mirror of
https://github.com/postgres/postgres.git
synced 2025-06-13 07:41:39 +03:00
Ensure that foreign scans with lateral refs are planned correctly.
As reported in bug #15613 from Srinivasan S A, file_fdw and postgres_fdw
neglected to mark plain baserel foreign paths as parameterized when the
relation has lateral_relids. Other FDWs have surely copied this mistake,
so rather than just patching those two modules, install a band-aid fix
in create_foreignscan_path to rectify the mistake centrally.
Although the band-aid is enough to fix the visible symptom, correct
the calls in file_fdw and postgres_fdw anyway, so that they are valid
examples for external FDWs.
Also, since the band-aid isn't enough to make this work for parameterized
foreign joins, throw an elog(ERROR) if such a case is passed to
create_foreignscan_path. This shouldn't pose much of a problem for
existing external FDWs, since it's likely they aren't trying to make such
paths anyway (though some of them may need a defense against joins with
lateral_relids, similar to the one this patch installs into postgres_fdw).
Add some assertions in relnode.c to catch future occurrences of the same
error --- in particular, as backstop against core-code mistakes like the
one fixed by commit bdd9a99aa.
Discussion: https://postgr.es/m/15613-092be1be9576c728@postgresql.org
This commit is contained in:
Tom Lane
@ -521,6 +521,10 @@ fileGetForeignPaths(PlannerInfo *root,
|
||||
* Create a ForeignPath node and add it as only possible path. We use the
|
||||
* fdw_private list of the path to carry the convert_selectively option;
|
||||
* it will be propagated into the fdw_private list of the Plan node.
|
||||
*
|
||||
* We don't support pushing join clauses into the quals of this path, but
|
||||
* it could still have required parameterization due to LATERAL refs in
|
||||
* its tlist.
|
||||
*/
|
||||
add_path(baserel, (Path *)
|
||||
create_foreignscan_path(root, baserel,
|
||||
@ -529,7 +533,7 @@ fileGetForeignPaths(PlannerInfo *root,
|
||||
startup_cost,
|
||||
total_cost,
|
||||
NIL, /* no pathkeys */
|
||||
NULL, /* no outer rel either */
|
||||
baserel->lateral_relids,
|
||||
NULL, /* no extra plan */
|
||||
coptions));
|
||||
|
||||
|
||||
@ -2132,6 +2132,62 @@ SELECT t1."C 1" FROM "S 1"."T 1" t1, LATERAL (SELECT DISTINCT t2.c1, t3.c1 FROM
|
||||
1
|
||||
(10 rows)
|
||||
|
||||
-- bug #15613: bad plan for foreign table scan with lateral reference
|
||||
EXPLAIN (VERBOSE, COSTS OFF)
|
||||
SELECT ref_0.c2, subq_1.*
|
||||
FROM
|
||||
"S 1"."T 1" AS ref_0,
|
||||
LATERAL (
|
||||
SELECT ref_0."C 1" c1, subq_0.*
|
||||
FROM (SELECT ref_0.c2, ref_1.c3
|
||||
FROM ft1 AS ref_1) AS subq_0
|
||||
RIGHT JOIN ft2 AS ref_3 ON (subq_0.c3 = ref_3.c3)
|
||||
) AS subq_1
|
||||
WHERE ref_0."C 1" < 10 AND subq_1.c3 = '00001'
|
||||
ORDER BY ref_0."C 1";
|
||||
QUERY PLAN
|
||||
---------------------------------------------------------------------------------------------------------
|
||||
Nested Loop
|
||||
Output: ref_0.c2, ref_0."C 1", (ref_0.c2), ref_1.c3, ref_0."C 1"
|
||||
-> Nested Loop
|
||||
Output: ref_0.c2, ref_0."C 1", ref_1.c3, (ref_0.c2)
|
||||
-> Index Scan using t1_pkey on "S 1"."T 1" ref_0
|
||||
Output: ref_0."C 1", ref_0.c2, ref_0.c3, ref_0.c4, ref_0.c5, ref_0.c6, ref_0.c7, ref_0.c8
|
||||
Index Cond: (ref_0."C 1" < 10)
|
||||
-> Foreign Scan on public.ft1 ref_1
|
||||
Output: ref_1.c3, ref_0.c2
|
||||
Remote SQL: SELECT c3 FROM "S 1"."T 1" WHERE ((c3 = '00001'::text))
|
||||
-> Materialize
|
||||
Output: ref_3.c3
|
||||
-> Foreign Scan on public.ft2 ref_3
|
||||
Output: ref_3.c3
|
||||
Remote SQL: SELECT c3 FROM "S 1"."T 1" WHERE ((c3 = '00001'::text))
|
||||
(15 rows)
|
||||
|
||||
SELECT ref_0.c2, subq_1.*
|
||||
FROM
|
||||
"S 1"."T 1" AS ref_0,
|
||||
LATERAL (
|
||||
SELECT ref_0."C 1" c1, subq_0.*
|
||||
FROM (SELECT ref_0.c2, ref_1.c3
|
||||
FROM ft1 AS ref_1) AS subq_0
|
||||
RIGHT JOIN ft2 AS ref_3 ON (subq_0.c3 = ref_3.c3)
|
||||
) AS subq_1
|
||||
WHERE ref_0."C 1" < 10 AND subq_1.c3 = '00001'
|
||||
ORDER BY ref_0."C 1";
|
||||
c2 | c1 | c2 | c3
|
||||
----+----+----+-------
|
||||
1 | 1 | 1 | 00001
|
||||
2 | 2 | 2 | 00001
|
||||
3 | 3 | 3 | 00001
|
||||
4 | 4 | 4 | 00001
|
||||
5 | 5 | 5 | 00001
|
||||
6 | 6 | 6 | 00001
|
||||
7 | 7 | 7 | 00001
|
||||
8 | 8 | 8 | 00001
|
||||
9 | 9 | 9 | 00001
|
||||
(9 rows)
|
||||
|
||||
-- non-Var items in targetlist of the nullable rel of a join preventing
|
||||
-- push-down in some cases
|
||||
-- unable to push {ft1, ft2}
|
||||
|
||||
@ -893,6 +893,9 @@ postgresGetForeignPaths(PlannerInfo *root,
|
||||
* baserestrict conditions we were able to send to remote, there might
|
||||
* actually be an indexscan happening there). We already did all the work
|
||||
* to estimate cost and size of this path.
|
||||
*
|
||||
* Although this path uses no join clauses, it could still have required
|
||||
* parameterization due to LATERAL refs in its tlist.
|
||||
*/
|
||||
path = create_foreignscan_path(root, baserel,
|
||||
NULL, /* default pathtarget */
|
||||
@ -900,7 +903,7 @@ postgresGetForeignPaths(PlannerInfo *root,
|
||||
fpinfo->startup_cost,
|
||||
fpinfo->total_cost,
|
||||
NIL, /* no pathkeys */
|
||||
NULL, /* no outer rel either */
|
||||
baserel->lateral_relids,
|
||||
NULL, /* no extra plan */
|
||||
NIL); /* no fdw_private list */
|
||||
add_path(baserel, (Path *) path);
|
||||
@ -4243,7 +4246,7 @@ add_paths_with_pathkeys_for_rel(PlannerInfo *root, RelOptInfo *rel,
|
||||
startup_cost,
|
||||
total_cost,
|
||||
useful_pathkeys,
|
||||
NULL,
|
||||
rel->lateral_relids,
|
||||
sorted_epq_path,
|
||||
NIL));
|
||||
}
|
||||
@ -4276,6 +4279,13 @@ postgresGetForeignJoinPaths(PlannerInfo *root,
|
||||
if (joinrel->fdw_private)
|
||||
return;
|
||||
|
||||
/*
|
||||
* This code does not work for joins with lateral references, since those
|
||||
* must have parameterized paths, which we don't generate yet.
|
||||
*/
|
||||
if (!bms_is_empty(joinrel->lateral_relids))
|
||||
return;
|
||||
|
||||
/*
|
||||
* Create unfinished PgFdwRelationInfo entry which is used to indicate
|
||||
* that the join relation is already considered, so that we won't waste
|
||||
@ -4367,7 +4377,7 @@ postgresGetForeignJoinPaths(PlannerInfo *root,
|
||||
startup_cost,
|
||||
total_cost,
|
||||
NIL, /* no pathkeys */
|
||||
NULL, /* no required_outer */
|
||||
joinrel->lateral_relids,
|
||||
epq_path,
|
||||
NULL); /* no fdw_private */
|
||||
|
||||
|
||||
@ -516,6 +516,32 @@ EXPLAIN (VERBOSE, COSTS OFF)
|
||||
SELECT t1."C 1" FROM "S 1"."T 1" t1, LATERAL (SELECT DISTINCT t2.c1, t3.c1 FROM ft1 t2, ft2 t3 WHERE t2.c1 = t3.c1 AND t2.c2 = t1.c2) q ORDER BY t1."C 1" OFFSET 10 LIMIT 10;
|
||||
SELECT t1."C 1" FROM "S 1"."T 1" t1, LATERAL (SELECT DISTINCT t2.c1, t3.c1 FROM ft1 t2, ft2 t3 WHERE t2.c1 = t3.c1 AND t2.c2 = t1.c2) q ORDER BY t1."C 1" OFFSET 10 LIMIT 10;
|
||||
|
||||
-- bug #15613: bad plan for foreign table scan with lateral reference
|
||||
EXPLAIN (VERBOSE, COSTS OFF)
|
||||
SELECT ref_0.c2, subq_1.*
|
||||
FROM
|
||||
"S 1"."T 1" AS ref_0,
|
||||
LATERAL (
|
||||
SELECT ref_0."C 1" c1, subq_0.*
|
||||
FROM (SELECT ref_0.c2, ref_1.c3
|
||||
FROM ft1 AS ref_1) AS subq_0
|
||||
RIGHT JOIN ft2 AS ref_3 ON (subq_0.c3 = ref_3.c3)
|
||||
) AS subq_1
|
||||
WHERE ref_0."C 1" < 10 AND subq_1.c3 = '00001'
|
||||
ORDER BY ref_0."C 1";
|
||||
|
||||
SELECT ref_0.c2, subq_1.*
|
||||
FROM
|
||||
"S 1"."T 1" AS ref_0,
|
||||
LATERAL (
|
||||
SELECT ref_0."C 1" c1, subq_0.*
|
||||
FROM (SELECT ref_0.c2, ref_1.c3
|
||||
FROM ft1 AS ref_1) AS subq_0
|
||||
RIGHT JOIN ft2 AS ref_3 ON (subq_0.c3 = ref_3.c3)
|
||||
) AS subq_1
|
||||
WHERE ref_0."C 1" < 10 AND subq_1.c3 = '00001'
|
||||
ORDER BY ref_0."C 1";
|
||||
|
||||
-- non-Var items in targetlist of the nullable rel of a join preventing
|
||||
-- push-down in some cases
|
||||
-- unable to push {ft1, ft2}
|
||||
|
||||
@ -1855,6 +1855,29 @@ create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel,
|
||||
{
|
||||
ForeignPath *pathnode = makeNode(ForeignPath);
|
||||
|
||||
/*
|
||||
* Since the path's required_outer should always include all the rel's
|
||||
* lateral_relids, forcibly add those if necessary. This is a bit of a
|
||||
* hack, but up till early 2019 the contrib FDWs failed to ensure that,
|
||||
* and it's likely that the same error has propagated into many external
|
||||
* FDWs. Don't risk modifying the passed-in relid set here.
|
||||
*/
|
||||
if (rel->lateral_relids && !bms_is_subset(rel->lateral_relids,
|
||||
required_outer))
|
||||
required_outer = bms_union(required_outer, rel->lateral_relids);
|
||||
|
||||
/*
|
||||
* Although this function is only designed to be used for scans of
|
||||
* baserels, before v12 postgres_fdw abused it to make paths for join and
|
||||
* upper rels. It will work for such cases as long as required_outer is
|
||||
* empty (otherwise get_baserel_parampathinfo does the wrong thing), which
|
||||
* fortunately is the expected case for now.
|
||||
*/
|
||||
if (!bms_is_empty(required_outer) &&
|
||||
!(rel->reloptkind == RELOPT_BASEREL ||
|
||||
rel->reloptkind == RELOPT_OTHER_MEMBER_REL))
|
||||
elog(ERROR, "parameterized foreign joins are not supported yet");
|
||||
|
||||
pathnode->path.pathtype = T_ForeignScan;
|
||||
pathnode->path.parent = rel;
|
||||
pathnode->path.pathtarget = target ? target : rel->reltarget;
|
||||
|
||||
@ -1002,6 +1002,9 @@ get_baserel_parampathinfo(PlannerInfo *root, RelOptInfo *baserel,
|
||||
double rows;
|
||||
ListCell *lc;
|
||||
|
||||
/* If rel has LATERAL refs, every path for it should account for them */
|
||||
Assert(bms_is_subset(baserel->lateral_relids, required_outer));
|
||||
|
||||
/* Unparameterized paths have no ParamPathInfo */
|
||||
if (bms_is_empty(required_outer))
|
||||
return NULL;
|
||||
@ -1101,6 +1104,9 @@ get_joinrel_parampathinfo(PlannerInfo *root, RelOptInfo *joinrel,
|
||||
double rows;
|
||||
ListCell *lc;
|
||||
|
||||
/* If rel has LATERAL refs, every path for it should account for them */
|
||||
Assert(bms_is_subset(joinrel->lateral_relids, required_outer));
|
||||
|
||||
/* Unparameterized paths have no ParamPathInfo or extra join clauses */
|
||||
if (bms_is_empty(required_outer))
|
||||
return NULL;
|
||||
@ -1297,6 +1303,9 @@ get_appendrel_parampathinfo(RelOptInfo *appendrel, Relids required_outer)
|
||||
ParamPathInfo *ppi;
|
||||
ListCell *lc;
|
||||
|
||||
/* If rel has LATERAL refs, every path for it should account for them */
|
||||
Assert(bms_is_subset(appendrel->lateral_relids, required_outer));
|
||||
|
||||
/* Unparameterized paths have no ParamPathInfo */
|
||||
if (bms_is_empty(required_outer))
|
||||
return NULL;
|
||||
|
||||
Reference in New Issue
Block a user