Thread: pgsql: Correctly re-use hash tables in buildSubPlanHash().
Correctly re-use hash tables in buildSubPlanHash(). Commit 356687bd8 omitted to remove leftover code for destroying a hashed subplan's hash tables, with the result that the tables were always rebuilt not reused; this leads to severe memory leakage if a hashed subplan is re-executed enough times. Moreover, the code for reusing the hashnulls table had a typo that would have made it do the wrong thing if it were reached. Looking at the code coverage report shows severe under-coverage of the potential callers of ResetTupleHashTable, so add some test cases that exercise them. Andreas Karlsson and Tom Lane, per reports from Ranier Vilela and Justin Pryzby. Backpatch to v11, as the faulty commit was. Discussion: https://postgr.es/m/edb62547-c453-c35b-3ed6-a069e4d6b937@proxel.se Discussion: https://postgr.es/m/CAEudQAo=DCebm1RXtig9OH+QivpS97sMkikt0A9qHmMUs+g6ZA@mail.gmail.com Discussion: https://postgr.es/m/20200210032547.GA1412@telsasoft.com Branch ------ REL_12_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/96d783ae55b9406f1b5e689e1e7afe8d21e3a549 Modified Files -------------- src/backend/executor/nodeSubplan.c | 6 +- src/test/regress/expected/subselect.out | 123 ++++++++++++++++++++++++++++++++ src/test/regress/sql/subselect.sql | 65 +++++++++++++++++ 3 files changed, 191 insertions(+), 3 deletions(-)