Le vendredi 3 septembre 2021, 22:54:25 CEST David Zhang a écrit :
> The following review has been posted through the commitfest application:
> make installcheck-world: tested, failed
> Implements feature: tested, passed
> Spec compliant: not tested
> Documentation: not tested
>
> Applied the v6 patch to master branch and ran regression test for contrib,
> the result was "All tests successful."
What kind of error did you get running make installcheck-world ? If it passed
the make check for contrib, I can't see why it would fail running make
installcheck-world.
In any case, I just checked and running make installcheck-world doesn't
produce any error.
Since HEAD had moved a bit since the last version, I rebased the patch,
resulting in the attached v7.
Best regards,
--
Ronan Dunklau
>From ccfb0a3d7dae42f56c699aac6f699c3c2f08c812 Mon Sep 17 00:00:00 2001
From: Ronan Dunklau <ronan.dunk...@aiven.io>
Date: Mon, 6 Sep 2021 09:54:43 +0200
Subject: [PATCH v7] Fix orderby handling in postgres_fdw
The logic for pushing down order bys in postgres fdw didn't take into
account the specific operator used, and as such a pushed-down order by
could return wrong results.
---
contrib/postgres_fdw/deparse.c | 156 +++++++++++++-----
.../postgres_fdw/expected/postgres_fdw.out | 23 +++
contrib/postgres_fdw/postgres_fdw.c | 28 ++--
contrib/postgres_fdw/postgres_fdw.h | 11 +-
contrib/postgres_fdw/sql/postgres_fdw.sql | 8 +
src/backend/optimizer/path/equivclass.c | 26 ++-
src/include/optimizer/paths.h | 2 +
7 files changed, 187 insertions(+), 67 deletions(-)
diff --git a/contrib/postgres_fdw/deparse.c b/contrib/postgres_fdw/deparse.c
index d98bd66681..fb1b5f9d9b 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"
@@ -47,6 +49,7 @@
#include "nodes/nodeFuncs.h"
#include "nodes/plannodes.h"
#include "optimizer/optimizer.h"
+#include "optimizer/paths.h"
#include "optimizer/prep.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
@@ -182,6 +185,8 @@ 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 appendOrderBySuffix(Oid sortop, Oid sortcoltype, bool nulls_first,
+ deparse_expr_cxt *context);
static void appendAggOrderBy(List *orderList, List *targetList,
deparse_expr_cxt *context);
static void appendFunctionName(Oid funcid, deparse_expr_cxt *context);
@@ -1037,6 +1042,41 @@ is_foreign_param(PlannerInfo *root,
return false;
}
+/*
+ * Returns true if it's safe to push down a sort as described by 'pathkey' to
+ * the foreign server
+ */
+bool
+is_foreign_pathkey(PlannerInfo *root,
+ RelOptInfo *baserel,
+ PathKey *pathkey)
+{
+ EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
+ PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private;
+ Expr *em_expr;
+
+ /*
+ * is_foreign_expr would detect volatile expressions as well, but checking
+ * ec_has_volatile here saves some cycles.
+ */
+ if (pathkey_ec->ec_has_volatile)
+ return false;
+
+ /* can't push down the sort if the pathkey's opfamily is not shippable */
+ if (!is_shippable(pathkey->pk_opfamily, OperatorFamilyRelationId, fpinfo))
+ return false;
+
+ em_expr = find_em_expr_for_rel(pathkey_ec, baserel);
+ if (em_expr == NULL)
+ return false;
+
+ /*
+ * Finally, determine if it's safe to evaluate the found expr on the
+ * foreign server.
+ */
+ return is_foreign_expr(root, baserel, em_expr);
+}
+
/*
* 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
@@ -3331,6 +3371,45 @@ deparseAggref(Aggref *node, deparse_expr_cxt *context)
appendStringInfoChar(buf, ')');
}
+/*
+ * Append the ASC, DESC, USING <OPERATOR> and NULLS FIRST / NULLS LAST part
+ * of the ORDER BY clause
+ */
+static void
+appendOrderBySuffix(Oid sortop, Oid sortcoltype, bool nulls_first,
+ 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);
+ }
+
+ if (nulls_first)
+ appendStringInfoString(buf, " NULLS FIRST");
+ else
+ appendStringInfoString(buf, " NULLS LAST");
+}
+
/*
* Append ORDER BY within aggregate function.
*/
@@ -3346,7 +3425,6 @@ appendAggOrderBy(List *orderList, List *targetList, deparse_expr_cxt *context)
SortGroupClause *srt = (SortGroupClause *) lfirst(lc);
Node *sortexpr;
Oid sortcoltype;
- TypeCacheEntry *typentry;
if (!first)
appendStringInfoString(buf, ", ");
@@ -3356,32 +3434,8 @@ 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);
- }
-
- if (srt->nulls_first)
- appendStringInfoString(buf, " NULLS FIRST");
- else
- appendStringInfoString(buf, " NULLS LAST");
+ appendOrderBySuffix(srt->sortop, sortcoltype, srt->nulls_first,
+ context);
}
}
@@ -3486,7 +3540,11 @@ 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)
{
@@ -3494,26 +3552,44 @@ 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),
+ ObjectIdGetDatum(em->em_datatype),
+ ObjectIdGetDatum(em->em_datatype),
+ Int16GetDatum(pathkey->pk_strategy));
+
+ if (!HeapTupleIsValid(tuple))
+ elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
+ pathkey->pk_strategy, em->em_datatype, em->em_datatype,
+ pathkey->pk_opfamily);
- Assert(em_expr != NULL);
+ oprid = DatumGetObjectId(SysCacheGetAttr(AMOPSTRATEGY, tuple,
+ Anum_pg_amop_amopopr, &isNull));
+ ReleaseSysCache(tuple);
appendStringInfoString(buf, delim);
deparseExpr(em_expr, context);
- if (pathkey->pk_strategy == BTLessStrategyNumber)
- appendStringInfoString(buf, " ASC");
- else
- appendStringInfoString(buf, " DESC");
- if (pathkey->pk_nulls_first)
- appendStringInfoString(buf, " NULLS FIRST");
- else
- appendStringInfoString(buf, " NULLS LAST");
+ /*
+ * Here we need to use the expression type to compare against the
+ * default btree sort operator.
+ */
+ appendOrderBySuffix(oprid, exprType((Node *) em_expr),
+ pathkey->pk_nulls_first, context);
delim = ", ";
}
diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index e3ee30f1aa..1f44c365ef 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -3258,6 +3258,19 @@ 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)
+-- Ensure that we don't push down an ORDER BY with a non-shippable operator
+explain (verbose, costs off)
+select * from ft2 order by c1 using operator(public.<^);
+ QUERY PLAN
+-------------------------------------------------------------------------------
+ Sort
+ Output: c1, c2, c3, c4, c5, c6, c7, c8
+ Sort Key: ft2.c1 USING <^
+ -> Foreign Scan on public.ft2
+ 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
@@ -3285,6 +3298,16 @@ 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)
+-- Ensure that the ORDER BY is pushed to the foreign server
+explain (verbose, costs off)
+select * from ft2 order by c1 using operator(public.<^);
+ QUERY PLAN
+-----------------------------------------------------------------------------------------------------------------------------
+ Foreign Scan on public.ft2
+ 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 4bdab30a73..1dd4779185 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -917,8 +917,6 @@ 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
@@ -926,13 +924,8 @@ get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel)
* getting it to be sorted by all of those pathkeys. We'll just
* end up resorting the entire data set. So, unless we can push
* down all of the query pathkeys, forget it.
- *
- * 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;
@@ -6540,9 +6533,9 @@ 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,
- pathkey_ec,
- input_rel->reltarget);
+ sort_expr = find_em_for_input_target(root,
+ pathkey_ec,
+ 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))
@@ -7332,13 +7325,12 @@ conversion_error_callback(void *arg)
}
/*
- * Find an equivalence class member expression to be computed as a sort column
- * in the given target.
+ * 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,
- EquivalenceClass *ec,
- PathTarget *target)
+EquivalenceMember *
+find_em_for_input_target(PlannerInfo *root, EquivalenceClass *ec,
+ PathTarget *target)
{
ListCell *lc1;
int i;
@@ -7383,7 +7375,7 @@ 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 ca83306af9..9930226b6f 100644
--- a/contrib/postgres_fdw/postgres_fdw.h
+++ b/contrib/postgres_fdw/postgres_fdw.h
@@ -171,6 +171,9 @@ extern bool is_foreign_expr(PlannerInfo *root,
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,
@@ -213,10 +216,10 @@ 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,
- EquivalenceClass *ec,
- PathTarget *target);
+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);
extern void deparseSelectStmtForRel(StringInfo buf, PlannerInfo *root,
RelOptInfo *foreignrel, List *tlist,
diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql
index 30b5175da5..1bbe1212c4 100644
--- a/contrib/postgres_fdw/sql/postgres_fdw.sql
+++ b/contrib/postgres_fdw/sql/postgres_fdw.sql
@@ -902,6 +902,10 @@ 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;
+-- Ensure that we don't push down an ORDER BY with a non-shippable operator
+explain (verbose, costs off)
+select * from ft2 order by c1 using operator(public.<^);
+
-- Update local stats on ft2
ANALYZE ft2;
@@ -919,6 +923,10 @@ 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;
+-- Ensure that the ORDER BY is pushed to the foreign server
+explain (verbose, costs off)
+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..b367f18eab 100644
--- a/src/backend/optimizer/path/equivclass.c
+++ b/src/backend/optimizer/path/equivclass.c
@@ -932,11 +932,11 @@ is_exprlist_member(Expr *node, List *exprs)
}
/*
- * Find an equivalence class member expression, all of whose Vars, come from
- * the indicated relation.
+ * Find an equivalence class member, 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 +960,22 @@ find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
return NULL;
}
+/*
+ * 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 *em = find_em_for_rel(ec, rel);
+
+ if (em != NULL)
+ return em->em_expr;
+
+ return 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..5a2bbc87e1 100644
--- a/src/include/optimizer/paths.h
+++ b/src/include/optimizer/paths.h
@@ -144,6 +144,8 @@ 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);
--
2.33.0
