From d468da0d65905b762dbaa647aaf8ba1ea5bca04d Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 7 Feb 2019 13:10:46 -0500 Subject: 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 --- contrib/postgres_fdw/expected/postgres_fdw.out | 56 ++++++++++++++++++++++++++ contrib/postgres_fdw/postgres_fdw.c | 16 ++++++-- contrib/postgres_fdw/sql/postgres_fdw.sql | 26 ++++++++++++ 3 files changed, 95 insertions(+), 3 deletions(-) (limited to 'contrib/postgres_fdw') diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index de4a1b6df86..020350fb379 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -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} diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index 309f27ca856..1326fcf8226 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -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 */ diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index 3e488e0ebe4..e424ebbe1d8 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -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} -- cgit v1.2.3