Thread: pgsql: Fix incorrect handling of join clauses pushed intoparameterized
Fix incorrect handling of join clauses pushed into parameterized paths. In some cases a clause attached to an outer join can be pushed down into the outer join's RHS even though the clause is not degenerate --- this can happen if we choose to make a parameterized path for the RHS. If the clause ends up attached to a lower outer join, we'd misclassify it as being a "join filter" not a plain "filter" condition at that node, leading to wrong query results. To fix, teach extract_actual_join_clauses to examine each join clause's required_relids, not just its is_pushed_down flag. (The latter now seems vestigial, or at least in need of rethinking, but we won't do anything so invasive as redefining it in a bug-fix patch.) This has been wrong since we introduced parameterized paths in 9.2, though it's evidently hard to hit given the lack of previous reports. The test case used here involves a lateral function call, and I think that a lateral reference may be required to get the planner to select a broken plan; though I wouldn't swear to that. In any case, even if LATERAL is needed to trigger the bug, it still affects all supported branches, so back-patch to all. Per report from Andreas Karlsson. Thanks to Andrew Gierth for preliminary investigation. Discussion: https://postgr.es/m/f8128b11-c5bf-3539-48cd-234178b2314d@proxel.se Branch ------ REL9_6_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/0c141fcaa7dd806752986401b25de8f665ceb3fe Modified Files -------------- src/backend/optimizer/plan/createplan.c | 3 +++ src/backend/optimizer/util/restrictinfo.c | 11 ++++++++++- src/include/optimizer/restrictinfo.h | 1 + src/test/regress/expected/join.out | 27 +++++++++++++++++++++++++++ src/test/regress/sql/join.sql | 11 +++++++++++ 5 files changed, 52 insertions(+), 1 deletion(-)
Re: pgsql: Fix incorrect handling of join clauses pushed into parameterized
From
Andrew Dunstan
Date:
On Thu, Apr 19, 2018 at 3:49 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote: > Fix incorrect handling of join clauses pushed into parameterized paths. > > In some cases a clause attached to an outer join can be pushed down into > the outer join's RHS even though the clause is not degenerate --- this > can happen if we choose to make a parameterized path for the RHS. If > the clause ends up attached to a lower outer join, we'd misclassify it > as being a "join filter" not a plain "filter" condition at that node, > leading to wrong query results. > > To fix, teach extract_actual_join_clauses to examine each join clause's > required_relids, not just its is_pushed_down flag. (The latter now > seems vestigial, or at least in need of rethinking, but we won't do > anything so invasive as redefining it in a bug-fix patch.) > > This has been wrong since we introduced parameterized paths in 9.2, > though it's evidently hard to hit given the lack of previous reports. > The test case used here involves a lateral function call, and I think > that a lateral reference may be required to get the planner to select > a broken plan; though I wouldn't swear to that. In any case, even if > LATERAL is needed to trigger the bug, it still affects all supported > branches, so back-patch to all. > > Per report from Andreas Karlsson. Thanks to Andrew Gierth for > preliminary investigation. > > Discussion: https://postgr.es/m/f8128b11-c5bf-3539-48cd-234178b2314d@proxel.se > > Branch > ------ > REL9_6_STABLE > Seems to have broken the buildfarm on 9.6. cheers andrew -- Andrew Dunstan https://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services