++++++++++++++++++++++++
 src/include/catalog/pg_proc.dat       |   7 +
 src/include/catalog/pg_type.dat       |  30 ++-
 src/test/regress/expected/arrays.out  |  12 +-
 src/test/regress/sql/arrays.sql       |   4 +-
 12 files changed, 346 insertions(+), 39 deletions(-)

diff --git a/src/backend/catalog/Catalog.pm b/src/backend/catalog/Catalog.pm
index dd39a086ce..b4dfa26518 100644
--- a/src/backend/catalog/Catalog.pm
+++ b/src/backend/catalog/Catalog.pm
@@ -384,6 +384,7 @@ sub GenerateArrayTypes
 		# Arrays require INT alignment, unless the element type requires
 		# DOUBLE alignment.
 		$array_type{typalign} = $elem_type->{typalign} eq 'd' ? 'd' : 'i';
+		$array_type{typsubshandler} = 'array_subscript_handler';
 
 		# Fill in the rest of the array entry's fields.
 		foreach my $column (@$pgtype_schema)
diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index 4d552589ae..4703d8076b 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -1372,7 +1372,7 @@ heap_create_with_catalog(const char *relname,
 				   0,			/* array dimensions for typBaseType */
 				   false,		/* Type NOT NULL */
 				   InvalidOid,  /* rowtypes never have a collation */
-				   0);	/* array implementation */
+				   F_ARRAY_SUBSCRIPT_HANDLER);	/* array implementation */
 
 		pfree(relarrayname);
 	}
diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c
index 33d4fb401d..596c6cf3ca 100644
--- a/src/backend/commands/typecmds.c
+++ b/src/backend/commands/typecmds.c
@@ -618,7 +618,7 @@ DefineType(ParseState *pstate, List *names, List *parameters)
 			   0,				/* Array dimensions of typbasetype */
 			   false,			/* Type NOT NULL */
 			   collation,		/* type's collation */
-			   0);
+			   F_ARRAY_SUBSCRIPT_HANDLER);
 
 	pfree(array_type);
 
@@ -1065,7 +1065,7 @@ DefineDomain(CreateDomainStmt *stmt)
 			   0,				/* Array dimensions of typbasetype */
 			   false,			/* Type NOT NULL */
 			   domaincoll,		/* type's collation */
-			   0); /* array subscripting implementation */
+			   F_ARRAY_SUBSCRIPT_HANDLER); /* array subscripting implementation */
 
 	pfree(domainArrayName);
 
@@ -1222,7 +1222,7 @@ DefineEnum(CreateEnumStmt *stmt)
 			   0,				/* Array dimensions of typbasetype */
 			   false,			/* Type NOT NULL */
 			   InvalidOid,		/* type's collation */
-			   0);	/* array subscripting implementation */
+			   F_ARRAY_SUBSCRIPT_HANDLER);	/* array subscripting implementation */
 
 	pfree(enumArrayName);
 
@@ -1555,7 +1555,7 @@ DefineRange(CreateRangeStmt *stmt)
 			   0,				/* Array dimensions of typbasetype */
 			   false,			/* Type NOT NULL */
 			   InvalidOid,		/* typcollation */
-			   0);	/* array subscripting implementation */
+			   F_ARRAY_SUBSCRIPT_HANDLER);	/* array subscripting implementation */
 
 	pfree(rangeArrayName);
 
diff --git a/src/backend/executor/execExprInterp.c b/src/backend/executor/execExprInterp.c
index 838bb4d005..b87daf65e0 100644
--- a/src/backend/executor/execExprInterp.c
+++ b/src/backend/executor/execExprInterp.c
@@ -3155,7 +3155,7 @@ ExecEvalSubscriptingRef(ExprState *state, ExprEvalStep *op)
 		if (sbsrefstate->isassignment)
 			ereport(ERROR,
 					(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
-					 errmsg("array subscript in assignment must not be null")));
+					 errmsg("subscript in assignment must not be null")));
 		*op->resnull = true;
 		return false;
 	}
@@ -3227,9 +3227,20 @@ ExecEvalSubscriptingRefOld(ExprState *state, ExprEvalStep *op)
 void
 ExecEvalSubscriptingRefAssign(ExprState *state, ExprEvalStep *op)
 {
-	SubscriptingRefState *sbsrefstate = op->d.sbsref_subscript.state;
+	SubscriptingRefState *sbsrefstate = op->d.sbsref.state;
 	SubscriptRoutines	 *sbsroutines = sbsrefstate->sbsroutines;
 
+	/*
+	 * For an assignment to a fixed-length container type, both the original
+	 * container and the value to be assigned into it must be non-NULL, else we
+	 * punt and return the original container.
+	 */
+	if (sbsrefstate->refattrlength > 0)
+	{
+		if (*op->resnull || sbsrefstate->replacenull)
+			return;
+	}
+
 	sbsrefstate->resnull = *op->resnull;
 	*op->resvalue = sbsroutines->assign(*op->resvalue, sbsrefstate);
 	*op->resnull = sbsrefstate->resnull;
diff --git a/src/backend/nodes/nodeFuncs.c b/src/backend/nodes/nodeFuncs.c
index 9ce8f43385..0fd9d8b110 100644
--- a/src/backend/nodes/nodeFuncs.c
+++ b/src/backend/nodes/nodeFuncs.c
@@ -70,7 +70,7 @@ exprType(const Node *expr)
 				const SubscriptingRef *sbsref = (const SubscriptingRef *) expr;
 
 				/* slice and/or store operations yield the container type */
-				if (sbsref->reflowerindexpr || sbsref->refassgnexpr)
+				if (IsAssignment(sbsref) || sbsref->reflowerindexpr)
 					type = sbsref->refcontainertype;
 				else
 					type = sbsref->refelemtype;
diff --git a/src/backend/parser/parse_node.c b/src/backend/parser/parse_node.c
index 4f46d6310a..d1c4ea8573 100644
--- a/src/backend/parser/parse_node.c
+++ b/src/backend/parser/parse_node.c
@@ -309,17 +309,6 @@ transformContainerSubscripts(ParseState *pstate,
 			lowerIndexpr = lappend(lowerIndexpr, subexpr);
 			indexprSlice = lappend(indexprSlice, ai);
 		}
-		else
-			Assert(ai->lidx == NULL && !ai->is_slice);
-
-		if (ai->uidx)
-			subexpr = transformExpr(pstate, ai->uidx, pstate->p_expr_kind);
-		else
-		{
-			/* Slice with omitted upper bound, put NULL into the list */
-			Assert(isSlice && ai->is_slice);
-			subexpr = NULL;
-		}
 		subexpr = transformExpr(pstate, ai->uidx, pstate->p_expr_kind);
 		upperIndexpr = lappend(upperIndexpr, subexpr);
 	}
diff --git a/src/backend/parser/parse_target.c b/src/backend/parser/parse_target.c
index d7483c6538..0161d0f540 100644
--- a/src/backend/parser/parse_target.c
+++ b/src/backend/parser/parse_target.c
@@ -685,7 +685,7 @@ transformAssignmentIndirection(ParseState *pstate,
 							   Node *rhs,
 							   int location)
 {
-	Node	   *result = NULL;
+	Node	   *result;
 	List	   *subscripts = NIL;
 	bool		isSlice = false;
 	ListCell   *i;
@@ -873,6 +873,8 @@ transformAssignmentIndirection(ParseState *pstate,
 					 errhint("You will need to rewrite or cast the expression."),
 					 parser_errposition(pstate, location)));
 	}
+	else
+		result = rhs;
 
 	return result;
 }
diff --git a/src/backend/utils/adt/arrayfuncs.c b/src/backend/utils/adt/arrayfuncs.c
index 392445ea03..21bd5882b0 100644
--- a/src/backend/utils/adt/arrayfuncs.c
+++ b/src/backend/utils/adt/arrayfuncs.c
@@ -25,14 +25,20 @@
 #include "nodes/supportnodes.h"
 #include "optimizer/optimizer.h"
 #include "port/pg_bitutils.h"
+#include "nodes/makefuncs.h"
+#include "executor/execExpr.h"
 #include "utils/array.h"
 #include "utils/arrayaccess.h"
 #include "utils/builtins.h"
 #include "utils/datum.h"
+#include "utils/fmgroids.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
 #include "utils/selfuncs.h"
+#include "utils/syscache.h"
 #include "utils/typcache.h"
+#include "parser/parse_node.h"
+#include "parser/parse_coerce.h"
 
 
 /*
@@ -159,7 +165,14 @@ static int	width_bucket_array_variable(Datum operand,
 										ArrayType *thresholds,
 										Oid collation,
 										TypeCacheEntry *typentry);
+static SubscriptingRef *array_subscript_prepare(bool isAssignment, SubscriptingRef *sbsref);
+static SubscriptingRef *array_subscript_validate(bool isAssignment, SubscriptingRef *sbsref,
+												 ParseState *pstate);
 
+static Datum array_subscript_fetch(Datum containerSource,
+								   SubscriptingRefState *sbstate);
+static Datum array_subscript_assign(Datum containerSource,
+									SubscriptingRefState *sbstate);
 
 /*
  * array_in :
@@ -6626,3 +6639,279 @@ width_bucket_array_variable(Datum operand,
 
 	return left;
 }
+
+/*
+ * Perform an actual data extraction or modification for the array
+ * subscripting. As a result the extracted Datum or the modified containers
+ * value will be returned.
+ */
+Datum
+array_subscript_assign(Datum containerSource, SubscriptingRefState *sbstate)
+{
+	bool						is_slice = (sbstate->numlower != 0);
+	IntArray					u_index, l_index;
+	bool						eisnull = sbstate->resnull;
+	int							i = 0;
+
+	if (sbstate->refelemlength == 0)
+	{
+		/* do one-time catalog lookups for type info */
+		get_typlenbyvalalign(sbstate->refelemtype,
+							 &sbstate->refelemlength,
+							 &sbstate->refelembyval,
+							 &sbstate->refelemalign);
+	}
+
+	for(i = 0; i < sbstate->numupper; i++)
+		u_index.indx[i] = DatumGetInt32(sbstate->upperindex[i]);
+
+	if (is_slice)
+	{
+		for(i = 0; i < sbstate->numlower; i++)
+			l_index.indx[i] = DatumGetInt32(sbstate->lowerindex[i]);
+	}
+
+	/*
+	 * For assignment to varlena arrays, we handle a NULL original array
+	 * by substituting an empty (zero-dimensional) array; insertion of the
+	 * new element will result in a singleton array value.  It does not
+	 * matter whether the new element is NULL.
+	 */
+	if (eisnull)
+	{
+		containerSource = PointerGetDatum(construct_empty_array(sbstate->refelemtype));
+		sbstate->resnull = false;
+		eisnull = false;
+	}
+
+	if (!is_slice)
+		return array_set_element(containerSource, sbstate->numupper,
+								 u_index.indx,
+								 sbstate->replacevalue,
+								 sbstate->replacenull,
+								 sbstate->refattrlength,
+								 sbstate->refelemlength,
+								 sbstate->refelembyval,
+								 sbstate->refelemalign);
+	else
+		return array_set_slice(containerSource, sbstate->numupper,
+							   u_index.indx, l_index.indx,
+							   sbstate->upperprovided,
+							   sbstate->lowerprovided,
+							   sbstate->replacevalue,
+							   sbstate->replacenull,
+							   sbstate->refattrlength,
+							   sbstate->refelemlength,
+							   sbstate->refelembyval,
+							   sbstate->refelemalign);
+}
+
+Datum
+array_subscript_fetch(Datum containerSource, SubscriptingRefState *sbstate)
+{
+	bool							is_slice = (sbstate->numlower != 0);
+	IntArray						u_index, l_index;
+	int								i = 0;
+
+	if (sbstate->refelemlength == 0)
+	{
+		/* do one-time catalog lookups for type info */
+		get_typlenbyvalalign(sbstate->refelemtype,
+							 &sbstate->refelemlength,
+							 &sbstate->refelembyval,
+							 &sbstate->refelemalign);
+	}
+
+	for(i = 0; i < sbstate->numupper; i++)
+		u_index.indx[i] = DatumGetInt32(sbstate->upperindex[i]);
+
+	if (is_slice)
+	{
+		for(i = 0; i < sbstate->numlower; i++)
+			l_index.indx[i] = DatumGetInt32(sbstate->lowerindex[i]);
+	}
+
+	if (!is_slice)
+		return array_get_element(containerSource, sbstate->numupper,
+								 u_index.indx,
+								 sbstate->refattrlength,
+								 sbstate->refelemlength,
+								 sbstate->refelembyval,
+								 sbstate->refelemalign,
+								 &sbstate->resnull);
+	else
+		return array_get_slice(containerSource, sbstate->numupper,
+							   u_index.indx, l_index.indx,
+							   sbstate->upperprovided,
+							   sbstate->lowerprovided,
+							   sbstate->refattrlength,
+							   sbstate->refelemlength,
+							   sbstate->refelembyval,
+							   sbstate->refelemalign);
+}
+
+/*
+ * Handle array-type subscripting logic.
+ */
+Datum
+array_subscript_handler(PG_FUNCTION_ARGS)
+{
+	SubscriptRoutines *sbsroutines = (SubscriptRoutines *)
+									 palloc(sizeof(SubscriptRoutines));
+
+	sbsroutines->prepare = array_subscript_prepare;
+	sbsroutines->validate = array_subscript_validate;
+	sbsroutines->fetch = array_subscript_fetch;
+	sbsroutines->assign = array_subscript_assign;
+
+	PG_RETURN_POINTER(sbsroutines);
+}
+
+SubscriptingRef *
+array_subscript_prepare(bool isAssignment, SubscriptingRef *sbsref)
+{
+	Oid					array_type = sbsref->refcontainertype;
+	HeapTuple			type_tuple_container;
+	Form_pg_type		type_struct_container;
+	bool				is_slice = sbsref->reflowerindexpr != NIL;
+
+	/* Get the type tuple for the container */
+	type_tuple_container = SearchSysCache1(TYPEOID, ObjectIdGetDatum(array_type));
+	if (!HeapTupleIsValid(type_tuple_container))
+		elog(ERROR, "cache lookup failed for type %u", array_type);
+	type_struct_container = (Form_pg_type) GETSTRUCT(type_tuple_container);
+
+	/* needn't check typisdefined since this will fail anyway */
+	sbsref->refelemtype = type_struct_container->typelem;
+
+	/* Identify type that RHS must provide */
+	if (isAssignment)
+		sbsref->refassgntype = is_slice ? sbsref->refcontainertype : sbsref->refelemtype;
+
+	ReleaseSysCache(type_tuple_container);
+
+	return sbsref;
+}
+
+SubscriptingRef *
+array_subscript_validate(bool isAssignment, SubscriptingRef *sbsref,
+					  ParseState *pstate)
+{
+	bool				is_slice = sbsref->reflowerindexpr != NIL;
+	Oid					typeneeded = InvalidOid,
+						typesource = InvalidOid;
+	Node				*new_from;
+	Node				*subexpr;
+	List				*upperIndexpr = NIL;
+	List				*lowerIndexpr = NIL;
+	ListCell			*u, *l, *s;
+
+	foreach(u, sbsref->refupperindexpr)
+	{
+		subexpr = (Node *) lfirst(u);
+
+		if (subexpr == NULL)
+		{
+			upperIndexpr = lappend(upperIndexpr, subexpr);
+			continue;
+		}
+
+		subexpr = coerce_to_target_type(pstate,
+										subexpr, exprType(subexpr),
+										INT4OID, -1,
+										COERCION_ASSIGNMENT,
+										COERCE_IMPLICIT_CAST,
+										-1);
+		if (subexpr == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+					 errmsg("array subscript must have type integer"),
+					 parser_errposition(pstate, exprLocation(subexpr))));
+
+		upperIndexpr = lappend(upperIndexpr, subexpr);
+	}
+
+	sbsref->refupperindexpr = upperIndexpr;
+
+	forboth(l, sbsref->reflowerindexpr, s, sbsref->refindexprslice)
+	{
+		A_Indices *ai = (A_Indices *) lfirst(s);
+		subexpr = (Node *) lfirst(l);
+
+		if (subexpr == NULL && !ai->is_slice)
+		{
+			/* Make a constant 1 */
+			subexpr = (Node *) makeConst(INT4OID,
+										 -1,
+										 InvalidOid,
+										 sizeof(int32),
+										 Int32GetDatum(1),
+										 false,
+										 true);		/* pass by value */
+		}
+
+		if (subexpr == NULL)
+		{
+			lowerIndexpr = lappend(lowerIndexpr, subexpr);
+			continue;
+		}
+
+		subexpr = coerce_to_target_type(pstate,
+										subexpr, exprType(subexpr),
+										INT4OID, -1,
+										COERCION_ASSIGNMENT,
+										COERCE_IMPLICIT_CAST,
+										-1);
+		if (subexpr == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+					 errmsg("array subscript must have type integer"),
+					 parser_errposition(pstate, exprLocation(subexpr))));
+
+		lowerIndexpr = lappend(lowerIndexpr, subexpr);
+	}
+
+	sbsref->reflowerindexpr = lowerIndexpr;
+
+	if (isAssignment)
+	{
+		SubscriptingRef *assignRef = (SubscriptingRef *) sbsref;
+		Node *assignExpr = (Node *) assignRef->refassgnexpr;
+
+		typesource = exprType(assignExpr);
+		typeneeded = is_slice ? sbsref->refcontainertype : sbsref->refelemtype;
+		new_from = coerce_to_target_type(pstate,
+										assignExpr, typesource,
+										typeneeded, sbsref->reftypmod,
+										COERCION_ASSIGNMENT,
+										COERCE_IMPLICIT_CAST,
+										-1);
+		if (new_from == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+					 errmsg("array assignment requires type %s"
+							" but expression is of type %s",
+							format_type_be(sbsref->refelemtype),
+							format_type_be(typesource)),
+				 errhint("You will need to rewrite or cast the expression."),
+					 parser_errposition(pstate, exprLocation(assignExpr))));
+		assignRef->refassgnexpr = (Expr *) new_from;
+	}
+
+	sbsref->refnestedfunc = F_ARRAY_SUBSCRIPT_HANDLER;
+
+	/* Verify subscript list lengths are within limit */
+	if (list_length(sbsref->refupperindexpr) > MAXDIM)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
+						list_length(sbsref->refupperindexpr), MAXDIM)));
+
+	if (list_length(sbsref->reflowerindexpr) > MAXDIM)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("number of array dimensions (%d) exceeds the maximum allowed (%d)",
+						list_length(sbsref->reflowerindexpr), MAXDIM)));
+
+	return sbsref;
+}
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index f48f5fb4d9..2c6aa65bf8 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10898,6 +10898,13 @@
   proargnames => '{max_data_alignment,database_block_size,blocks_per_segment,wal_block_size,bytes_per_wal_segment,max_identifier_length,max_index_columns,max_toast_chunk_size,large_object_chunk_size,float8_pass_by_value,data_page_checksum_version}',
   prosrc => 'pg_control_init' },
 
+{ oid => '6099',
+  descr => 'Array subscripting logic',
+  proname => 'array_subscript_handler',
+  prorettype => 'internal',
+  proargtypes => 'internal',
+  prosrc => 'array_subscript_handler' },
+
 # collation management functions
 { oid => '3445', descr => 'import collations from operating system',
   proname => 'pg_import_system_collations', procost => '100',
diff --git a/src/include/catalog/pg_type.dat b/src/include/catalog/pg_type.dat
index b2cec07416..21489a02ae 100644
--- a/src/include/catalog/pg_type.dat
+++ b/src/include/catalog/pg_type.dat
@@ -54,7 +54,8 @@
   typname => 'name', typlen => 'NAMEDATALEN', typbyval => 'f',
   typcategory => 'S', typelem => 'char', typinput => 'namein',
   typoutput => 'nameout', typreceive => 'namerecv', typsend => 'namesend',
-  typalign => 'c', typcollation => 'C' },
+  typalign => 'c', typcollation => 'C',
+  typsubshandler => 'array_subscript_handler' },
 { oid => '20', array_type_oid => '1016',
   descr => '~18 digit integer, 8-byte storage',
   typname => 'int8', typlen => '8', typbyval => 'FLOAT8PASSBYVAL',
@@ -70,7 +71,7 @@
   typname => 'int2vector', typlen => '-1', typbyval => 'f', typcategory => 'A',
   typelem => 'int2', typinput => 'int2vectorin', typoutput => 'int2vectorout',
   typreceive => 'int2vectorrecv', typsend => 'int2vectorsend',
-  typalign => 'i' },
+  typalign => 'i', typsubshandler => 'array_subscript_handler' },
 { oid => '23', array_type_oid => '1007',
   descr => '-2 billion to 2 billion integer, 4-byte storage',
   typname => 'int4', typlen => '4', typbyval => 't', typcategory => 'N',
@@ -109,7 +110,8 @@
   descr => 'array of oids, used in system tables',
   typname => 'oidvector', typlen => '-1', typbyval => 'f', typcategory => 'A',
   typelem => 'oid', typinput => 'oidvectorin', typoutput => 'oidvectorout',
-  typreceive => 'oidvectorrecv', typsend => 'oidvectorsend', typalign => 'i' },
+  typreceive => 'oidvectorrecv', typsend => 'oidvectorsend', typalign => 'i',
+  typsubshandler => 'array_subscript_handler' },
 
 # hand-built rowtype entries for bootstrapped catalogs
 # NB: OIDs assigned here must match the BKI_ROWTYPE_OID declarations
@@ -188,32 +190,37 @@
   descr => 'geometric point \'(x, y)\'',
   typname => 'point', typlen => '16', typbyval => 'f', typcategory => 'G',
   typelem => 'float8', typinput => 'point_in', typoutput => 'point_out',
-  typreceive => 'point_recv', typsend => 'point_send', typalign => 'd' },
+  typreceive => 'point_recv', typsend => 'point_send', typalign => 'd',
+  typsubshandler => 'array_subscript_handler' },
 { oid => '601', array_type_oid => '1018',
   descr => 'geometric line segment \'(pt1,pt2)\'',
   typname => 'lseg', typlen => '32', typbyval => 'f', typcategory => 'G',
   typelem => 'point', typinput => 'lseg_in', typoutput => 'lseg_out',
-  typreceive => 'lseg_recv', typsend => 'lseg_send', typalign => 'd' },
+  typreceive => 'lseg_recv', typsend => 'lseg_send', typalign => 'd',
+  typsubshandler => 'array_subscript_handler' },
 { oid => '602', array_type_oid => '1019',
   descr => 'geometric path \'(pt1,...)\'',
   typname => 'path', typlen => '-1', typbyval => 'f', typcategory => 'G',
   typinput => 'path_in', typoutput => 'path_out', typreceive => 'path_recv',
-  typsend => 'path_send', typalign => 'd', typstorage => 'x' },
+  typsend => 'path_send', typalign => 'd', typstorage => 'x',
+  typsubshandler => 'array_subscript_handler' },
 { oid => '603', array_type_oid => '1020',
   descr => 'geometric box \'(lower left,upper right)\'',
   typname => 'box', typlen => '32', typbyval => 'f', typcategory => 'G',
   typdelim => ';', typelem => 'point', typinput => 'box_in',
   typoutput => 'box_out', typreceive => 'box_recv', typsend => 'box_send',
-  typalign => 'd' },
+  typalign => 'd', typsubshandler => 'array_subscript_handler' },
 { oid => '604', array_type_oid => '1027',
   descr => 'geometric polygon \'(pt1,...)\'',
   typname => 'polygon', typlen => '-1', typbyval => 'f', typcategory => 'G',
   typinput => 'poly_in', typoutput => 'poly_out', typreceive => 'poly_recv',
-  typsend => 'poly_send', typalign => 'd', typstorage => 'x' },
+  typsend => 'poly_send', typalign => 'd', typstorage => 'x',
+  typsubshandler => 'array_subscript_handler' },
 { oid => '628', array_type_oid => '629', descr => 'geometric line',
   typname => 'line', typlen => '24', typbyval => 'f', typcategory => 'G',
   typelem => 'float8', typinput => 'line_in', typoutput => 'line_out',
-  typreceive => 'line_recv', typsend => 'line_send', typalign => 'd' },
+  typreceive => 'line_recv', typsend => 'line_send', typalign => 'd',
+  typsubshandler => 'array_subscript_handler' },
 
 # OIDS 700 - 799
 
@@ -272,7 +279,7 @@
 { oid => '1033', array_type_oid => '1034', descr => 'access control list',
   typname => 'aclitem', typlen => '12', typbyval => 'f', typcategory => 'U',
   typinput => 'aclitemin', typoutput => 'aclitemout', typreceive => '-',
-  typsend => '-', typalign => 'i' },
+  typsend => '-', typalign => 'i', typsubshandler => 'array_subscript_handler' },
 { oid => '1042', array_type_oid => '1014',
   descr => 'char(length), blank-padded string, fixed storage length',
   typname => 'bpchar', typlen => '-1', typbyval => 'f', typcategory => 'S',
@@ -311,7 +318,8 @@
   typcategory => 'D', typispreferred => 't', typinput => 'timestamptz_in',
   typoutput => 'timestamptz_out', typreceive => 'timestamptz_recv',
   typsend => 'timestamptz_send', typmodin => 'timestamptztypmodin',
-  typmodout => 'timestamptztypmodout', typalign => 'd' },
+  typmodout => 'timestamptztypmodout', typalign => 'd',
+  typsubshandler => 'array_subscript_handler' },
 { oid => '1186', array_type_oid => '1187',
   descr => '@ <number> <units>, time interval',
   typname => 'interval', typlen => '16', typbyval => 'f', typcategory => 'T',
diff --git a/src/test/regress/expected/arrays.out b/src/test/regress/expected/arrays.out
index f9d9ad6aef..46b8cd4b98 100644
--- a/src/test/regress/expected/arrays.out
+++ b/src/test/regress/expected/arrays.out
@@ -190,9 +190,9 @@ select ('[0:2][0:2]={{1,2,3},{4,5,6},{7,8,9}}'::int[])[1:2][2];
 --
 -- check subscription corner cases
 --
--- More subscripts than MAXDIMS(6)
-SELECT ('{}'::int[])[1][2][3][4][5][6][7];
-ERROR:  number of array dimensions (7) exceeds the maximum allowed (6)
+-- More subscripts than MAXDIMS(12)
+SELECT ('{}'::int[])[1][2][3][4][5][6][7][8][9][10][11][12][13];
+ERROR:  number of array dimensions (13) exceeds the maximum allowed (6)
 -- NULL index yields NULL when selecting
 SELECT ('{{{1},{2},{3}},{{4},{5},{6}}}'::int[])[1][NULL][1];
  int4 
@@ -216,15 +216,15 @@ SELECT ('{{{1},{2},{3}},{{4},{5},{6}}}'::int[])[1][1:NULL][1];
 UPDATE arrtest
   SET c[NULL] = '{"can''t assign"}'
   WHERE array_dims(c) is not null;
-ERROR:  array subscript in assignment must not be null
+ERROR:  subscript in assignment must not be null
 UPDATE arrtest
   SET c[NULL:1] = '{"can''t assign"}'
   WHERE array_dims(c) is not null;
-ERROR:  array subscript in assignment must not be null
+ERROR:  subscript in assignment must not be null
 UPDATE arrtest
   SET c[1:NULL] = '{"can''t assign"}'
   WHERE array_dims(c) is not null;
-ERROR:  array subscript in assignment must not be null
+ERROR:  subscript in assignment must not be null
 -- test slices with empty lower and/or upper index
 CREATE TEMP TABLE arrtest_s (
   a       int2[],
diff --git a/src/test/regress/sql/arrays.sql b/src/test/regress/sql/arrays.sql
index 2b689ae88f..afccaf25e1 100644
--- a/src/test/regress/sql/arrays.sql
+++ b/src/test/regress/sql/arrays.sql
@@ -106,8 +106,8 @@ select ('[0:2][0:2]={{1,2,3},{4,5,6},{7,8,9}}'::int[])[1:2][2];
 --
 -- check subscription corner cases
 --
--- More subscripts than MAXDIMS(6)
-SELECT ('{}'::int[])[1][2][3][4][5][6][7];
+-- More subscripts than MAXDIMS(12)
+SELECT ('{}'::int[])[1][2][3][4][5][6][7][8][9][10][11][12][13];
 -- NULL index yields NULL when selecting
 SELECT ('{{{1},{2},{3}},{{4},{5},{6}}}'::int[])[1][NULL][1];
 SELECT ('{{{1},{2},{3}},{{4},{5},{6}}}'::int[])[1][NULL:1][1];
-- 
2.21.0

>From 92adc132d89c2831417ac2e15b37ab9336007733 Mon Sep 17 00:00:00 2001
From: erthalion <9erthali...@gmail.com>
Date: Fri, 1 Feb 2019 11:41:45 +0100
Subject: [PATCH v35 3/5] Subscripting for jsonb

Subscripting implementation for jsonb. For the sake of code reuse, some
parts of jsonb functionality were rearranged to allow use the same
functions for jsonb_set and assign subscripting operation.

Reviewed-by: Tom Lane, Arthur Zakirov
---
 src/backend/utils/adt/jsonb.c       |  27 ++-
 src/backend/utils/adt/jsonb_util.c  |  76 ++++++-
 src/backend/utils/adt/jsonfuncs.c   | 325 ++++++++++++++++++++--------
 src/include/catalog/pg_proc.dat     |   8 +
 src/include/catalog/pg_type.dat     |   3 +-
 src/include/utils/jsonb.h           |   2 +
 src/test/regress/expected/jsonb.out | 233 +++++++++++++++++++-
 src/test/regress/sql/jsonb.sql      |  68 +++++-
 8 files changed, 632 insertions(+), 110 deletions(-)

diff --git a/src/backend/utils/adt/jsonb.c b/src/backend/utils/adt/jsonb.c
index 1e9ca046c6..f66642def3 100644
--- a/src/backend/utils/adt/jsonb.c
+++ b/src/backend/utils/adt/jsonb.c
@@ -1134,23 +1134,34 @@ to_jsonb(PG_FUNCTION_ARGS)
 {
 	Datum		val = PG_GETARG_DATUM(0);
 	Oid			val_type = get_fn_expr_argtype(fcinfo->flinfo, 0);
-	JsonbInState result;
-	JsonbTypeCategory tcategory;
-	Oid			outfuncoid;
+	JsonbValue *res = to_jsonb_worker(val, val_type, false);
+	PG_RETURN_POINTER(JsonbValueToJsonb(res));
+}
 
-	if (val_type == InvalidOid)
+/*
+ * Do the actual conversion to jsonb for to_jsonb function. This logic is
+ * separated because it can be useful not only in here (e.g. we use it in
+ * jsonb subscripting)
+ */
+JsonbValue *
+to_jsonb_worker(Datum source, Oid source_type, bool is_null)
+{
+	JsonbInState		result;
+	JsonbTypeCategory	tcategory;
+	Oid					outfuncoid;
+
+	if (source_type == InvalidOid)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("could not determine input data type")));
 
-	jsonb_categorize_type(val_type,
+	jsonb_categorize_type(source_type,
 						  &tcategory, &outfuncoid);
 
 	memset(&result, 0, sizeof(JsonbInState));
 
-	datum_to_jsonb(val, false, &result, tcategory, outfuncoid, false);
-
-	PG_RETURN_POINTER(JsonbValueToJsonb(result.res));
+	datum_to_jsonb(source, is_null, &result, tcategory, outfuncoid, false);
+	return result.res;
 }
 
 /*
diff --git a/src/backend/utils/adt/jsonb_util.c b/src/backend/utils/adt/jsonb_util.c
index 4eeffa1424..41a1c1f9bb 100644
--- a/src/backend/utils/adt/jsonb_util.c
+++ b/src/backend/utils/adt/jsonb_util.c
@@ -68,18 +68,29 @@ static JsonbValue *pushJsonbValueScalar(JsonbParseState **pstate,
 										JsonbIteratorToken seq,
 										JsonbValue *scalarVal);
 
+JsonbValue *
+JsonbToJsonbValue(Jsonb *jsonb)
+{
+	JsonbValue *val = (JsonbValue *) palloc(sizeof(JsonbValue));
+
+	val->type = jbvBinary;
+	val->val.binary.data = &jsonb->root;
+	val->val.binary.len = VARSIZE(jsonb) - VARHDRSZ;
+
+	return val;
+}
+
 /*
  * Turn an in-memory JsonbValue into a Jsonb for on-disk storage.
  *
- * There isn't a JsonbToJsonbValue(), because generally we find it more
- * convenient to directly iterate through the Jsonb representation and only
- * really convert nested scalar values.  JsonbIteratorNext() does this, so that
- * clients of the iteration code don't have to directly deal with the binary
- * representation (JsonbDeepContains() is a notable exception, although all
- * exceptions are internal to this module).  In general, functions that accept
- * a JsonbValue argument are concerned with the manipulation of scalar values,
- * or simple containers of scalar values, where it would be inconvenient to
- * deal with a great amount of other state.
+ * Generally we find it more convenient to directly iterate through the Jsonb
+ * representation and only really convert nested scalar values.
+ * JsonbIteratorNext() does this, so that clients of the iteration code don't
+ * have to directly deal with the binary representation (JsonbDeepContains() is
+ * a notable exception, although all exceptions are internal to this module).
+ * In general, functions that accept a JsonbValue argument are concerned with
+ * the manipulation of scalar values, or simple containers of scalar values,
+ * where it would be inconvenient to deal with a great amount of other state.
  */
 Jsonb *
 JsonbValueToJsonb(JsonbValue *val)
@@ -563,6 +574,30 @@ pushJsonbValue(JsonbParseState **pstate, JsonbIteratorToken seq,
 	JsonbValue *res = NULL;
 	JsonbValue	v;
 	JsonbIteratorToken tok;
+	int	i;
+
+	if (jbval && (seq == WJB_ELEM || seq == WJB_VALUE) && jbval->type == jbvObject)
+	{
+		pushJsonbValue(pstate, WJB_BEGIN_OBJECT, NULL);
+		for (i = 0; i < jbval->val.object.nPairs; i++)
+		{
+			pushJsonbValue(pstate, WJB_KEY, &jbval->val.object.pairs[i].key);
+			pushJsonbValue(pstate, WJB_VALUE, &jbval->val.object.pairs[i].value);
+		}
+
+		return pushJsonbValue(pstate, WJB_END_OBJECT, NULL);
+	}
+
+	if (jbval && (seq == WJB_ELEM || seq == WJB_VALUE) && jbval->type == jbvArray)
+	{
+		pushJsonbValue(pstate, WJB_BEGIN_ARRAY, NULL);
+		for (i = 0; i < jbval->val.array.nElems; i++)
+		{
+			pushJsonbValue(pstate, WJB_ELEM, &jbval->val.array.elems[i]);
+		}
+
+		return pushJsonbValue(pstate, WJB_END_ARRAY, NULL);
+	}
 
 	if (!jbval || (seq != WJB_ELEM && seq != WJB_VALUE) ||
 		jbval->type != jbvBinary)
@@ -573,9 +608,30 @@ pushJsonbValue(JsonbParseState **pstate, JsonbIteratorToken seq,
 
 	/* unpack the binary and add each piece to the pstate */
 	it = JsonbIteratorInit(jbval->val.binary.data);
+
+	if ((jbval->val.binary.data->header & JB_FSCALAR) && *pstate)
+	{
+		tok = JsonbIteratorNext(&it, &v, true);
+		Assert(tok == WJB_BEGIN_ARRAY);
+		Assert(v.type == jbvArray && v.val.array.rawScalar);
+
+		tok = JsonbIteratorNext(&it, &v, true);
+		Assert(tok == WJB_ELEM);
+
+		res = pushJsonbValueScalar(pstate, seq, &v);
+
+		tok = JsonbIteratorNext(&it, &v, true);
+		Assert(tok == WJB_END_ARRAY);
+		Assert(it == NULL);
+
+		return res;
+	}
+
 	while ((tok = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
 		res = pushJsonbValueScalar(pstate, tok,
-								   tok < WJB_BEGIN_ARRAY ? &v : NULL);
+								   tok < WJB_BEGIN_ARRAY ||
+								   (tok == WJB_BEGIN_ARRAY &&
+									v.val.array.rawScalar) ? &v : NULL);
 
 	return res;
 }
diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index d370348a1c..37508061a1 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -21,12 +21,16 @@
 #include "common/jsonapi.h"
 #include "fmgr.h"
 #include "funcapi.h"
+#include "executor/execExpr.h"
 #include "lib/stringinfo.h"
 #include "mb/pg_wchar.h"
 #include "miscadmin.h"
+#include "nodes/nodeFuncs.h"
+#include "parser/parse_coerce.h"
 #include "utils/array.h"
 #include "utils/builtins.h"
 #include "utils/hsearch.h"
+#include "utils/fmgroids.h"
 #include "utils/json.h"
 #include "utils/jsonb.h"
 #include "utils/jsonfuncs.h"
@@ -460,18 +464,22 @@ static Datum populate_domain(DomainIOData *io, Oid typid, const char *colname,
 /* functions supporting jsonb_delete, jsonb_set and jsonb_concat */
 static JsonbValue *IteratorConcat(JsonbIterator **it1, JsonbIterator **it2,
 								  JsonbParseState **state);
+static Datum jsonb_set_element(Datum datum, Datum *path, int path_len,
+							   Datum sourceData, Oid source_type, bool is_null);
+static Datum jsonb_get_element(Jsonb *jb, Datum *path, int npath,
+							   bool *isnull, bool as_text);
 static JsonbValue *setPath(JsonbIterator **it, Datum *path_elems,
 						   bool *path_nulls, int path_len,
-						   JsonbParseState **st, int level, Jsonb *newval,
+						   JsonbParseState **st, int level, JsonbValue *newval,
 						   int op_type);
 static void setPathObject(JsonbIterator **it, Datum *path_elems,
 						  bool *path_nulls, int path_len, JsonbParseState **st,
 						  int level,
-						  Jsonb *newval, uint32 npairs, int op_type);
+						  JsonbValue *newval, uint32 npairs, int op_type);
 static void setPathArray(JsonbIterator **it, Datum *path_elems,
 						 bool *path_nulls, int path_len, JsonbParseState **st,
-						 int level, Jsonb *newval, uint32 nelems, int op_type);
-static void addJsonbToParseState(JsonbParseState **jbps, Jsonb *jb);
+						 int level,
+						 JsonbValue *newval, uint32 nelems, int op_type);
 
 /* function supporting iterate_json_values */
 static void iterate_values_scalar(void *state, char *token, JsonTokenType tokentype);
@@ -486,6 +494,15 @@ static void transform_string_values_object_field_start(void *state, char *fname,
 static void transform_string_values_array_element_start(void *state, bool isnull);
 static void transform_string_values_scalar(void *state, char *token, JsonTokenType tokentype);
 
+static SubscriptingRef *jsonb_subscript_prepare(bool isAssignment,
+												SubscriptingRef *sbsref);
+
+static SubscriptingRef *jsonb_subscript_validate(bool isAssignment,
+												 SubscriptingRef *sbsref,
+												 ParseState *pstate);
+static Datum jsonb_subscript_fetch(Datum containerSource, SubscriptingRefState *sbstate);
+static Datum jsonb_subscript_assign(Datum containerSource, SubscriptingRefState *sbstate);
+
 /*
  * pg_parse_json_or_ereport
  *
@@ -1447,13 +1464,9 @@ get_jsonb_path_all(FunctionCallInfo fcinfo, bool as_text)
 	ArrayType  *path = PG_GETARG_ARRAYTYPE_P(1);
 	Datum	   *pathtext;
 	bool	   *pathnulls;
+	bool		isnull;
 	int			npath;
-	int			i;
-	bool		have_object = false,
-				have_array = false;
-	JsonbValue *jbvp = NULL;
-	JsonbValue	jbvbuf;
-	JsonbContainer *container;
+	Datum		res;
 
 	/*
 	 * If the array contains any null elements, return NULL, on the grounds
@@ -1468,9 +1481,28 @@ get_jsonb_path_all(FunctionCallInfo fcinfo, bool as_text)
 	deconstruct_array(path, TEXTOID, -1, false, TYPALIGN_INT,
 					  &pathtext, &pathnulls, &npath);
 
-	/* Identify whether we have object, array, or scalar at top-level */
-	container = &jb->root;
+	res = jsonb_get_element(jb, pathtext, npath, &isnull, as_text);
 
+	if (isnull)
+		PG_RETURN_NULL();
+	else
+		PG_RETURN_DATUM(res);
+}
+
+static Datum
+jsonb_get_element(Jsonb *jb, Datum *path, int npath, bool *isnull, bool as_text)
+{
+	Jsonb		   *res;
+	JsonbContainer *container = &jb->root;
+	JsonbValue	   *jbvp = NULL;
+	JsonbValue		tv;
+	int				i;
+	bool			have_object = false,
+					have_array = false;
+
+	*isnull = false;
+
+	/* Identify whether we have object, array, or scalar at top-level */
 	if (JB_ROOT_IS_OBJECT(jb))
 		have_object = true;
 	else if (JB_ROOT_IS_ARRAY(jb) && !JB_ROOT_IS_SCALAR(jb))
@@ -1495,7 +1527,7 @@ get_jsonb_path_all(FunctionCallInfo fcinfo, bool as_text)
 	{
 		if (as_text)
 		{
-			PG_RETURN_TEXT_P(cstring_to_text(JsonbToCString(NULL,
+			return PointerGetDatum(cstring_to_text(JsonbToCString(NULL,
 															container,
 															VARSIZE(jb))));
 		}
@@ -1511,22 +1543,25 @@ get_jsonb_path_all(FunctionCallInfo fcinfo, bool as_text)
 		if (have_object)
 		{
 			jbvp = getKeyJsonValueFromContainer(container,
-												VARDATA(pathtext[i]),
-												VARSIZE(pathtext[i]) - VARHDRSZ,
-												&jbvbuf);
+												VARDATA(path[i]),
+												VARSIZE(path[i]) - VARHDRSZ,
+												NULL);
 		}
 		else if (have_array)
 		{
 			long		lindex;
 			uint32		index;
-			char	   *indextext = TextDatumGetCString(pathtext[i]);
+			char	   *indextext = TextDatumGetCString(path[i]);
 			char	   *endptr;
 
 			errno = 0;
 			lindex = strtol(indextext, &endptr, 10);
 			if (endptr == indextext || *endptr != '\0' || errno != 0 ||
 				lindex > INT_MAX || lindex < INT_MIN)
-				PG_RETURN_NULL();
+			{
+				*isnull = true;
+				return PointerGetDatum(NULL);
+			}
 
 			if (lindex >= 0)
 			{
@@ -1544,7 +1579,10 @@ get_jsonb_path_all(FunctionCallInfo fcinfo, bool as_text)
 				nelements = JsonContainerSize(container);
 
 				if (-lindex > nelements)
-					PG_RETURN_NULL();
+				{
+					*isnull = true;
+					return PointerGetDatum(NULL);
+				}
 				else
 					index = nelements + lindex;
 			}
@@ -1554,11 +1592,15 @@ get_jsonb_path_all(FunctionCallInfo fcinfo, bool as_text)
 		else
 		{
 			/* scalar, extraction yields a null */
-			PG_RETURN_NULL();
+			*isnull = true;
+			return PointerGetDatum(NULL);
 		}
 
 		if (jbvp == NULL)
-			PG_RETURN_NULL();
+		{
+			*isnull = true;
+			return PointerGetDatum(NULL);
+		}
 		else if (i == npath - 1)
 			break;
 
@@ -1580,9 +1622,12 @@ get_jsonb_path_all(FunctionCallInfo fcinfo, bool as_text)
 	if (as_text)
 	{
 		if (jbvp->type == jbvNull)
-			PG_RETURN_NULL();
+		{
+			*isnull = true;
+			return PointerGetDatum(NULL);
+		}
 
-		PG_RETURN_TEXT_P(JsonbValueAsText(jbvp));
+		return PointerGetDatum(JsonbValueAsText(jbvp));
 	}
 	else
 	{
@@ -1593,6 +1638,32 @@ get_jsonb_path_all(FunctionCallInfo fcinfo, bool as_text)
 	}
 }
 
+Datum
+jsonb_set_element(Datum jsonbdatum, Datum *path, int path_len,
+				  Datum sourceData, Oid source_type, bool is_null)
+{
+	Jsonb			   *jb = DatumGetJsonbP(jsonbdatum);
+	JsonbValue		   *newval,
+					   *res;
+	JsonbParseState    *state = NULL;
+	JsonbIterator 	   *it;
+	bool			   *path_nulls = palloc0(path_len * sizeof(bool));
+
+	newval = to_jsonb_worker(sourceData, source_type, is_null);
+
+	if (newval->type == jbvArray && newval->val.array.rawScalar)
+		*newval = newval->val.array.elems[0];
+
+	it = JsonbIteratorInit(&jb->root);
+
+	res = setPath(&it, path, path_nulls, path_len, &state, 0,
+				  newval, JB_PATH_CREATE);
+
+	pfree(path_nulls);
+
+	PG_RETURN_JSONB_P(JsonbValueToJsonb(res));
+}
+
 /*
  * Return the text representation of the given JsonbValue.
  */
@@ -4152,58 +4223,6 @@ jsonb_strip_nulls(PG_FUNCTION_ARGS)
 	PG_RETURN_POINTER(JsonbValueToJsonb(res));
 }
 
-/*
- * Add values from the jsonb to the parse state.
- *
- * If the parse state container is an object, the jsonb is pushed as
- * a value, not a key.
- *
- * This needs to be done using an iterator because pushJsonbValue doesn't
- * like getting jbvBinary values, so we can't just push jb as a whole.
- */
-static void
-addJsonbToParseState(JsonbParseState **jbps, Jsonb *jb)
-{
-	JsonbIterator *it;
-	JsonbValue *o = &(*jbps)->contVal;
-	JsonbValue	v;
-	JsonbIteratorToken type;
-
-	it = JsonbIteratorInit(&jb->root);
-
-	Assert(o->type == jbvArray || o->type == jbvObject);
-
-	if (JB_ROOT_IS_SCALAR(jb))
-	{
-		(void) JsonbIteratorNext(&it, &v, false);	/* skip array header */
-		Assert(v.type == jbvArray);
-		(void) JsonbIteratorNext(&it, &v, false);	/* fetch scalar value */
-
-		switch (o->type)
-		{
-			case jbvArray:
-				(void) pushJsonbValue(jbps, WJB_ELEM, &v);
-				break;
-			case jbvObject:
-				(void) pushJsonbValue(jbps, WJB_VALUE, &v);
-				break;
-			default:
-				elog(ERROR, "unexpected parent of nested structure");
-		}
-	}
-	else
-	{
-		while ((type = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
-		{
-			if (type == WJB_KEY || type == WJB_VALUE || type == WJB_ELEM)
-				(void) pushJsonbValue(jbps, type, &v);
-			else
-				(void) pushJsonbValue(jbps, type, NULL);
-		}
-	}
-
-}
-
 /*
  * SQL function jsonb_pretty (jsonb)
  *
@@ -4475,7 +4494,8 @@ jsonb_set(PG_FUNCTION_ARGS)
 {
 	Jsonb	   *in = PG_GETARG_JSONB_P(0);
 	ArrayType  *path = PG_GETARG_ARRAYTYPE_P(1);
-	Jsonb	   *newval = PG_GETARG_JSONB_P(2);
+	Jsonb	   *newjsonb = PG_GETARG_JSONB_P(2);
+	JsonbValue *newval = JsonbToJsonbValue(newjsonb);
 	bool		create = PG_GETARG_BOOL(3);
 	JsonbValue *res = NULL;
 	Datum	   *path_elems;
@@ -4633,7 +4653,8 @@ jsonb_insert(PG_FUNCTION_ARGS)
 {
 	Jsonb	   *in = PG_GETARG_JSONB_P(0);
 	ArrayType  *path = PG_GETARG_ARRAYTYPE_P(1);
-	Jsonb	   *newval = PG_GETARG_JSONB_P(2);
+	Jsonb	   *newjsonb = PG_GETARG_JSONB_P(2);
+	JsonbValue *newval = JsonbToJsonbValue(newjsonb);
 	bool		after = PG_GETARG_BOOL(3);
 	JsonbValue *res = NULL;
 	Datum	   *path_elems;
@@ -4794,7 +4815,7 @@ IteratorConcat(JsonbIterator **it1, JsonbIterator **it2,
 static JsonbValue *
 setPath(JsonbIterator **it, Datum *path_elems,
 		bool *path_nulls, int path_len,
-		JsonbParseState **st, int level, Jsonb *newval, int op_type)
+		JsonbParseState **st, int level, JsonbValue *newval, int op_type)
 {
 	JsonbValue	v;
 	JsonbIteratorToken r;
@@ -4847,11 +4868,11 @@ setPath(JsonbIterator **it, Datum *path_elems,
 static void
 setPathObject(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 			  int path_len, JsonbParseState **st, int level,
-			  Jsonb *newval, uint32 npairs, int op_type)
+			  JsonbValue *newval, uint32 npairs, int op_type)
 {
-	JsonbValue	v;
 	int			i;
-	JsonbValue	k;
+	JsonbValue	k,
+				v;
 	bool		done = false;
 
 	if (level >= path_len || path_nulls[level])
@@ -4868,7 +4889,7 @@ setPathObject(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 		newkey.val.string.val = VARDATA_ANY(path_elems[level]);
 
 		(void) pushJsonbValue(st, WJB_KEY, &newkey);
-		addJsonbToParseState(st, newval);
+		(void) pushJsonbValue(st, WJB_VALUE, newval);
 	}
 
 	for (i = 0; i < npairs; i++)
@@ -4899,7 +4920,7 @@ setPathObject(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 				if (!(op_type & JB_PATH_DELETE))
 				{
 					(void) pushJsonbValue(st, WJB_KEY, &k);
-					addJsonbToParseState(st, newval);
+					(void) pushJsonbValue(st, WJB_VALUE, newval);
 				}
 				done = true;
 			}
@@ -4922,7 +4943,7 @@ setPathObject(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 				newkey.val.string.val = VARDATA_ANY(path_elems[level]);
 
 				(void) pushJsonbValue(st, WJB_KEY, &newkey);
-				addJsonbToParseState(st, newval);
+				(void) pushJsonbValue(st, WJB_VALUE, newval);
 			}
 
 			(void) pushJsonbValue(st, r, &k);
@@ -4954,7 +4975,7 @@ setPathObject(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 static void
 setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 			 int path_len, JsonbParseState **st, int level,
-			 Jsonb *newval, uint32 nelems, int op_type)
+			 JsonbValue *newval, uint32 nelems, int op_type)
 {
 	JsonbValue	v;
 	int			idx,
@@ -5002,7 +5023,7 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 		(op_type & JB_PATH_CREATE_OR_INSERT))
 	{
 		Assert(newval != NULL);
-		addJsonbToParseState(st, newval);
+		(void) pushJsonbValue(st, WJB_ELEM, newval);
 		done = true;
 	}
 
@@ -5018,7 +5039,7 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 				r = JsonbIteratorNext(it, &v, true);	/* skip */
 
 				if (op_type & (JB_PATH_INSERT_BEFORE | JB_PATH_CREATE))
-					addJsonbToParseState(st, newval);
+					(void) pushJsonbValue(st, WJB_ELEM, newval);
 
 				/*
 				 * We should keep current value only in case of
@@ -5029,7 +5050,7 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 					(void) pushJsonbValue(st, r, &v);
 
 				if (op_type & (JB_PATH_INSERT_AFTER | JB_PATH_REPLACE))
-					addJsonbToParseState(st, newval);
+					(void) pushJsonbValue(st, WJB_ELEM, newval);
 
 				done = true;
 			}
@@ -5063,12 +5084,138 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 			if ((op_type & JB_PATH_CREATE_OR_INSERT) && !done &&
 				level == path_len - 1 && i == nelems - 1)
 			{
-				addJsonbToParseState(st, newval);
+				(void) pushJsonbValue(st, WJB_ELEM, newval);
 			}
 		}
 	}
 }
 
+/*
+ * Perform an actual data extraction or modification for the jsonb
+ * subscripting. As a result the extracted Datum or the modified containers
+ * value will be returned.
+ */
+Datum
+jsonb_subscript_fetch(Datum containerSource, SubscriptingRefState *sbstate)
+{
+	return jsonb_get_element(DatumGetJsonbP(containerSource),
+							 sbstate->upperindex,
+							 sbstate->numupper,
+							 &sbstate->resnull,
+							 false);
+}
+
+
+
+/*
+ * Perform an actual data extraction or modification for the jsonb
+ * subscripting. As a result the extracted Datum or the modified containers
+ * value will be returned.
+ */
+Datum
+jsonb_subscript_assign(Datum containerSource, SubscriptingRefState *sbstate)
+{
+	/*
+	 * the original jsonb must be non-NULL, else we punt and return the
+	 * original array.
+	 */
+	if (sbstate->resnull)
+		return containerSource;
+
+	return jsonb_set_element(containerSource,
+							 sbstate->upperindex,
+							 sbstate->numupper,
+							 sbstate->replacevalue,
+							 sbstate->refelemtype,
+							 sbstate->replacenull);
+}
+
+/*
+ * Perform preparation for the jsonb subscripting. Since there are not any
+ * particular restrictions for this kind of subscripting, we will verify that
+ * it is not a slice operation. This function produces an expression that
+ * represents the result of extracting a single container element or the new
+ * container value with the source data inserted into the right part of the
+ * container. If you have read until this point, and will submit a meaningful
+ * review of this patch series, I'll owe you a beer at the next PGConfEU.
+ */
+
+/*
+ * Handle jsonb-type subscripting logic.
+ */
+Datum
+jsonb_subscript_handler(PG_FUNCTION_ARGS)
+{
+	SubscriptRoutines *sbsroutines = (SubscriptRoutines *)
+									 palloc(sizeof(SubscriptRoutines));
+
+	sbsroutines->prepare = jsonb_subscript_prepare;
+	sbsroutines->validate = jsonb_subscript_validate;
+	sbsroutines->fetch = jsonb_subscript_fetch;
+	sbsroutines->assign = jsonb_subscript_assign;
+
+	PG_RETURN_POINTER(sbsroutines);
+}
+
+SubscriptingRef *
+jsonb_subscript_prepare(bool isAssignment, SubscriptingRef *sbsref)
+{
+	if (isAssignment)
+	{
+		sbsref->refelemtype = exprType((Node *) sbsref->refassgnexpr);
+		sbsref->refassgntype = exprType((Node *) sbsref->refassgnexpr);
+	}
+	else
+		sbsref->refelemtype = JSONBOID;
+
+	return sbsref;
+}
+
+SubscriptingRef *
+jsonb_subscript_validate(bool isAssignment, SubscriptingRef *sbsref,
+						 ParseState *pstate)
+{
+	List			   *upperIndexpr = NIL;
+	ListCell		   *l;
+
+	if (sbsref->reflowerindexpr != NIL)
+		ereport(ERROR,
+				(errcode(ERRCODE_DATATYPE_MISMATCH),
+				 errmsg("jsonb subscript does not support slices"),
+				 parser_errposition(pstate, exprLocation(
+						 ((Node *) linitial(sbsref->reflowerindexpr))))));
+
+	foreach(l, sbsref->refupperindexpr)
+	{
+		Node *subexpr = (Node *) lfirst(l);
+
+		if (subexpr == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+					 errmsg("jsonb subscript does not support slices"),
+					 parser_errposition(pstate, exprLocation(
+						((Node *) linitial(sbsref->refupperindexpr))))));
+
+		subexpr = coerce_to_target_type(pstate,
+										subexpr, exprType(subexpr),
+										TEXTOID, -1,
+										COERCION_ASSIGNMENT,
+										COERCE_IMPLICIT_CAST,
+										-1);
+		if (subexpr == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+					 errmsg("jsonb subscript must have text type"),
+					 parser_errposition(pstate, exprLocation(subexpr))));
+
+		upperIndexpr = lappend(upperIndexpr, subexpr);
+	}
+
+	sbsref->refupperindexpr = upperIndexpr;
+
+	return sbsref;
+}
+
 /*
  * Parse information about what elements of a jsonb document we want to iterate
  * in functions iterate_json(b)_values. This information is presented in jsonb
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 2c6aa65bf8..abcbf97d05 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -10898,6 +10898,14 @@
   proargnames => '{max_data_alignment,database_block_size,blocks_per_segment,wal_block_size,bytes_per_wal_segment,max_identifier_length,max_index_columns,max_toast_chunk_size,large_object_chunk_size,float8_pass_by_value,data_page_checksum_version}',
   prosrc => 'pg_control_init' },
 
+# type subscripting support
+{ oid => '6098',
+  descr => 'Jsonb subscripting logic',
+  proname => 'jsonb_subscript_handler',
+  prorettype => 'internal',
+  proargtypes => 'internal',
+  prosrc => 'jsonb_subscript_handler' },
+
 { oid => '6099',
   descr => 'Array subscripting logic',
   proname => 'array_subscript_handler',
diff --git a/src/include/catalog/pg_type.dat b/src/include/catalog/pg_type.dat
index 21489a02ae..fa7e1d22a5 100644
--- a/src/include/catalog/pg_type.dat
+++ b/src/include/catalog/pg_type.dat
@@ -456,7 +456,8 @@
 { oid => '3802', array_type_oid => '3807', descr => 'Binary JSON',
   typname => 'jsonb', typlen => '-1', typbyval => 'f', typcategory => 'U',
   typinput => 'jsonb_in', typoutput => 'jsonb_out', typreceive => 'jsonb_recv',
-  typsend => 'jsonb_send', typalign => 'i', typstorage => 'x' },
+  typsend => 'jsonb_send', typalign => 'i', typstorage => 'x',
+  typsubshandler => 'jsonb_subscript_handler' },
 { oid => '4072', array_type_oid => '4073', descr => 'JSON path',
   typname => 'jsonpath', typlen => '-1', typbyval => 'f', typcategory => 'U',
   typinput => 'jsonpath_in', typoutput => 'jsonpath_out',
diff --git a/src/include/utils/jsonb.h b/src/include/utils/jsonb.h
index 5860011693..6e3b75d56a 100644
--- a/src/include/utils/jsonb.h
+++ b/src/include/utils/jsonb.h
@@ -392,6 +392,7 @@ extern JsonbValue *pushJsonbValue(JsonbParseState **pstate,
 extern JsonbIterator *JsonbIteratorInit(JsonbContainer *container);
 extern JsonbIteratorToken JsonbIteratorNext(JsonbIterator **it, JsonbValue *val,
 											bool skipNested);
+extern JsonbValue *JsonbToJsonbValue(Jsonb *jsonb);
 extern Jsonb *JsonbValueToJsonb(JsonbValue *val);
 extern bool JsonbDeepContains(JsonbIterator **val,
 							  JsonbIterator **mContained);
@@ -407,5 +408,6 @@ extern char *JsonbToCStringIndent(StringInfo out, JsonbContainer *in,
 extern bool JsonbExtractScalar(JsonbContainer *jbc, JsonbValue *res);
 extern const char *JsonbTypeName(JsonbValue *jb);
 
+extern JsonbValue *to_jsonb_worker(Datum source, Oid source_type, bool is_null);
 
 #endif							/* __JSONB_H__ */
diff --git a/src/test/regress/expected/jsonb.out b/src/test/regress/expected/jsonb.out
index a70cd0b7c1..04a146a7d0 100644
--- a/src/test/regress/expected/jsonb.out
+++ b/src/test/regress/expected/jsonb.out
@@ -4567,7 +4567,7 @@ select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment => 'use_
  {"a": 1, "b": null}
 (1 row)
 
-\pset null
+\pset null ''
 -- jsonb_insert
 select jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"');
          jsonb_insert          
@@ -4697,6 +4697,237 @@ HINT:  Try using the function jsonb_set to replace key value.
 select jsonb_insert('{"a": {"b": "value"}}', '{a, b}', '"new_value"', true);
 ERROR:  cannot replace existing key
 HINT:  Try using the function jsonb_set to replace key value.
+-- jsonb subscript
+select ('123'::jsonb)['a'];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('123'::jsonb)[0];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('123'::jsonb)[NULL];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('{"a": 1}'::jsonb)['a'];
+ jsonb 
+-------
+ 1
+(1 row)
+
+select ('{"a": 1}'::jsonb)[0];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('{"a": 1}'::jsonb)['not_exist'];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('{"a": 1}'::jsonb)[NULL];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('[1, "2", null]'::jsonb)['a'];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('[1, "2", null]'::jsonb)[0];
+ jsonb 
+-------
+ 1
+(1 row)
+
+select ('[1, "2", null]'::jsonb)['1'];
+ jsonb 
+-------
+ "2"
+(1 row)
+
+select ('[1, "2", null]'::jsonb)[1.0];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('[1, "2", null]'::jsonb)[2];
+ jsonb 
+-------
+ null
+(1 row)
+
+select ('[1, "2", null]'::jsonb)[3];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('[1, "2", null]'::jsonb)[-2];
+ jsonb 
+-------
+ "2"
+(1 row)
+
+select ('[1, "2", null]'::jsonb)[1]['a'];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('[1, "2", null]'::jsonb)[1][0];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['b'];
+ jsonb 
+-------
+ "c"
+(1 row)
+
+select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['d'];
+   jsonb   
+-----------
+ [1, 2, 3]
+(1 row)
+
+select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['d'][1];
+ jsonb 
+-------
+ 2
+(1 row)
+
+select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['d']['a'];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('{"a": {"a1": {"a2": "aaa"}}, "b": "bbb", "c": "ccc"}'::jsonb)['a']['a1'];
+     jsonb     
+---------------
+ {"a2": "aaa"}
+(1 row)
+
+select ('{"a": {"a1": {"a2": "aaa"}}, "b": "bbb", "c": "ccc"}'::jsonb)['a']['a1']['a2'];
+ jsonb 
+-------
+ "aaa"
+(1 row)
+
+select ('{"a": {"a1": {"a2": "aaa"}}, "b": "bbb", "c": "ccc"}'::jsonb)['a']['a1']['a2']['a3'];
+ jsonb 
+-------
+ 
+(1 row)
+
+select ('{"a": ["a1", {"b1": ["aaa", "bbb", "ccc"]}], "b": "bb"}'::jsonb)['a'][1]['b1'];
+         jsonb         
+-----------------------
+ ["aaa", "bbb", "ccc"]
+(1 row)
+
+select ('{"a": ["a1", {"b1": ["aaa", "bbb", "ccc"]}], "b": "bb"}'::jsonb)['a'][1]['b1'][2];
+ jsonb 
+-------
+ "ccc"
+(1 row)
+
+create TEMP TABLE test_jsonb_subscript (
+       id int,
+       test_json jsonb
+);
+insert into test_jsonb_subscript values
+(1, '{}'), -- empty jsonb
+(2, '{"key": "value"}'); -- jsonb with data
+-- update empty jsonb
+update test_jsonb_subscript set test_json['a'] = 1 where id = 1;
+select * from test_jsonb_subscript;
+ id |    test_json     
+----+------------------
+  2 | {"key": "value"}
+  1 | {"a": 1}
+(2 rows)
+
+-- update jsonb with some data
+update test_jsonb_subscript set test_json['a'] = 1 where id = 2;
+select * from test_jsonb_subscript;
+ id |        test_json         
+----+--------------------------
+  1 | {"a": 1}
+  2 | {"a": 1, "key": "value"}
+(2 rows)
+
+-- replace jsonb
+update test_jsonb_subscript set test_json['a'] = 'test';
+select * from test_jsonb_subscript;
+ id |           test_json           
+----+-------------------------------
+  1 | {"a": "test"}
+  2 | {"a": "test", "key": "value"}
+(2 rows)
+
+-- replace by object
+update test_jsonb_subscript set test_json['a'] = '{"b": 1}'::jsonb;
+select * from test_jsonb_subscript;
+ id |            test_json            
+----+---------------------------------
+  1 | {"a": {"b": 1}}
+  2 | {"a": {"b": 1}, "key": "value"}
+(2 rows)
+
+-- replace by array
+update test_jsonb_subscript set test_json['a'] = '[1, 2, 3]'::jsonb;
+select * from test_jsonb_subscript;
+ id |            test_json             
+----+----------------------------------
+  1 | {"a": [1, 2, 3]}
+  2 | {"a": [1, 2, 3], "key": "value"}
+(2 rows)
+
+-- use jsonb subscription in where clause
+select * from test_jsonb_subscript where test_json['key'] = '"value"';
+ id |            test_json             
+----+----------------------------------
+  2 | {"a": [1, 2, 3], "key": "value"}
+(1 row)
+
+select * from test_jsonb_subscript where test_json['key_doesnt_exists'] = '"value"';
+ id | test_json 
+----+-----------
+(0 rows)
+
+select * from test_jsonb_subscript where test_json['key'] = '"wrong_value"';
+ id | test_json 
+----+-----------
+(0 rows)
+
+-- NULL
+update test_jsonb_subscript set test_json[NULL] = 1;
+ERROR:  subscript in assignment must not be null
+update test_jsonb_subscript set test_json['another_key'] = NULL;
+select * from test_jsonb_subscript;
+ id |                       test_json                       
+----+-------------------------------------------------------
+  1 | {"a": [1, 2, 3], "another_key": null}
+  2 | {"a": [1, 2, 3], "key": "value", "another_key": null}
+(2 rows)
+
 -- jsonb to tsvector
 select to_tsvector('{"a": "aaa bbb ddd ccc", "b": ["eee fff ggg"], "c": {"d": "hhh iii"}}'::jsonb);
                                 to_tsvector                                
diff --git a/src/test/regress/sql/jsonb.sql b/src/test/regress/sql/jsonb.sql
index 3e2b8f66df..12541e7e50 100644
--- a/src/test/regress/sql/jsonb.sql
+++ b/src/test/regress/sql/jsonb.sql
@@ -1172,7 +1172,7 @@ select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment => 'retu
 select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment => 'delete_key') as delete_key;
 select jsonb_set_lax('{"a":1,"b":2}', '{b}', null, null_value_treatment => 'use_json_null') as use_json_null;
 
-\pset null
+\pset null ''
 
 -- jsonb_insert
 select jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"');
@@ -1203,6 +1203,72 @@ select jsonb_insert('{"a": {"b": "value"}}', '{a, c}', '"new_value"', true);
 select jsonb_insert('{"a": {"b": "value"}}', '{a, b}', '"new_value"');
 select jsonb_insert('{"a": {"b": "value"}}', '{a, b}', '"new_value"', true);
 
+-- jsonb subscript
+select ('123'::jsonb)['a'];
+select ('123'::jsonb)[0];
+select ('123'::jsonb)[NULL];
+select ('{"a": 1}'::jsonb)['a'];
+select ('{"a": 1}'::jsonb)[0];
+select ('{"a": 1}'::jsonb)['not_exist'];
+select ('{"a": 1}'::jsonb)[NULL];
+select ('[1, "2", null]'::jsonb)['a'];
+select ('[1, "2", null]'::jsonb)[0];
+select ('[1, "2", null]'::jsonb)['1'];
+select ('[1, "2", null]'::jsonb)[1.0];
+select ('[1, "2", null]'::jsonb)[2];
+select ('[1, "2", null]'::jsonb)[3];
+select ('[1, "2", null]'::jsonb)[-2];
+select ('[1, "2", null]'::jsonb)[1]['a'];
+select ('[1, "2", null]'::jsonb)[1][0];
+select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['b'];
+select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['d'];
+select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['d'][1];
+select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['d']['a'];
+select ('{"a": {"a1": {"a2": "aaa"}}, "b": "bbb", "c": "ccc"}'::jsonb)['a']['a1'];
+select ('{"a": {"a1": {"a2": "aaa"}}, "b": "bbb", "c": "ccc"}'::jsonb)['a']['a1']['a2'];
+select ('{"a": {"a1": {"a2": "aaa"}}, "b": "bbb", "c": "ccc"}'::jsonb)['a']['a1']['a2']['a3'];
+select ('{"a": ["a1", {"b1": ["aaa", "bbb", "ccc"]}], "b": "bb"}'::jsonb)['a'][1]['b1'];
+select ('{"a": ["a1", {"b1": ["aaa", "bbb", "ccc"]}], "b": "bb"}'::jsonb)['a'][1]['b1'][2];
+
+create TEMP TABLE test_jsonb_subscript (
+       id int,
+       test_json jsonb
+);
+
+insert into test_jsonb_subscript values
+(1, '{}'), -- empty jsonb
+(2, '{"key": "value"}'); -- jsonb with data
+
+-- update empty jsonb
+update test_jsonb_subscript set test_json['a'] = 1 where id = 1;
+select * from test_jsonb_subscript;
+
+-- update jsonb with some data
+update test_jsonb_subscript set test_json['a'] = 1 where id = 2;
+select * from test_jsonb_subscript;
+
+-- replace jsonb
+update test_jsonb_subscript set test_json['a'] = 'test';
+select * from test_jsonb_subscript;
+
+-- replace by object
+update test_jsonb_subscript set test_json['a'] = '{"b": 1}'::jsonb;
+select * from test_jsonb_subscript;
+
+-- replace by array
+update test_jsonb_subscript set test_json['a'] = '[1, 2, 3]'::jsonb;
+select * from test_jsonb_subscript;
+
+-- use jsonb subscription in where clause
+select * from test_jsonb_subscript where test_json['key'] = '"value"';
+select * from test_jsonb_subscript where test_json['key_doesnt_exists'] = '"value"';
+select * from test_jsonb_subscript where test_json['key'] = '"wrong_value"';
+
+-- NULL
+update test_jsonb_subscript set test_json[NULL] = 1;
+update test_jsonb_subscript set test_json['another_key'] = NULL;
+select * from test_jsonb_subscript;
+
 -- jsonb to tsvector
 select to_tsvector('{"a": "aaa bbb ddd ccc", "b": ["eee fff ggg"], "c": {"d": "hhh iii"}}'::jsonb);
 
-- 
2.21.0

>From f3311545a7c6b7f06fde2ce242b2cb3913fa3164 Mon Sep 17 00:00:00 2001
From: erthalion <9erthali...@gmail.com>
Date: Fri, 1 Feb 2019 11:47:37 +0100
Subject: [PATCH v35 4/5] Subscripting documentation

Supporting documentation for generalized subscripting. It includes the
description of a new field in pg_type, the new section for jsonb
documentation about subscripting feature on this data type, and also the
tutorial about how to write subscripting operator for a custom data type.

Reviewed-by: Tom Lane, Arthur Zakirov, Oleksandr Shulgin
---
 doc/src/sgml/catalogs.sgml        |   8 ++
 doc/src/sgml/extend.sgml          |   6 +
 doc/src/sgml/filelist.sgml        |   1 +
 doc/src/sgml/json.sgml            |  39 ++++++
 doc/src/sgml/ref/create_type.sgml |  33 ++++-
 doc/src/sgml/xsubscripting.sgml   | 113 +++++++++++++++++
 src/tutorial/Makefile             |   4 +-
 src/tutorial/subscripting.c       | 204 ++++++++++++++++++++++++++++++
 src/tutorial/subscripting.source  |  71 +++++++++++
 9 files changed, 475 insertions(+), 4 deletions(-)
 create mode 100644 doc/src/sgml/xsubscripting.sgml
 create mode 100644 src/tutorial/subscripting.c
 create mode 100644 src/tutorial/subscripting.source

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 7e99928d0c..104cea3584 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -8990,6 +8990,14 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry><structfield>typsubshandler</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>Custom subscripting function with type-specific logic for parsing
+      and validation, or 0 if this type doesn't support subscripting.</entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>typdefault</structfield> <type>text</type>
diff --git a/doc/src/sgml/extend.sgml b/doc/src/sgml/extend.sgml
index e486006224..23c1764571 100644
--- a/doc/src/sgml/extend.sgml
+++ b/doc/src/sgml/extend.sgml
@@ -33,6 +33,11 @@
       operators (starting in <xref linkend="xoper"/>)
      </para>
     </listitem>
+    <listitem>
+     <para>
+      subscripting procedure (starting in <xref linkend="xsubscripting"/>)
+     </para>
+    </listitem>
     <listitem>
      <para>
       operator classes for indexes (starting in <xref linkend="xindex"/>)
@@ -481,6 +486,7 @@ RETURNS anycompatible AS ...
   &xaggr;
   &xtypes;
   &xoper;
+  &xsubscripting;
   &xindex;
 
 
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml
index 828396d4a9..3bebb34c1a 100644
--- a/doc/src/sgml/filelist.sgml
+++ b/doc/src/sgml/filelist.sgml
@@ -69,6 +69,7 @@
 <!ENTITY xplang     SYSTEM "xplang.sgml">
 <!ENTITY xoper      SYSTEM "xoper.sgml">
 <!ENTITY xtypes     SYSTEM "xtypes.sgml">
+<!ENTITY xsubscripting SYSTEM "xsubscripting.sgml">
 <!ENTITY plperl     SYSTEM "plperl.sgml">
 <!ENTITY plpython   SYSTEM "plpython.sgml">
 <!ENTITY plsql      SYSTEM "plpgsql.sgml">
diff --git a/doc/src/sgml/json.sgml b/doc/src/sgml/json.sgml
index c0a6554d4d..5c538dca05 100644
--- a/doc/src/sgml/json.sgml
+++ b/doc/src/sgml/json.sgml
@@ -602,6 +602,45 @@ SELECT jdoc-&gt;'guid', jdoc-&gt;'name' FROM api WHERE jdoc @&gt; '{"tags": ["qu
   </para>
  </sect2>
 
+ <sect2 id="jsonb-subscripting">
+  <title><type>jsonb</type> Subscripting</title>
+  <para>
+   <type>jsonb</type> data type supports array-style subscripting expressions
+   to extract or update particular elements. It's possible to use multiple
+   subscripting expressions to extract nested values. In this case, a chain of
+   subscripting expressions follows the same rules as the
+   <literal>path</literal> argument in <literal>jsonb_set</literal> function,
+   e.g. in case of arrays it is a 0-based operation or that negative integers
+   that appear in <literal>path</literal> count from the end of JSON arrays.
+   The result of subscripting expressions is always jsonb data type. An
+   example of subscripting syntax:
+<programlisting>
+-- Extract value by key
+SELECT ('{"a": 1}'::jsonb)['a'];
+
+-- Extract nested value by key path
+SELECT ('{"a": {"b": {"c": 1}}}'::jsonb)['a']['b']['c'];
+
+-- Extract element by index
+SELECT ('[1, "2", null]'::jsonb)[1];
+
+-- Update value by key
+UPDATE table_name SET jsonb_field['key'] = 1;
+
+-- Select records using where clause with subscripting. Since the result of
+-- subscripting is jsonb and we basically want to compare two jsonb objects, we
+-- need to put the value in double quotes to be able to convert it to jsonb.
+SELECT * FROM table_name WHERE jsonb_field['key'] = '"value"';
+</programlisting>
+
+  There is no special indexing support for such kind of expressions, but you
+  can always create a functional index that includes it
+<programlisting>
+CREATE INDEX idx ON table_name ((jsonb_field['key']));
+</programlisting>
+  </para>
+ </sect2>
+
  <sect2>
   <title>Transforms</title>
 
diff --git a/doc/src/sgml/ref/create_type.sgml b/doc/src/sgml/ref/create_type.sgml
index 111f8e65d2..a34df4d247 100644
--- a/doc/src/sgml/ref/create_type.sgml
+++ b/doc/src/sgml/ref/create_type.sgml
@@ -54,6 +54,7 @@ CREATE TYPE <replaceable class="parameter">name</replaceable> (
     [ , ELEMENT = <replaceable class="parameter">element</replaceable> ]
     [ , DELIMITER = <replaceable class="parameter">delimiter</replaceable> ]
     [ , COLLATABLE = <replaceable class="parameter">collatable</replaceable> ]
+    [ , SUBSCRIPTING_HANDLER = <replaceable class="parameter">subscripting_handler_function</replaceable> ]
 )
 
 CREATE TYPE <replaceable class="parameter">name</replaceable>
@@ -196,8 +197,9 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
    <replaceable class="parameter">receive_function</replaceable>,
    <replaceable class="parameter">send_function</replaceable>,
    <replaceable class="parameter">type_modifier_input_function</replaceable>,
-   <replaceable class="parameter">type_modifier_output_function</replaceable> and
-   <replaceable class="parameter">analyze_function</replaceable>
+   <replaceable class="parameter">type_modifier_output_function</replaceable>,
+   <replaceable class="parameter">analyze_function</replaceable>,
+   <replaceable class="parameter">subscripting_handler_function</replaceable>
    are optional.  Generally these functions have to be coded in C
    or another low-level language.
   </para>
@@ -454,6 +456,22 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
    make use of the collation information; this does not happen
    automatically merely by marking the type collatable.
   </para>
+
+  <para>
+   The optional
+   <replaceable class="parameter">subscripting_handler_function</replaceable>
+   contains type-specific logic for subscripting of the data type.
+   By default, there is no such function provided, which means that the data
+   type doesn't support subscripting. The subscripting function must be
+   declared to take a single argument of type <type>internal</type>, and return
+   a <type>internal</type> result. There are two examples of implementation for
+   subscripting functions in case of array
+   (<replaceable class="parameter">array_subscripting_handler</replaceable>)
+   and jsonb
+   (<replaceable class="parameter">jsonb_subscripting_handler</replaceable>)
+   types in <filename>src/backend/utils/adt/arrayfuncs.c</filename> and
+   <filename>src/backend/utils/adt/jsonfuncs.c</filename>, respectively.
+  </para>
   </refsect2>
 
   <refsect2>
@@ -769,6 +787,17 @@ CREATE TYPE <replaceable class="parameter">name</replaceable>
      </para>
     </listitem>
    </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">subscripting_handler_function</replaceable></term>
+    <listitem>
+     <para>
+      The name of a function that returns list of type-specific callback functions to
+      support subscripting logic for the data type.
+     </para>
+    </listitem>
+   </varlistentry>
+
   </variablelist>
  </refsect1>
 
diff --git a/doc/src/sgml/xsubscripting.sgml b/doc/src/sgml/xsubscripting.sgml
new file mode 100644
index 0000000000..5282df0361
--- /dev/null
+++ b/doc/src/sgml/xsubscripting.sgml
@@ -0,0 +1,113 @@
+<!-- doc/src/sgml/xsubscripting.sgml -->
+
+ <sect1 id="xsubscripting">
+  <title>User-defined subscripting procedure</title>
+
+  <indexterm zone="xsubscripting">
+    <primary>custom subscripting</primary>
+  </indexterm>
+  <para>
+  When you define a new base type, you can also specify a custom procedure to
+  handle subscripting expressions. It must contain logic for verification and
+  evaluation of this expression, i.e. fetching or updating some data in this
+  data type. For instance:
+</para>
+<programlisting><![CDATA[
+typedef struct Custom
+{
+    int first;
+    int second;
+}   Custom;
+
+PG_FUNCTION_INFO_V1(custom_subscripting_handler);
+
+Datum
+custom_subscripting_handler(PG_FUNCTION_ARGS)
+{
+    SubscriptRoutines *sbsroutines = (SubscriptRoutines *)
+                                     palloc(sizeof(SubscriptRoutines));
+    sbsroutines->prepare = custom_subscript_prepare;
+    sbsroutines->validate = custom_subscript_validate;
+    sbsroutines->fetch = custom_subscript_fetch;
+    sbsroutines->assign = custom_subscript_assign;
+
+    PG_RETURN_POINTER(sbsroutines);
+}
+
+SubscriptingRef *
+custom_subscript_prepare(bool isAssignment, SubscriptingRef *sbsref)
+{
+    sbsref->refelemtype = someType;
+    sbsref->refassgntype = someType;
+
+    // You can also store any necessary information into sbsref->refopaque
+
+    return sbsref;
+}
+
+SubscriptingRef *
+custom_subscript_validate(bool isAssignment, SubscriptingRef *sbsref,
+                          ParseState *pstate)
+{
+    // some validation and coercion logic
+
+    return sbsref;
+}
+
+Datum
+custom_subscript_assign(Datum containerSource, SubscriptingRefState *sbstate)
+{
+    // Some assignment logic
+
+    return newContainer;
+}
+
+Datum
+custom_subscript_fetch(Datum containerSource, SubscriptingRefState *sbstate)
+{
+    // Some fetch logic based on sbstate
+}]]>
+</programlisting>
+
+<para>
+    Then you can define a subscripting procedure and a custom data type:
+</para>
+<programlisting>
+CREATE FUNCTION custom_subscripting_handler(internal)
+    RETURNS internal
+    AS '<replaceable>filename</replaceable>'
+    LANGUAGE C IMMUTABLE STRICT;
+
+CREATE TYPE custom (
+   internallength = 4,
+   input = custom_in,
+   output = custom_out,
+   subscripting_handler = custom_subscripting_handler,
+);
+</programlisting>
+
+<para>
+    and use it as usual:
+</para>
+<programlisting>
+CREATE TABLE test_subscripting (
+    data    custom
+);
+
+INSERT INTO test_subscripting VALUES ('(1, 2)');
+
+SELECT data[0] from test_subscripting;
+
+UPDATE test_subscripting SET data[1] = 3;
+</programlisting>
+
+
+  <para>
+   The examples of custom subscripting implementation can be found in
+   <filename>subscripting.sql</filename> and <filename>subscripting.c</filename>
+   in the <filename>src/tutorial</filename> directory of the source distribution.
+   See the <filename>README</filename> file in that directory for instructions
+   about running the examples.
+  </para>
+
+</sect1>
diff --git a/src/tutorial/Makefile b/src/tutorial/Makefile
index 16dc390f71..0ead60c2d4 100644
--- a/src/tutorial/Makefile
+++ b/src/tutorial/Makefile
@@ -13,8 +13,8 @@
 #
 #-------------------------------------------------------------------------
 
-MODULES = complex funcs
-DATA_built = advanced.sql basics.sql complex.sql funcs.sql syscat.sql
+MODULES = complex funcs subscripting
+DATA_built = advanced.sql basics.sql complex.sql funcs.sql syscat.sql subscripting.sql
 
 ifdef NO_PGXS
 subdir = src/tutorial
diff --git a/src/tutorial/subscripting.c b/src/tutorial/subscripting.c
new file mode 100644
index 0000000000..aaac7927c6
--- /dev/null
+++ b/src/tutorial/subscripting.c
@@ -0,0 +1,204 @@
+/*
+ * src/tutorial/subscripting.c
+ *
+ ******************************************************************************
+  This file contains routines that can be bound to a Postgres backend and
+  called by the backend in the process of processing queries.  The calling
+  format for these routines is dictated by Postgres architecture.
+******************************************************************************/
+
+#include "postgres.h"
+
+#include "catalog/pg_type.h"
+#include "executor/executor.h"
+#include "executor/execExpr.h"
+#include "nodes/nodeFuncs.h"
+#include "parser/parse_coerce.h"
+#include "utils/builtins.h"
+#include "utils/fmgrprotos.h"
+
+PG_MODULE_MAGIC;
+
+typedef struct Custom
+{
+	int	first;
+	int	second;
+}	Custom;
+
+SubscriptingRef * custom_subscript_prepare(bool isAssignment, SubscriptingRef *sbsref);
+SubscriptingRef * custom_subscript_validate(bool isAssignment, SubscriptingRef *sbsref,
+											ParseState *pstate);
+Datum custom_subscript_fetch(Datum containerSource, SubscriptingRefState *sbstate);
+Datum custom_subscript_assign(Datum containerSource, SubscriptingRefState *sbstate);
+
+PG_FUNCTION_INFO_V1(custom_in);
+PG_FUNCTION_INFO_V1(custom_out);
+PG_FUNCTION_INFO_V1(custom_subscripting_handler);
+
+/*****************************************************************************
+ * Input/Output functions
+ *****************************************************************************/
+
+Datum
+custom_in(PG_FUNCTION_ARGS)
+{
+	char	*str = PG_GETARG_CSTRING(0);
+	int		firstValue,
+			secondValue;
+	Custom	*result;
+
+	if (sscanf(str, " ( %d , %d )", &firstValue, &secondValue) != 2)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+				 errmsg("invalid input syntax for complex: \"%s\"",
+						str)));
+
+
+	result = (Custom *) palloc(sizeof(Custom));
+	result->first = firstValue;
+	result->second = secondValue;
+	PG_RETURN_POINTER(result);
+}
+
+Datum
+custom_out(PG_FUNCTION_ARGS)
+{
+	Custom	*custom = (Custom *) PG_GETARG_POINTER(0);
+	char	*result;
+
+	result = psprintf("(%d, %d)", custom->first, custom->second);
+	PG_RETURN_CSTRING(result);
+}
+
+/*****************************************************************************
+ * Custom subscripting logic functions
+ *****************************************************************************/
+
+Datum
+custom_subscripting_handler(PG_FUNCTION_ARGS)
+{
+	SubscriptRoutines *sbsroutines = (SubscriptRoutines *)
+									 palloc(sizeof(SubscriptRoutines));
+
+	sbsroutines->prepare = custom_subscript_prepare;
+	sbsroutines->validate = custom_subscript_validate;
+	sbsroutines->fetch = custom_subscript_fetch;
+	sbsroutines->assign = custom_subscript_assign;
+
+	PG_RETURN_POINTER(sbsroutines);
+}
+
+SubscriptingRef *
+custom_subscript_prepare(bool isAssignment, SubscriptingRef *sbsref)
+{
+	sbsref->refelemtype = INT4OID;
+	sbsref->refassgntype = INT4OID;
+
+	/* You can also store any necessary information into sbsref->refopaque */
+
+	return sbsref;
+}
+
+SubscriptingRef *
+custom_subscript_validate(bool isAssignment, SubscriptingRef *sbsref,
+						  ParseState *pstate)
+{
+	List			   *upperIndexpr = NIL;
+	ListCell		   *l;
+
+	if (sbsref->reflowerindexpr != NIL)
+		ereport(ERROR,
+				(errcode(ERRCODE_DATATYPE_MISMATCH),
+				 errmsg("custom subscript does not support slices"),
+				 parser_errposition(pstate, exprLocation(
+						 ((Node *)lfirst(sbsref->reflowerindexpr->head))))));
+
+	foreach(l, sbsref->refupperindexpr)
+	{
+		Node *subexpr = (Node *) lfirst(l);
+
+		if (subexpr == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+					 errmsg("custom subscript does not support slices"),
+					 parser_errposition(pstate, exprLocation(
+						((Node *) lfirst(sbsref->refupperindexpr->head))))));
+
+		subexpr = coerce_to_target_type(pstate,
+										subexpr, exprType(subexpr),
+										INT4OID, -1,
+										COERCION_ASSIGNMENT,
+										COERCE_IMPLICIT_CAST,
+										-1);
+		if (subexpr == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_DATATYPE_MISMATCH),
+					 errmsg("custom subscript must have integer type"),
+					 parser_errposition(pstate, exprLocation(subexpr))));
+
+		upperIndexpr = lappend(upperIndexpr, subexpr);
+
+		if (isAssignment)
+		{
+			Node *assignExpr = (Node *) sbsref->refassgnexpr;
+			Node *new_from;
+
+			new_from = coerce_to_target_type(pstate,
+					assignExpr, exprType(assignExpr),
+					INT4OID, -1,
+					COERCION_ASSIGNMENT,
+					COERCE_IMPLICIT_CAST,
+					-1);
+			if (new_from == NULL)
+				ereport(ERROR,
+						(errcode(ERRCODE_DATATYPE_MISMATCH),
+						 errmsg("custom assignment requires int type"),
+						 errhint("You will need to rewrite or cast the expression."),
+						 parser_errposition(pstate, exprLocation(assignExpr))));
+			sbsref->refassgnexpr = (Expr *)new_from;
+		}
+	}
+
+	sbsref->refupperindexpr = upperIndexpr;
+
+	return sbsref;
+}
+
+Datum
+custom_subscript_fetch(Datum containerSource, SubscriptingRefState *sbstate)
+{
+	Custom	*container= (Custom *) containerSource;
+	int		 index;
+
+	if (sbstate->numupper != 1)
+		ereport(ERROR, (errmsg("custom does not support nested subscripting")));
+
+	index = DatumGetInt32(sbstate->upperindex[0]);
+
+	if (index == 1)
+		return (Datum) container->first;
+	else
+		return (Datum) container->second;
+}
+
+Datum
+custom_subscript_assign(Datum containerSource, SubscriptingRefState *sbstate)
+{
+	int	index;
+	Custom *container = (Custom *) containerSource;
+
+	if (sbstate->resnull)
+		return containerSource;
+
+	if (sbstate->numupper != 1)
+		ereport(ERROR, (errmsg("custom does not support nested subscripting")));
+
+	index = DatumGetInt32(sbstate->upperindex[0]);
+
+	if (index == 1)
+		container->first = DatumGetInt32(sbstate->replacevalue);
+	else
+		container->second = DatumGetInt32(sbstate->replacevalue);
+
+	return (Datum) container;
+}
diff --git a/src/tutorial/subscripting.source b/src/tutorial/subscripting.source
new file mode 100644
index 0000000000..837cf30612
--- /dev/null
+++ b/src/tutorial/subscripting.source
@@ -0,0 +1,71 @@
+---------------------------------------------------------------------------
+--
+-- subscripting.sql-
+--    This file shows how to create a new subscripting procedure for
+--    user-defined type.
+--
+--
+-- Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
+-- Portions Copyright (c) 1994, Regents of the University of California
+--
+-- src/tutorial/subscripting.source
+--
+---------------------------------------------------------------------------
+
+-----------------------------
+-- Creating a new type:
+--	We are going to create a new type called 'complex' which represents
+--	complex numbers.
+--	A user-defined type must have an input and an output function, and
+--	optionally can have binary input and output functions.  All of these
+--	are usually user-defined C functions.
+-----------------------------
+
+-- Assume the user defined functions are in /home/erthalion/programms/postgresql-master/src/tutorial/complex$DLSUFFIX
+-- (we do not want to assume this is in the dynamic loader search path).
+-- Look at $PWD/complex.c for the source.  Note that we declare all of
+-- them as STRICT, so we do not need to cope with NULL inputs in the
+-- C code.  We also mark them IMMUTABLE, since they always return the
+-- same outputs given the same inputs.
+
+-- the input function 'complex_in' takes a null-terminated string (the
+-- textual representation of the type) and turns it into the internal
+-- (in memory) representation. You will get a message telling you 'complex'
+-- does not exist yet but that's okay.
+
+CREATE FUNCTION custom_in(cstring)
+   RETURNS custom
+   AS '_OBJWD_/subscripting'
+   LANGUAGE C IMMUTABLE STRICT;
+
+-- the output function 'complex_out' takes the internal representation and
+-- converts it into the textual representation.
+
+CREATE FUNCTION custom_out(custom)
+   RETURNS cstring
+   AS '_OBJWD_/subscripting'
+   LANGUAGE C IMMUTABLE STRICT;
+
+CREATE FUNCTION custom_subscripting_handler(internal)
+   RETURNS internal
+   AS '_OBJWD_/subscripting'
+   LANGUAGE C IMMUTABLE STRICT;
+
+CREATE TYPE custom (
+   internallength = 8,
+   input = custom_in,
+   output = custom_out,
+   subscripting_handler = custom_subscripting_handler
+);
+
+-- we can use it in a table
+
+CREATE TABLE test_subscripting (
+	data	custom
+);
+
+INSERT INTO test_subscripting VALUES ('(1, 2)');
+
+SELECT data[0] from test_subscripting;
+
+UPDATE test_subscripting SET data[1] = 3;
-- 
2.21.0

>From a8817da97cd31b609a0d135d9e47234d5bd11694 Mon Sep 17 00:00:00 2001
From: Dmitrii Dolgov <9erthali...@gmail.com>
Date: Tue, 4 Aug 2020 17:41:42 +0200
Subject: [PATCH v35 5/5] Filling gaps in jsonb arrays

Introduces two new modes for jsonb assignment:

* Appending array elements on the specified position, gaps filled with
nulls (similar to JavaScript behavior).

* Assigning keeps array positions consistent by prevent prepending of
elements.

Originally proposed by Nikita Glukhov based on polymorphic subscripting
patch, but transformed into an independent change.
---
 src/backend/utils/adt/jsonfuncs.c   | 72 +++++++++++++++++++++++++----
 src/test/regress/expected/jsonb.out | 35 ++++++++++++++
 src/test/regress/sql/jsonb.sql      | 20 ++++++++
 3 files changed, 119 insertions(+), 8 deletions(-)

diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index 37508061a1..5fe234b88a 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -47,6 +47,8 @@
 #define JB_PATH_INSERT_AFTER			0x0010
 #define JB_PATH_CREATE_OR_INSERT \
 	(JB_PATH_INSERT_BEFORE | JB_PATH_INSERT_AFTER | JB_PATH_CREATE)
+#define JB_PATH_FILL_GAPS				0x0020
+#define JB_PATH_CONSISTENT_POSITION		0x0040
 
 /* state for json_object_keys */
 typedef struct OkeysState
@@ -1492,10 +1494,8 @@ get_jsonb_path_all(FunctionCallInfo fcinfo, bool as_text)
 static Datum
 jsonb_get_element(Jsonb *jb, Datum *path, int npath, bool *isnull, bool as_text)
 {
-	Jsonb		   *res;
 	JsonbContainer *container = &jb->root;
 	JsonbValue	   *jbvp = NULL;
-	JsonbValue		tv;
 	int				i;
 	bool			have_object = false,
 					have_array = false;
@@ -1656,14 +1656,26 @@ jsonb_set_element(Datum jsonbdatum, Datum *path, int path_len,
 
 	it = JsonbIteratorInit(&jb->root);
 
-	res = setPath(&it, path, path_nulls, path_len, &state, 0,
-				  newval, JB_PATH_CREATE);
+	res = setPath(&it, path, path_nulls, path_len, &state, 0, newval,
+				  JB_PATH_CREATE | JB_PATH_FILL_GAPS |
+				  JB_PATH_CONSISTENT_POSITION);
 
 	pfree(path_nulls);
 
 	PG_RETURN_JSONB_P(JsonbValueToJsonb(res));
 }
 
+static void
+push_null_elements(JsonbParseState **ps, int num)
+{
+		JsonbValue	null;
+
+		null.type = jbvNull;
+
+		while (num-- > 0)
+				pushJsonbValue(ps, WJB_ELEM, &null);
+}
+
 /*
  * Return the text representation of the given JsonbValue.
  */
@@ -4809,6 +4821,19 @@ IteratorConcat(JsonbIterator **it1, JsonbIterator **it2,
  * Bits JB_PATH_INSERT_BEFORE and JB_PATH_INSERT_AFTER in op_type
  * behave as JB_PATH_CREATE if new value is inserted in JsonbObject.
  *
+ * If JB_PATH_FILL_GAPS bit is set, this will change an assignment logic in
+ * case if target is an array. The assignment index will not be restricted by
+ * number of elements in the array, and if there are any empty slots between
+ * last element of the array and a new one they will be filled with nulls. If
+ * the index is negative, it still will be considered an an index from the end
+ * of the array.
+ *
+ * JB_PATH_CONSISTENT_POSITION for an array indicates that the called wants to
+ * keep values with fixed indices. Indices for existing elements could be
+ * changed (shifted forward) in case if the array is prepended with a new value
+ * and a negative index out of the range, so this behavior will be prevented
+ * and return an error.
+ *
  * All path elements before the last must already exist
  * whatever bits in op_type are set, or nothing is done.
  */
@@ -5005,25 +5030,48 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 	if (idx < 0)
 	{
 		if (-idx > nelems)
-			idx = INT_MIN;
+		{
+			/*
+			 * If asked to keep elements position consistent, it's not allowed
+			 * to prepend the array.
+			 */
+			if (op_type & JB_PATH_CONSISTENT_POSITION)
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("path element at position %d is out of range: %d",
+								level + 1, idx)));
+			else
+				idx = INT_MIN;
+		}
 		else
 			idx = nelems + idx;
 	}
 
-	if (idx > 0 && idx > nelems)
-		idx = nelems;
+	/*
+	 * Filling the gaps means there are no limits on the positive index are
+	 * imposed, we can set any element. Otherwise limit the index by nelems.
+	 */
+	if (!(op_type & JB_PATH_FILL_GAPS))
+	{
+		if (idx > 0 && idx > nelems)
+			idx = nelems;
+	}
 
 	/*
 	 * if we're creating, and idx == INT_MIN, we prepend the new value to the
 	 * array also if the array is empty - in which case we don't really care
 	 * what the idx value is
 	 */
-
 	if ((idx == INT_MIN || nelems == 0) && (level == path_len - 1) &&
 		(op_type & JB_PATH_CREATE_OR_INSERT))
 	{
 		Assert(newval != NULL);
+
+		if (op_type & JB_PATH_FILL_GAPS && nelems == 0 && idx > 0)
+			push_null_elements(st, idx);
+
 		(void) pushJsonbValue(st, WJB_ELEM, newval);
+
 		done = true;
 	}
 
@@ -5084,10 +5132,18 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 			if ((op_type & JB_PATH_CREATE_OR_INSERT) && !done &&
 				level == path_len - 1 && i == nelems - 1)
 			{
+				/*
+				 * If asked to fill the gaps, idx could be bigger than nelems,
+				 * so prepend the new element with nulls if that's the case.
+				 */
+				if (op_type & JB_PATH_FILL_GAPS && idx > nelems)
+					push_null_elements(st, idx - nelems);
+
 				(void) pushJsonbValue(st, WJB_ELEM, newval);
 			}
 		}
 	}
+
 }
 
 /*
diff --git a/src/test/regress/expected/jsonb.out b/src/test/regress/expected/jsonb.out
index 04a146a7d0..b294a56461 100644
--- a/src/test/regress/expected/jsonb.out
+++ b/src/test/regress/expected/jsonb.out
@@ -4928,6 +4928,41 @@ select * from test_jsonb_subscript;
   2 | {"a": [1, 2, 3], "key": "value", "another_key": null}
 (2 rows)
 
+-- Fill the gaps logic
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[0]');
+update test_jsonb_subscript set test_json[5] = 1;
+select * from test_jsonb_subscript;
+ id |           test_json            
+----+--------------------------------
+  1 | [0, null, null, null, null, 1]
+(1 row)
+
+update test_jsonb_subscript set test_json[-4] = 1;
+select * from test_jsonb_subscript;
+ id |          test_json          
+----+-----------------------------
+  1 | [0, null, 1, null, null, 1]
+(1 row)
+
+update test_jsonb_subscript set test_json[-8] = 1;
+ERROR:  path element at position 1 is out of range: -8
+select * from test_jsonb_subscript;
+ id |          test_json          
+----+-----------------------------
+  1 | [0, null, 1, null, null, 1]
+(1 row)
+
+-- keep consistent values position
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[]');
+update test_jsonb_subscript set test_json[5] = 1;
+select * from test_jsonb_subscript;
+ id |             test_json             
+----+-----------------------------------
+  1 | [null, null, null, null, null, 1]
+(1 row)
+
 -- jsonb to tsvector
 select to_tsvector('{"a": "aaa bbb ddd ccc", "b": ["eee fff ggg"], "c": {"d": "hhh iii"}}'::jsonb);
                                 to_tsvector                                
diff --git a/src/test/regress/sql/jsonb.sql b/src/test/regress/sql/jsonb.sql
index 12541e7e50..468a9138dc 100644
--- a/src/test/regress/sql/jsonb.sql
+++ b/src/test/regress/sql/jsonb.sql
@@ -1269,6 +1269,26 @@ update test_jsonb_subscript set test_json[NULL] = 1;
 update test_jsonb_subscript set test_json['another_key'] = NULL;
 select * from test_jsonb_subscript;
 
+-- Fill the gaps logic
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[0]');
+
+update test_jsonb_subscript set test_json[5] = 1;
+select * from test_jsonb_subscript;
+
+update test_jsonb_subscript set test_json[-4] = 1;
+select * from test_jsonb_subscript;
+
+update test_jsonb_subscript set test_json[-8] = 1;
+select * from test_jsonb_subscript;
+
+-- keep consistent values position
+delete from test_jsonb_subscript;
+insert into test_jsonb_subscript values (1, '[]');
+
+update test_jsonb_subscript set test_json[5] = 1;
+select * from test_jsonb_subscript;
+
 -- jsonb to tsvector
 select to_tsvector('{"a": "aaa bbb ddd ccc", "b": ["eee fff ggg"], "c": {"d": "hhh iii"}}'::jsonb);
 
-- 
2.21.0

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