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 --- src/backend/optimizer/util/pathnode.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'src/backend/optimizer/util/pathnode.c') diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c index f995a86e85c..7656905da85 100644 --- a/src/backend/optimizer/util/pathnode.c +++ b/src/backend/optimizer/util/pathnode.c @@ -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; -- cgit v1.2.3