Le mercredi 21 juillet 2021, 11:05:14 CEST Ronan Dunklau a écrit :
> Le mercredi 21 juillet 2021, 04:25:00 CEST David Rowley a écrit :
> > Here the test claims that it wants to ensure that the order by using
> > operator(public.<^) is not pushed down into the foreign scan.
> > However, unless I'm mistaken, it seems there's a completely wrong
> > assumption there that the planner would even attempt that. In current
> > master we don't add PathKeys for ORDER BY aggregates, why would that
> > sort get pushed down in the first place?
>
> The whole aggregate, including it's order by clause, can be pushed down so
> there is nothing related to pathkeys here.
>
> > If I adjust that query to something that would have the planner set
> > pathkeys for, it does push the ORDER BY to the foreign server without
> > any consideration that the sort operator is not shippable to the
> > foreign server.
> >
> > Am I missing something here, or is postgres_fdw.c's
> > get_useful_pathkeys_for_relation() just broken?
>
> I think you're right, we need to add a check if the opfamily is shippable.
> I'll submit a patch for that including regression tests.
>
In fact the support for generating the correct USING clause was inexistent
too, so that needed a bit more work.
The attached patch does the following:
- verify the opfamily is shippable to keep pathkeys
- generate a correct order by clause using the actual operator.
The second part needed a bit of refactoring: the find_em_expr_for_input_target
and find_em_expr_for_rel need to return the whole EquivalenceMember, because we
can't know the type used by the opfamily from the expression (example: the
expression could be of type intarray, but the type used by the opfamily could
be anyarray).
I also moved the "USING <operator>"' string generation to a separate function
since it's now used by appendAggOrderBy and appendOrderByClause.
The find_em_expr_for_rel is exposed in optimizer/paths.h, so I kept the
existing function which returns the expr directly in case it is used out of
tree.
--
Ronan Dunklau
commit 2376cc6656853987e8f08e9b8f444bf391a9c269
Author: Ronan Dunklau <ronan.dunk...@aiven.io>
Date: Wed Jul 21 12:44:41 2021 +0200
Fix postgres_fdw PathKey's handling.
The operator family being used for the sort was completely
ignored, and as such its existence on the foreign server was not
checked.
diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c
index 31919fda8c..2c986d3325 100644
--- a/contrib/postgres_fdw/deparse.c
+++ b/contrib/postgres_fdw/deparse.c
@@ -37,9 +37,11 @@
#include "access/sysattr.h"
#include "access/table.h"
#include "catalog/pg_aggregate.h"
+#include "catalog/pg_amop.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_operator.h"
+#include "catalog/pg_opfamily.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
@@ -180,6 +182,7 @@ static void deparseRangeTblRef(StringInfo buf, PlannerInfo
*root,
Index ignore_rel,
List **ignore_conds, List **params_list);
static void deparseAggref(Aggref *node, deparse_expr_cxt *context);
static void appendGroupByClause(List *tlist, deparse_expr_cxt *context);
+static void appendOrderbyUsingClause(Oid sortop, Oid sortcoltype,
deparse_expr_cxt *context);
static void appendAggOrderBy(List *orderList, List *targetList,
deparse_expr_cxt
*context);
static void appendFunctionName(Oid funcid, deparse_expr_cxt *context);
@@ -910,6 +913,26 @@ is_foreign_param(PlannerInfo *root,
return false;
}
+/* Returns true if the given pathkey can be evaluated on the remote side
+ */
+bool
+is_foreign_pathkey(PlannerInfo *root,
+ RelOptInfo *baserel,
+ PathKey *pathkey)
+{
+ EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
+ EquivalenceMember *em;
+ PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private;
+
+ if (pathkey_ec->ec_has_volatile)
+ return false;
+ return (!pathkey_ec->ec_has_volatile &&
+ (em = find_em_for_rel(pathkey_ec, baserel)) &&
+ is_foreign_expr(root, baserel, em->em_expr) &&
+ is_shippable(pathkey->pk_opfamily,
OperatorFamilyRelationId, fpinfo));
+}
+
+
/*
* Convert type OID + typmod info into a type name we can ship to the remote
* server. Someplace else had better have verified that this type name is
@@ -3125,6 +3148,37 @@ deparseAggref(Aggref *node, deparse_expr_cxt *context)
appendStringInfoChar(buf, ')');
}
+/*
+ * Append the USING <OPERATOR> part of an ORDER BY clause
+ */
+static void
+appendOrderbyUsingClause(Oid sortop, Oid sortcoltype, deparse_expr_cxt
*context)
+{
+ StringInfo buf = context->buf;
+ TypeCacheEntry *typentry;
+ typentry = lookup_type_cache(sortcoltype, TYPECACHE_LT_OPR |
TYPECACHE_GT_OPR);
+
+ if (sortop == typentry->lt_opr)
+ appendStringInfoString(buf, " ASC");
+ else if (sortop == typentry->gt_opr)
+ appendStringInfoString(buf, " DESC");
+ else
+ {
+ HeapTuple opertup;
+ Form_pg_operator operform;
+
+ appendStringInfoString(buf, " USING ");
+
+ /* Append operator name. */
+ opertup = SearchSysCache1(OPEROID, ObjectIdGetDatum(sortop));
+ if (!HeapTupleIsValid(opertup))
+ elog(ERROR, "cache lookup failed for operator %u",
sortop);
+ operform = (Form_pg_operator) GETSTRUCT(opertup);
+ deparseOperatorName(buf, operform);
+ ReleaseSysCache(opertup);
+ }
+}
+
/*
* Append ORDER BY within aggregate function.
*/
@@ -3140,7 +3194,6 @@ appendAggOrderBy(List *orderList, List *targetList,
deparse_expr_cxt *context)
SortGroupClause *srt = (SortGroupClause *) lfirst(lc);
Node *sortexpr;
Oid sortcoltype;
- TypeCacheEntry *typentry;
if (!first)
appendStringInfoString(buf, ", ");
@@ -3150,27 +3203,7 @@ appendAggOrderBy(List *orderList, List *targetList,
deparse_expr_cxt *context)
false, context);
sortcoltype = exprType(sortexpr);
/* See whether operator is default < or > for datatype */
- typentry = lookup_type_cache(sortcoltype,
-
TYPECACHE_LT_OPR | TYPECACHE_GT_OPR);
- if (srt->sortop == typentry->lt_opr)
- appendStringInfoString(buf, " ASC");
- else if (srt->sortop == typentry->gt_opr)
- appendStringInfoString(buf, " DESC");
- else
- {
- HeapTuple opertup;
- Form_pg_operator operform;
-
- appendStringInfoString(buf, " USING ");
-
- /* Append operator name. */
- opertup = SearchSysCache1(OPEROID,
ObjectIdGetDatum(srt->sortop));
- if (!HeapTupleIsValid(opertup))
- elog(ERROR, "cache lookup failed for operator
%u", srt->sortop);
- operform = (Form_pg_operator) GETSTRUCT(opertup);
- deparseOperatorName(buf, operform);
- ReleaseSysCache(opertup);
- }
+ appendOrderbyUsingClause(srt->sortop, sortcoltype, context);
if (srt->nulls_first)
appendStringInfoString(buf, " NULLS FIRST");
@@ -3280,7 +3313,11 @@ appendOrderByClause(List *pathkeys, bool has_final_sort,
foreach(lcell, pathkeys)
{
PathKey *pathkey = lfirst(lcell);
+ EquivalenceMember *em;
Expr *em_expr;
+ HeapTuple tuple;
+ Oid oprid;
+ bool isNull;
if (has_final_sort)
{
@@ -3288,21 +3325,44 @@ appendOrderByClause(List *pathkeys, bool has_final_sort,
* By construction, context->foreignrel is the input
relation to
* the final sort.
*/
- em_expr = find_em_expr_for_input_target(context->root,
-
pathkey->pk_eclass,
-
context->foreignrel->reltarget);
+ em = find_em_for_input_target(context->root,
+
pathkey->pk_eclass,
+
context->foreignrel->reltarget);
}
else
- em_expr = find_em_expr_for_rel(pathkey->pk_eclass,
baserel);
+ em = find_em_for_rel(pathkey->pk_eclass, baserel);
+ em_expr = em->em_expr;
+
+ /*
+ * Lookup the operator corresponding to the strategy in the
opclass.
+ * The datatype used by the opfamily is not necessarily the
same as
+ * the expression type (for array types for example).
+ */
+ tuple = SearchSysCache4(AMOPSTRATEGY,
+
ObjectIdGetDatum(pathkey->pk_opfamily),
+ em->em_datatype,
+ em->em_datatype,
+
pathkey->pk_strategy);
+ if (!HeapTupleIsValid(tuple))
+ {
+ elog(ERROR, "cache lookup failed for operator family
%u", pathkey->pk_opfamily);
+ }
+
+ oprid = DatumGetObjectId(SysCacheGetAttr(AMOPSTRATEGY, tuple,
+
Anum_pg_amop_amopopr, &isNull));
+ ReleaseSysCache(tuple);
+
Assert(em_expr != NULL);
appendStringInfoString(buf, delim);
deparseExpr(em_expr, context);
- if (pathkey->pk_strategy == BTLessStrategyNumber)
- appendStringInfoString(buf, " ASC");
- else
- appendStringInfoString(buf, " DESC");
+
+ /*
+ * Here we need to use the expression type to compare against
the
+ * default btree sort operator
+ */
+ appendOrderbyUsingClause(oprid, exprType((Node *) em_expr),
context);
if (pathkey->pk_nulls_first)
appendStringInfoString(buf, " NULLS FIRST");
diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out
b/contrib/postgres_fdw/expected/postgres_fdw.out
index ed25e7a743..66bada908f 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -3168,6 +3168,18 @@ select array_agg(c1 order by c1 using
operator(public.<^)) from ft2 where c2 = 6
Remote SQL: SELECT "C 1", c2 FROM "S 1"."T 1" WHERE (("C 1" < 100))
AND ((c2 = 6))
(6 rows)
+-- This will not be pushed either
+explain verbose select * from ft2 order by c1 using operator(public.<^);
+ QUERY PLAN
+-------------------------------------------------------------------------------
+ Sort (cost=190.83..193.33 rows=1000 width=142)
+ Output: c1, c2, c3, c4, c5, c6, c7, c8
+ Sort Key: ft2.c1 USING <^
+ -> Foreign Scan on public.ft2 (cost=100.00..141.00 rows=1000 width=47)
+ Output: c1, c2, c3, c4, c5, c6, c7, c8
+ Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1"
+(6 rows)
+
-- Update local stats on ft2
ANALYZE ft2;
-- Add into extension
@@ -3195,6 +3207,15 @@ select array_agg(c1 order by c1 using
operator(public.<^)) from ft2 where c2 = 6
{6,16,26,36,46,56,66,76,86,96}
(1 row)
+-- And this will be pushed too
+explain verbose select * from ft2 order by c1 using operator(public.<^);
+ QUERY PLAN
+-----------------------------------------------------------------------------------------------------------------------------
+ Foreign Scan on public.ft2 (cost=170.83..193.33 rows=1000 width=47)
+ Output: c1, c2, c3, c4, c5, c6, c7, c8
+ Remote SQL: SELECT "C 1", c2, c3, c4, c5, c6, c7, c8 FROM "S 1"."T 1" ORDER
BY "C 1" USING OPERATOR(public.<^) NULLS LAST
+(3 rows)
+
-- Remove from extension
alter extension postgres_fdw drop operator class my_op_class using btree;
alter extension postgres_fdw drop function my_op_cmp(a int, b int);
diff --git a/contrib/postgres_fdw/postgres_fdw.c
b/contrib/postgres_fdw/postgres_fdw.c
index f15c97ad7a..9922ee614c 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -916,8 +916,6 @@ get_useful_pathkeys_for_relation(PlannerInfo *root,
RelOptInfo *rel)
foreach(lc, root->query_pathkeys)
{
PathKey *pathkey = (PathKey *) lfirst(lc);
- EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
- Expr *em_expr;
/*
* The planner and executor don't have any clever
strategy for
@@ -929,9 +927,7 @@ get_useful_pathkeys_for_relation(PlannerInfo *root,
RelOptInfo *rel)
* is_foreign_expr would detect volatile expressions as
well, but
* checking ec_has_volatile here saves some cycles.
*/
- if (pathkey_ec->ec_has_volatile ||
- !(em_expr = find_em_expr_for_rel(pathkey_ec,
rel)) ||
- !is_foreign_expr(root, rel, em_expr))
+ if (!is_foreign_pathkey(root, rel, pathkey))
{
query_pathkeys_ok = false;
break;
@@ -6510,9 +6506,9 @@ add_foreign_ordered_paths(PlannerInfo *root, RelOptInfo
*input_rel,
return;
/* Get the sort expression for the pathkey_ec */
- sort_expr = find_em_expr_for_input_target(root,
+ sort_expr = find_em_for_input_target(root,
pathkey_ec,
-
input_rel->reltarget);
+
input_rel->reltarget)->em_expr;
/* If it's unsafe to remote, we cannot push down the final sort
*/
if (!is_foreign_expr(root, input_rel, sort_expr))
@@ -7250,11 +7246,11 @@ conversion_error_callback(void *arg)
}
/*
- * Find an equivalence class member expression to be computed as a sort column
+ * Find an equivalence class member to be computed as a sort column
* in the given target.
*/
-Expr *
-find_em_expr_for_input_target(PlannerInfo *root,
+EquivalenceMember*
+find_em_for_input_target(PlannerInfo *root,
EquivalenceClass *ec,
PathTarget *target)
{
@@ -7301,7 +7297,7 @@ find_em_expr_for_input_target(PlannerInfo *root,
em_expr = ((RelabelType *) em_expr)->arg;
if (equal(em_expr, expr))
- return em->em_expr;
+ return em;
}
i++;
diff --git a/contrib/postgres_fdw/postgres_fdw.h
b/contrib/postgres_fdw/postgres_fdw.h
index 9591c0f6c2..a0d5c859da 100644
--- a/contrib/postgres_fdw/postgres_fdw.h
+++ b/contrib/postgres_fdw/postgres_fdw.h
@@ -165,12 +165,17 @@ extern void classifyConditions(PlannerInfo *root,
List *input_conds,
List **remote_conds,
List **local_conds);
+
extern bool is_foreign_expr(PlannerInfo *root,
RelOptInfo *baserel,
Expr *expr);
extern bool is_foreign_param(PlannerInfo *root,
RelOptInfo *baserel,
Expr *expr);
+extern bool is_foreign_pathkey(PlannerInfo *root,
+ RelOptInfo *baserel,
+ PathKey *pathkey);
+
extern void deparseInsertSql(StringInfo buf, RangeTblEntry *rte,
Index rtindex,
Relation rel,
List *targetAttrs,
bool doNothing,
@@ -212,8 +217,8 @@ extern void deparseTruncateSql(StringInfo buf,
DropBehavior
behavior,
bool restart_seqs);
extern void deparseStringLiteral(StringInfo buf, const char *val);
-extern Expr *find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel);
-extern Expr *find_em_expr_for_input_target(PlannerInfo *root,
+extern EquivalenceMember *find_em_for_rel(EquivalenceClass *ec, RelOptInfo
*rel);
+extern EquivalenceMember *find_em_for_input_target(PlannerInfo *root,
EquivalenceClass *ec,
PathTarget *target);
extern List *build_tlist_to_deparse(RelOptInfo *foreignrel);
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql
b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 02a6b15a13..841fac84e4 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -873,6 +873,9 @@ create operator class my_op_class for type int using btree
family my_op_family a
explain (verbose, costs off)
select array_agg(c1 order by c1 using operator(public.<^)) from ft2 where c2 =
6 and c1 < 100 group by c2;
+-- This will not be pushed either
+explain verbose select * from ft2 order by c1 using operator(public.<^);
+
-- Update local stats on ft2
ANALYZE ft2;
@@ -890,6 +893,9 @@ explain (verbose, costs off)
select array_agg(c1 order by c1 using operator(public.<^)) from ft2 where c2 =
6 and c1 < 100 group by c2;
select array_agg(c1 order by c1 using operator(public.<^)) from ft2 where c2 =
6 and c1 < 100 group by c2;
+-- And this will be pushed too
+explain verbose select * from ft2 order by c1 using operator(public.<^);
+
-- Remove from extension
alter extension postgres_fdw drop operator class my_op_class using btree;
alter extension postgres_fdw drop function my_op_cmp(a int, b int);
diff --git a/src/backend/optimizer/path/equivclass.c
b/src/backend/optimizer/path/equivclass.c
index 6f1abbe47d..d2eac89528 100644
--- a/src/backend/optimizer/path/equivclass.c
+++ b/src/backend/optimizer/path/equivclass.c
@@ -935,8 +935,8 @@ is_exprlist_member(Expr *node, List *exprs)
* Find an equivalence class member expression, all of whose Vars, come from
* the indicated relation.
*/
-Expr *
-find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
+EquivalenceMember*
+find_em_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
{
ListCell *lc_em;
@@ -952,7 +952,7 @@ find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
* taken entirely from this relation, we'll be content
to choose
* any one of those.
*/
- return em->em_expr;
+ return em;
}
}
@@ -960,6 +960,14 @@ find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
return NULL;
}
+Expr *
+find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
+{
+ EquivalenceMember *em = find_em_for_rel(ec, rel);
+ return em ? em->em_expr : NULL;
+}
+
+
/*
* relation_can_be_sorted_early
* Can this relation be sorted on this EC before the final output
step?
diff --git a/src/include/optimizer/paths.h b/src/include/optimizer/paths.h
index f1d111063c..bc17114ba3 100644
--- a/src/include/optimizer/paths.h
+++ b/src/include/optimizer/paths.h
@@ -144,6 +144,7 @@ extern EquivalenceMember
*find_computable_ec_member(PlannerInfo *root,
Relids relids,
bool require_parallel_safe);
extern Expr *find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel);
+extern EquivalenceMember *find_em_for_rel(EquivalenceClass *ec, RelOptInfo
*rel);
extern bool relation_can_be_sorted_early(PlannerInfo *root, RelOptInfo *rel,
EquivalenceClass *ec,
bool require_parallel_safe);
