On Sun, Mar 31, 2019 at 3:14 AM Tomas Vondra <tomas.von...@2ndquadrant.com>
wrote:
>
>
> Hi,
>
> I got to look at the patch today, with the intent to commit, but sadly I
> ran into a couple of minor issues that I don't feel comfortable fixing
> on my own. Attached is a patch highlighling some of the places (0001 is
> your v7 patch, to keep the cfbot happy).
>
>
Thank you
>
> 1) the docs documented this as
>
> ... [ ONLY | WITH TIES ]
>
> but that's wrong, because it implies those options are optional (i.e.
> the user may not specify anything). That's not the case, exactly one
> of those options needs to be specified, so it should have been
>
> ... { ONLY | WITH TIES }
>
>
> 2) The comment in ExecLimit() needs to be updated to explain that WITH
> TIES changes the behavior.
>
>
> 3) Minor code style issues (no space before * on comment lines, {}
> around single-line if statements, ...).
>
>
> 4) The ExecLimit() does this
>
> if (node->limitOption == WITH_TIES)
> ExecCopySlot(node->last_slot, slot);
>
> but I think we only really need to do that for the last tuple in the
> window, no? Would it be a useful optimization?
>
>
>
I think it is good optimization .Fixed
5) Two issues in _outLimit(). Firstly, when printing uniqCollations the
> code actually prints uniqOperators. Secondly, why does the code use
> these loops at all, instead of using WRITE_ATTRNUMBER_ARRAY and
> WRITE_OID_ARRAY, like other places? Perhaps there's an issue with empty
> arrays? I haven't tested this, but looking at the READ_ counterparts, I
> don't see why that would be the case.
>
>
>
Fixed
regards
Surafel
diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 06d611b64c..e83d309c5b 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -44,7 +44,7 @@ SELECT [ ALL | DISTINCT [ ON ( <replaceable class="parameter">expression</replac
[ ORDER BY <replaceable class="parameter">expression</replaceable> [ ASC | DESC | USING <replaceable class="parameter">operator</replaceable> ] [ NULLS { FIRST | LAST } ] [, ...] ]
[ LIMIT { <replaceable class="parameter">count</replaceable> | ALL } ]
[ OFFSET <replaceable class="parameter">start</replaceable> [ ROW | ROWS ] ]
- [ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY ]
+ [ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } { ONLY | WITH TIES } ]
[ FOR { UPDATE | NO KEY UPDATE | SHARE | KEY SHARE } [ OF <replaceable class="parameter">table_name</replaceable> [, ...] ] [ NOWAIT | SKIP LOCKED ] [...] ]
<phrase>where <replaceable class="parameter">from_item</replaceable> can be one of:</phrase>
@@ -1430,7 +1430,7 @@ OFFSET <replaceable class="parameter">start</replaceable>
which <productname>PostgreSQL</productname> also supports. It is:
<synopsis>
OFFSET <replaceable class="parameter">start</replaceable> { ROW | ROWS }
-FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } ONLY
+FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] { ROW | ROWS } { ONLY | WITH TIES }
</synopsis>
In this syntax, the <replaceable class="parameter">start</replaceable>
or <replaceable class="parameter">count</replaceable> value is required by
@@ -1440,7 +1440,10 @@ FETCH { FIRST | NEXT } [ <replaceable class="parameter">count</replaceable> ] {
ambiguity.
If <replaceable class="parameter">count</replaceable> is
omitted in a <literal>FETCH</literal> clause, it defaults to 1.
- <literal>ROW</literal>
+ <literal>ROW</literal> .
+ <literal>WITH TIES</literal> option is used to return two or more rows
+ that tie for the last place in the result set according to <literal>ORDER BY</literal>
+ clause (<literal>ORDER BY</literal> clause must be specified in this case).
and <literal>ROWS</literal> as well as <literal>FIRST</literal>
and <literal>NEXT</literal> are noise words that don't influence
the effects of these clauses.
diff --git a/src/backend/executor/nodeLimit.c b/src/backend/executor/nodeLimit.c
index baa669abe8..994ac7f089 100644
--- a/src/backend/executor/nodeLimit.c
+++ b/src/backend/executor/nodeLimit.c
@@ -41,6 +41,7 @@ static TupleTableSlot * /* return: a tuple or NULL */
ExecLimit(PlanState *pstate)
{
LimitState *node = castNode(LimitState, pstate);
+ ExprContext *econtext = node->ps.ps_ExprContext;
ScanDirection direction;
TupleTableSlot *slot;
PlanState *outerPlan;
@@ -126,12 +127,16 @@ ExecLimit(PlanState *pstate)
{
/*
* Forwards scan, so check for stepping off end of window. If
- * we are at the end of the window, return NULL without
- * advancing the subplan or the position variable; but change
- * the state machine state to record having done so.
+ * we are at the end of the window, the behavior depends whether
+ * ONLY or WITH TIES was specified. In case of ONLY, we return
+ * NULL without advancing the subplan or the position variable;
+ * but change the state machine state to record having done so.
+ * In the WITH TIES mode, we need to advance the subplan until
+ * we find the first row with different ORDER BY pathkeys.
*/
if (!node->noCount &&
- node->position - node->offset >= node->count)
+ node->position - node->offset >= node->count &&
+ node->limitOption == EXACT_NUMBER)
{
node->lstate = LIMIT_WINDOWEND;
@@ -144,18 +149,69 @@ ExecLimit(PlanState *pstate)
return NULL;
}
+ else if (!node->noCount &&
+ node->position - node->offset >= node->count &&
+ node->limitOption == WITH_TIES)
+ {
+ /*
+ * Get next tuple from subplan, if any.
+ */
+ slot = ExecProcNode(outerPlan);
+ if (TupIsNull(slot))
+ {
+ node->lstate = LIMIT_SUBPLANEOF;
+ return NULL;
+ }
+ /*
+ * Test if the new tuple and the last tuple match.
+ * If so we return the tuple.
+ */
+ econtext->ecxt_innertuple = slot;
+ econtext->ecxt_outertuple = node->last_slot;
+ if (ExecQualAndReset(node->eqfunction, econtext))
+ {
+ node->subSlot = slot;
+ node->position++;
+ }
+ else
+ {
+ node->lstate = LIMIT_WINDOWEND;
+
+ /*
+ * If we know we won't need to back up, we can release
+ * resources at this point.
+ */
+ if (!(node->ps.state->es_top_eflags & EXEC_FLAG_BACKWARD))
+ (void) ExecShutdownNode(outerPlan);
+
+ return NULL;
+ }
- /*
- * Get next tuple from subplan, if any.
- */
- slot = ExecProcNode(outerPlan);
- if (TupIsNull(slot))
+ }
+ else
{
- node->lstate = LIMIT_SUBPLANEOF;
- return NULL;
+ /*
+ * Get next tuple from subplan, if any.
+ */
+ slot = ExecProcNode(outerPlan);
+ if (TupIsNull(slot))
+ {
+ node->lstate = LIMIT_SUBPLANEOF;
+ return NULL;
+ }
+
+ /*
+ * Tuple at limit is needed for comparation in subsequent execution
+ * to detect ties.
+ */
+ if (node->limitOption == WITH_TIES &&
+ node->position - node->offset == node->count - 1)
+ {
+ ExecCopySlot(node->last_slot, slot);
+ }
+ node->subSlot = slot;
+ node->position++;
}
- node->subSlot = slot;
- node->position++;
}
else
{
@@ -309,9 +365,10 @@ recompute_limits(LimitState *node)
* Notify child node about limit. Note: think not to "optimize" by
* skipping ExecSetTupleBound if compute_tuples_needed returns < 0. We
* must update the child node anyway, in case this is a rescan and the
- * previous time we got a different result.
+ * previous time we got a different result.In WITH TIES option we may exceed limit
*/
- ExecSetTupleBound(compute_tuples_needed(node), outerPlanState(node));
+ if(node->limitOption == EXACT_NUMBER)
+ ExecSetTupleBound(compute_tuples_needed(node), outerPlanState(node));
}
/*
@@ -374,6 +431,7 @@ ExecInitLimit(Limit *node, EState *estate, int eflags)
(PlanState *) limitstate);
limitstate->limitCount = ExecInitExpr((Expr *) node->limitCount,
(PlanState *) limitstate);
+ limitstate->limitOption = node->limitOption;
/*
* Initialize result type.
@@ -390,6 +448,25 @@ ExecInitLimit(Limit *node, EState *estate, int eflags)
*/
limitstate->ps.ps_ProjInfo = NULL;
+ /*
+ * Initialize the equality evaluation, to detect ties.
+ */
+ if (node->limitOption == WITH_TIES)
+ {
+ TupleDesc scanDesc;
+ const TupleTableSlotOps *ops;
+ scanDesc = limitstate->ps.ps_ResultTupleDesc;
+ ops = ExecGetResultSlotOps(outerPlanState(limitstate), NULL);
+ limitstate->last_slot = ExecInitExtraTupleSlot(estate, scanDesc, ops);
+ limitstate->eqfunction =
+ execTuplesMatchPrepare(ExecGetResultType(outerPlanState(limitstate)),
+ node->uniqNumCols,
+ node->uniqColIdx,
+ node->uniqOperators,
+ node->uniqCollations,
+ &limitstate->ps);
+ }
+
return limitstate;
}
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 04cc15606d..216392883f 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -1143,6 +1143,11 @@ _copyLimit(const Limit *from)
*/
COPY_NODE_FIELD(limitOffset);
COPY_NODE_FIELD(limitCount);
+ COPY_SCALAR_FIELD(limitOption);
+ COPY_SCALAR_FIELD(uniqNumCols);
+ COPY_POINTER_FIELD(uniqColIdx, from->uniqNumCols * sizeof(AttrNumber));
+ COPY_POINTER_FIELD(uniqOperators, from->uniqNumCols * sizeof(Oid));
+ COPY_POINTER_FIELD(uniqCollations, from->uniqNumCols * sizeof(Oid));
return newnode;
}
@@ -3031,6 +3036,7 @@ _copyQuery(const Query *from)
COPY_NODE_FIELD(sortClause);
COPY_NODE_FIELD(limitOffset);
COPY_NODE_FIELD(limitCount);
+ COPY_SCALAR_FIELD(limitOption);
COPY_NODE_FIELD(rowMarks);
COPY_NODE_FIELD(setOperations);
COPY_NODE_FIELD(constraintDeps);
@@ -3115,6 +3121,7 @@ _copySelectStmt(const SelectStmt *from)
COPY_NODE_FIELD(sortClause);
COPY_NODE_FIELD(limitOffset);
COPY_NODE_FIELD(limitCount);
+ COPY_SCALAR_FIELD(limitOption);
COPY_NODE_FIELD(lockingClause);
COPY_NODE_FIELD(withClause);
COPY_SCALAR_FIELD(op);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 91c007ad5b..fb9048d7f5 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -975,6 +975,7 @@ _equalQuery(const Query *a, const Query *b)
COMPARE_NODE_FIELD(sortClause);
COMPARE_NODE_FIELD(limitOffset);
COMPARE_NODE_FIELD(limitCount);
+ COMPARE_SCALAR_FIELD(limitOption);
COMPARE_NODE_FIELD(rowMarks);
COMPARE_NODE_FIELD(setOperations);
COMPARE_NODE_FIELD(constraintDeps);
@@ -1049,6 +1050,7 @@ _equalSelectStmt(const SelectStmt *a, const SelectStmt *b)
COMPARE_NODE_FIELD(sortClause);
COMPARE_NODE_FIELD(limitOffset);
COMPARE_NODE_FIELD(limitCount);
+ COMPARE_SCALAR_FIELD(limitOption);
COMPARE_NODE_FIELD(lockingClause);
COMPARE_NODE_FIELD(withClause);
COMPARE_SCALAR_FIELD(op);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 910a738c20..60274b5ee0 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -907,6 +907,11 @@ _outLimit(StringInfo str, const Limit *node)
WRITE_NODE_FIELD(limitOffset);
WRITE_NODE_FIELD(limitCount);
+ WRITE_ENUM_FIELD(limitOption, LimitOption);
+ WRITE_INT_FIELD(uniqNumCols);
+ WRITE_ATTRNUMBER_ARRAY(uniqColIdx, node->uniqNumCols);
+ WRITE_OID_ARRAY(uniqOperators, node->uniqNumCols);
+ WRITE_OID_ARRAY(uniqCollations, node->uniqNumCols);
}
static void
@@ -2699,6 +2704,7 @@ _outSelectStmt(StringInfo str, const SelectStmt *node)
WRITE_NODE_FIELD(sortClause);
WRITE_NODE_FIELD(limitOffset);
WRITE_NODE_FIELD(limitCount);
+ WRITE_ENUM_FIELD(limitOption, LimitOption);
WRITE_NODE_FIELD(lockingClause);
WRITE_NODE_FIELD(withClause);
WRITE_ENUM_FIELD(op, SetOperation);
@@ -2908,6 +2914,7 @@ _outQuery(StringInfo str, const Query *node)
WRITE_NODE_FIELD(sortClause);
WRITE_NODE_FIELD(limitOffset);
WRITE_NODE_FIELD(limitCount);
+ WRITE_ENUM_FIELD(limitOption, LimitOption);
WRITE_NODE_FIELD(rowMarks);
WRITE_NODE_FIELD(setOperations);
WRITE_NODE_FIELD(constraintDeps);
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index eff98febf1..0ffa16345d 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -278,6 +278,7 @@ _readQuery(void)
READ_NODE_FIELD(sortClause);
READ_NODE_FIELD(limitOffset);
READ_NODE_FIELD(limitCount);
+ READ_ENUM_FIELD(limitOption, LimitOption);
READ_NODE_FIELD(rowMarks);
READ_NODE_FIELD(setOperations);
READ_NODE_FIELD(constraintDeps);
@@ -2332,6 +2333,11 @@ _readLimit(void)
READ_NODE_FIELD(limitOffset);
READ_NODE_FIELD(limitCount);
+ READ_ENUM_FIELD(limitOption, LimitOption);
+ READ_INT_FIELD(uniqNumCols);
+ READ_ATTRNUMBER_ARRAY(uniqColIdx, local_node->uniqNumCols);
+ READ_OID_ARRAY(uniqOperators, local_node->uniqNumCols);
+ READ_OID_ARRAY(uniqCollations, local_node->uniqNumCols);
READ_DONE();
}
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 979c3c212f..e6a47c6811 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -2201,7 +2201,9 @@ create_minmaxagg_plan(PlannerInfo *root, MinMaxAggPath *best_path)
plan = (Plan *) make_limit(plan,
subparse->limitOffset,
- subparse->limitCount);
+ subparse->limitCount,
+ subparse->limitOption,
+ 0, NULL, NULL, NULL);
/* Must apply correct cost/width data to Limit node */
plan->startup_cost = mminfo->path->startup_cost;
@@ -2508,13 +2510,43 @@ create_limit_plan(PlannerInfo *root, LimitPath *best_path, int flags)
{
Limit *plan;
Plan *subplan;
+ int numUniqkeys = 0;
+ AttrNumber *uniqColIdx = NULL;
+ Oid *uniqOperators = NULL;
+ Oid *uniqCollations = NULL;
/* Limit doesn't project, so tlist requirements pass through */
subplan = create_plan_recurse(root, best_path->subpath, flags);
+ if (best_path->limitOption == WITH_TIES)
+ {
+ Query *parse = root->parse;
+ ListCell *l;
+
+ numUniqkeys = list_length(parse->sortClause);
+ uniqColIdx = (AttrNumber *) palloc(numUniqkeys * sizeof(AttrNumber));
+ uniqOperators = (Oid *) palloc(numUniqkeys * sizeof(Oid));
+ uniqCollations = (Oid *) palloc(numUniqkeys * sizeof(Oid));
+
+ numUniqkeys = 0;
+ foreach(l, parse->sortClause)
+ {
+ SortGroupClause *sortcl = (SortGroupClause *) lfirst(l);
+ TargetEntry *tle = get_sortgroupclause_tle(sortcl, parse->targetList);
+
+ uniqColIdx[numUniqkeys] = tle->resno;
+ uniqOperators[numUniqkeys] = sortcl->eqop;
+ uniqCollations[numUniqkeys] = exprCollation((Node *) tle->expr);
+ numUniqkeys++;
+ }
+
+ }
+
plan = make_limit(subplan,
best_path->limitOffset,
- best_path->limitCount);
+ best_path->limitCount,
+ best_path->limitOption,
+ numUniqkeys, uniqColIdx, uniqOperators, uniqCollations);
copy_generic_path_info(&plan->plan, (Path *) best_path);
@@ -6399,7 +6431,8 @@ make_lockrows(Plan *lefttree, List *rowMarks, int epqParam)
* Build a Limit plan node
*/
Limit *
-make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount)
+make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount, LimitOption limitOption,
+ int uniqNumCols, AttrNumber *uniqColIdx, Oid *uniqOperators, Oid *uniqCollations)
{
Limit *node = makeNode(Limit);
Plan *plan = &node->plan;
@@ -6411,6 +6444,11 @@ make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount)
node->limitOffset = limitOffset;
node->limitCount = limitCount;
+ node->limitOption = limitOption;
+ node->uniqNumCols = uniqNumCols;
+ node->uniqColIdx = uniqColIdx;
+ node->uniqOperators = uniqOperators;
+ node->uniqCollations = uniqCollations;
return node;
}
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index e408e77d6f..a005f31546 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -2185,6 +2185,7 @@ grouping_planner(PlannerInfo *root, bool inheritance_update,
path = (Path *) create_limit_path(root, final_rel, path,
parse->limitOffset,
parse->limitCount,
+ parse->limitOption,
offset_est, count_est);
}
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 56de8fc370..5bc5924f7a 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -3554,6 +3554,7 @@ LimitPath *
create_limit_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath,
Node *limitOffset, Node *limitCount,
+ LimitOption limitOption,
int64 offset_est, int64 count_est)
{
LimitPath *pathnode = makeNode(LimitPath);
@@ -3575,6 +3576,7 @@ create_limit_path(PlannerInfo *root, RelOptInfo *rel,
pathnode->subpath = subpath;
pathnode->limitOffset = limitOffset;
pathnode->limitCount = limitCount;
+ pathnode->limitOption = limitOption;
/*
* Adjust the output rows count and costs according to the offset/limit.
@@ -3616,6 +3618,20 @@ create_limit_path(PlannerInfo *root, RelOptInfo *rel,
count_rows = (double) count_est;
else
count_rows = clamp_row_est(subpath->rows * 0.10);
+ if (limitOption == WITH_TIES)
+ {
+ double numGroups;
+ double avgGroupSize;
+ List *groupExprs;
+
+ groupExprs = get_sortgrouplist_exprs(root->parse->sortClause,
+ root->parse->targetList);
+
+ numGroups = estimate_num_groups(root, groupExprs, subpath->rows,
+ NULL);
+ avgGroupSize = subpath->rows / numGroups;
+ count_rows = Max(avgGroupSize, count_est + (avgGroupSize/2));
+ }
if (count_rows > pathnode->path.rows)
count_rows = pathnode->path.rows;
if (subpath->rows > 0)
diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index d6cdd16607..c5509af446 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -1292,6 +1292,7 @@ transformSelectStmt(ParseState *pstate, SelectStmt *stmt)
EXPR_KIND_OFFSET, "OFFSET");
qry->limitCount = transformLimitClause(pstate, stmt->limitCount,
EXPR_KIND_LIMIT, "LIMIT");
+ qry->limitOption = stmt->limitOption;
/* transform window clauses after we have seen all window functions */
qry->windowClause = transformWindowDefinitions(pstate,
@@ -1540,6 +1541,7 @@ transformValuesClause(ParseState *pstate, SelectStmt *stmt)
EXPR_KIND_OFFSET, "OFFSET");
qry->limitCount = transformLimitClause(pstate, stmt->limitCount,
EXPR_KIND_LIMIT, "LIMIT");
+ qry->limitOption = stmt->limitOption;
if (stmt->lockingClause)
ereport(ERROR,
@@ -1774,6 +1776,7 @@ transformSetOperationStmt(ParseState *pstate, SelectStmt *stmt)
EXPR_KIND_OFFSET, "OFFSET");
qry->limitCount = transformLimitClause(pstate, limitCount,
EXPR_KIND_LIMIT, "LIMIT");
+ qry->limitOption = stmt->limitOption;
qry->rtable = pstate->p_rtable;
qry->jointree = makeFromExpr(pstate->p_joinlist, NULL);
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 0a4822829a..6a7ab0bd4e 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -165,6 +165,7 @@ static List *makeOrderedSetArgs(List *directargs, List *orderedargs,
static void insertSelectOptions(SelectStmt *stmt,
List *sortClause, List *lockingClause,
Node *limitOffset, Node *limitCount,
+ void *limitOption,
WithClause *withClause,
core_yyscan_t yyscanner);
static Node *makeSetOp(SetOperation op, bool all, Node *larg, Node *rarg);
@@ -392,7 +393,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
target_list opt_target_list insert_column_list set_target_list
set_clause_list set_clause
def_list operator_def_list indirection opt_indirection
- reloption_list group_clause TriggerFuncArgs select_limit
+ reloption_list group_clause TriggerFuncArgs select_limit limit_clause
opt_select_limit opclass_item_list opclass_drop_list
opclass_purpose opt_opfamily transaction_mode_list_or_empty
OptTableFuncElementList TableFuncElementList opt_type_modifiers
@@ -454,7 +455,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
comment_type_any_name comment_type_name
security_label_type_any_name security_label_type_name
-%type <node> fetch_args limit_clause select_limit_value
+%type <node> fetch_args select_limit_value
offset_clause select_offset_value
select_fetch_first_value I_or_F_const
%type <ival> row_or_rows first_or_next
@@ -11188,7 +11189,7 @@ select_no_parens:
| select_clause sort_clause
{
insertSelectOptions((SelectStmt *) $1, $2, NIL,
- NULL, NULL, NULL,
+ NULL, NULL, NULL, NULL,
yyscanner);
$$ = $1;
}
@@ -11196,6 +11197,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $1, $2, $3,
list_nth($4, 0), list_nth($4, 1),
+ (list_nth($4, 2)),
NULL,
yyscanner);
$$ = $1;
@@ -11204,6 +11206,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $1, $2, $4,
list_nth($3, 0), list_nth($3, 1),
+ (list_nth($3, 2)),
NULL,
yyscanner);
$$ = $1;
@@ -11212,7 +11215,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $2, NULL, NIL,
NULL, NULL,
- $1,
+ NULL,$1,
yyscanner);
$$ = $2;
}
@@ -11220,7 +11223,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $2, $3, NIL,
NULL, NULL,
- $1,
+ NULL,$1,
yyscanner);
$$ = $2;
}
@@ -11228,6 +11231,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $2, $3, $4,
list_nth($5, 0), list_nth($5, 1),
+ list_nth($5, 2),
$1,
yyscanner);
$$ = $2;
@@ -11236,6 +11240,7 @@ select_no_parens:
{
insertSelectOptions((SelectStmt *) $2, $3, $5,
list_nth($4, 0), list_nth($4, 1),
+ list_nth($4, 2),
$1,
yyscanner);
$$ = $2;
@@ -11529,20 +11534,20 @@ sortby: a_expr USING qual_all_Op opt_nulls_order
select_limit:
- limit_clause offset_clause { $$ = list_make2($2, $1); }
- | offset_clause limit_clause { $$ = list_make2($1, $2); }
- | limit_clause { $$ = list_make2(NULL, $1); }
- | offset_clause { $$ = list_make2($1, NULL); }
+ limit_clause offset_clause { $$ = list_make3($2, list_nth($1, 0), list_nth($1, 1)); }
+ | offset_clause limit_clause { $$ = list_make3($1, list_nth($2, 0), list_nth($2, 1)); }
+ | limit_clause { $$ = list_make3(NULL, list_nth($1, 0), list_nth($1, 1)); }
+ | offset_clause { $$ = list_make3($1, NULL, NULL); }
;
opt_select_limit:
select_limit { $$ = $1; }
- | /* EMPTY */ { $$ = list_make2(NULL,NULL); }
+ | /* EMPTY */ { $$ = list_make3(NULL, NULL, NULL); }
;
limit_clause:
LIMIT select_limit_value
- { $$ = $2; }
+ { $$ = list_make2($2, NULL); }
| LIMIT select_limit_value ',' select_offset_value
{
/* Disabled because it was too confusing, bjm 2002-02-18 */
@@ -11560,9 +11565,11 @@ limit_clause:
* we can see the ONLY token in the lookahead slot.
*/
| FETCH first_or_next select_fetch_first_value row_or_rows ONLY
- { $$ = $3; }
+ { $$ = list_make2($3, makeString("EXACT_NUMBER")); }
+ | FETCH first_or_next select_fetch_first_value row_or_rows WITH TIES
+ { $$ = list_make2($3, makeString("WITH_TIES")); }
| FETCH first_or_next row_or_rows ONLY
- { $$ = makeIntConst(1, -1); }
+ { $$ = list_make2(makeIntConst(1, -1), NULL); }
;
offset_clause:
@@ -15818,6 +15825,7 @@ static void
insertSelectOptions(SelectStmt *stmt,
List *sortClause, List *lockingClause,
Node *limitOffset, Node *limitCount,
+ void *limitOption,
WithClause *withClause,
core_yyscan_t yyscanner)
{
@@ -15856,6 +15864,21 @@ insertSelectOptions(SelectStmt *stmt,
parser_errposition(exprLocation(limitCount))));
stmt->limitCount = limitCount;
}
+ if (limitOption)
+ {
+ if (stmt->limitOption)
+ ereport(ERROR,
+ (errcode(ERRCODE_SYNTAX_ERROR),
+ errmsg("multiple limit options not allowed")));
+ if (!stmt->sortClause && strcmp(strVal(limitOption), "WITH_TIES") == 0)
+ ereport(ERROR,
+ (errcode(ERRCODE_SYNTAX_ERROR),
+ errmsg("WITH TIES options can not be specified without ORDER BY clause")));
+ if (strcmp(strVal(limitOption), "EXACT_NUMBER") == 0)
+ stmt->limitOption = EXACT_NUMBER;
+ else
+ stmt->limitOption = WITH_TIES;
+ }
if (withClause)
{
if (stmt->withClause)
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 869c303e15..e0017adfb4 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -2291,12 +2291,15 @@ typedef struct LimitState
PlanState ps; /* its first field is NodeTag */
ExprState *limitOffset; /* OFFSET parameter, or NULL if none */
ExprState *limitCount; /* COUNT parameter, or NULL if none */
+ LimitOption limitOption; /* limit specification type */
int64 offset; /* current OFFSET value */
int64 count; /* current COUNT, if any */
bool noCount; /* if true, ignore count */
LimitStateCond lstate; /* state machine status, as above */
int64 position; /* 1-based index of last tuple returned */
TupleTableSlot *subSlot; /* tuple last obtained from subplan */
+ ExprState *eqfunction; /* tuple equality qual in case of WITH TIES option */
+ TupleTableSlot *last_slot; /* slot for evaluation of ties */
} LimitState;
#endif /* EXECNODES_H */
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index ffb4cd4bcc..f0a7aff679 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -821,4 +821,16 @@ typedef enum OnConflictAction
ONCONFLICT_UPDATE /* ON CONFLICT ... DO UPDATE */
} OnConflictAction;
+/*
+ * LimitOption -
+ * LIMIT option of query
+ *
+ * This is needed in both parsenodes.h and plannodes.h, so put it here...
+ */
+typedef enum LimitOption
+{
+ EXACT_NUMBER, /* FETCH FIRST... ONLY */
+ WITH_TIES /* FETCH FIRST... WITH TIES */
+} LimitOption;
+
#endif /* NODES_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index bdd2bd2fd9..1be35a82c1 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -159,6 +159,7 @@ typedef struct Query
Node *limitOffset; /* # of result tuples to skip (int8 expr) */
Node *limitCount; /* # of result tuples to return (int8 expr) */
+ LimitOption limitOption; /* limit type { WITH TIES | ONLY } */
List *rowMarks; /* a list of RowMarkClause's */
@@ -1583,6 +1584,7 @@ typedef struct SelectStmt
List *sortClause; /* sort clause (a list of SortBy's) */
Node *limitOffset; /* # of result tuples to skip */
Node *limitCount; /* # of result tuples to return */
+ LimitOption limitOption; /* limit type */
List *lockingClause; /* FOR UPDATE (list of LockingClause's) */
WithClause *withClause; /* WITH clause */
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 253e0b7e48..0f36b514f3 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -1780,6 +1780,7 @@ typedef struct LimitPath
Path *subpath; /* path representing input source */
Node *limitOffset; /* OFFSET parameter, or NULL if none */
Node *limitCount; /* COUNT parameter, or NULL if none */
+ LimitOption limitOption; /* FETCH FIRST with ties or exact number */
} LimitPath;
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 24740c31e3..3e38573f06 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -953,6 +953,11 @@ typedef struct Limit
Plan plan;
Node *limitOffset; /* OFFSET parameter, or NULL if none */
Node *limitCount; /* COUNT parameter, or NULL if none */
+ LimitOption limitOption; /* fetch first with ties or exact number */
+ int uniqNumCols; /* number of columns to check for Similarity */
+ AttrNumber *uniqColIdx; /* their indexes in the target list */
+ Oid *uniqOperators; /* equality operators to compare with */
+ Oid *uniqCollations; /* collations for equality comparisons */
} Limit;
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 574bb85b50..fe593170d3 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -264,6 +264,7 @@ extern ModifyTablePath *create_modifytable_path(PlannerInfo *root,
extern LimitPath *create_limit_path(PlannerInfo *root, RelOptInfo *rel,
Path *subpath,
Node *limitOffset, Node *limitCount,
+ LimitOption limitOption,
int64 offset_est, int64 count_est);
extern Path *reparameterize_path(PlannerInfo *root, Path *path,
diff --git a/src/include/optimizer/planmain.h b/src/include/optimizer/planmain.h
index b093a3c8ac..d1910268bf 100644
--- a/src/include/optimizer/planmain.h
+++ b/src/include/optimizer/planmain.h
@@ -56,7 +56,8 @@ extern Agg *make_agg(List *tlist, List *qual,
int numGroupCols, AttrNumber *grpColIdx, Oid *grpOperators, Oid *grpCollations,
List *groupingSets, List *chain,
double dNumGroups, Plan *lefttree);
-extern Limit *make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount);
+extern Limit *make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount,
+ LimitOption limitOption,int uniqNumCols, AttrNumber *uniqColIdx, Oid *uniqOperators, Oid *uniqCollations);
/*
* prototypes for plan/initsplan.c
diff --git a/src/test/regress/expected/limit.out b/src/test/regress/expected/limit.out
index c18f547cbd..199725ec7f 100644
--- a/src/test/regress/expected/limit.out
+++ b/src/test/regress/expected/limit.out
@@ -503,3 +503,38 @@ select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
45020 | 45020
(3 rows)
+--
+-- FETCH FIRST
+-- Check the WITH TIES clause
+--
+SELECT thousand
+ FROM onek WHERE thousand < 5
+ ORDER BY thousand FETCH FIRST 2 ROW WITH TIES;
+ thousand
+----------
+ 0
+ 0
+ 0
+ 0
+ 0
+ 0
+ 0
+ 0
+ 0
+ 0
+(10 rows)
+
+SELECT thousand
+ FROM onek WHERE thousand < 5
+ ORDER BY thousand FETCH FIRST 2 ROW ONLY;
+ thousand
+----------
+ 0
+ 0
+(2 rows)
+
+-- should fail
+SELECT ''::text AS two, unique1, unique2, stringu1
+ FROM onek WHERE unique1 > 50
+ FETCH FIRST 2 ROW WITH TIES;
+ERROR: WITH TIES options can not be specified without ORDER BY clause
diff --git a/src/test/regress/sql/limit.sql b/src/test/regress/sql/limit.sql
index 2a313d80ca..8009b746cb 100644
--- a/src/test/regress/sql/limit.sql
+++ b/src/test/regress/sql/limit.sql
@@ -141,3 +141,20 @@ select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
select sum(tenthous) as s1, sum(tenthous) + random()*0 as s2
from tenk1 group by thousand order by thousand limit 3;
+
+--
+-- FETCH FIRST
+-- Check the WITH TIES clause
+--
+
+SELECT thousand
+ FROM onek WHERE thousand < 5
+ ORDER BY thousand FETCH FIRST 2 ROW WITH TIES;
+
+SELECT thousand
+ FROM onek WHERE thousand < 5
+ ORDER BY thousand FETCH FIRST 2 ROW ONLY;
+-- should fail
+SELECT ''::text AS two, unique1, unique2, stringu1
+ FROM onek WHERE unique1 > 50
+ FETCH FIRST 2 ROW WITH TIES;
