Allow Memoize to operate in binary comparison mode

Enterprise / PostgreSQL - David Rowley [postgresql.org] - 23 November 2021 21:06 UTC

Memoize would always use the hash equality operator for the cache key types to determine if the current set of parameters were the same as some previously cached set. Certain types such as floating points where -0.0 and +0.0 differ in their binary representation but are classed as equal by the hash equality operator may cause problems as unless the join uses the same operator it's possible that whichever join operator is being used would be able to distinguish the two values. In which case we may accidentally return in the incorrect rows out of the cache.

To fix this here we add a binary mode to Memoize to allow it to the current set of parameters to previously cached values by comparing bit-by-bit rather than logically using the hash equality operator. This binary mode is always used for LATERAL joins and it's used for normal joins when any of the join operators are not hashable.

e502150f7d Allow Memoize to operate in binary comparison mode
contrib/postgres_fdw/expected/postgres_fdw.out | 3 +-
src/backend/commands/explain.c | 3 +
src/backend/executor/nodeMemoize.c | 92 ++++++++++++++++++++-----
src/backend/nodes/copyfuncs.c | 1 +
src/backend/nodes/outfuncs.c | 2 +
src/backend/nodes/readfuncs.c | 1 +
src/backend/optimizer/path/joinpath.c | 38 +++++++++--
src/backend/optimizer/plan/createplan.c | 10 ++-
src/backend/optimizer/util/pathnode.c | 4 +-
src/backend/utils/adt/datum.c | 52 ++++++++++++++
src/include/nodes/execnodes.h | 2 +
src/include/nodes/pathnodes.h | 2 +
src/include/nodes/plannodes.h | 2 +
src/include/optimizer/pathnode.h | 1 +
src/include/utils/datum.h | 8 +++
src/test/regress/expected/join.out | 28 +++++---
src/test/regress/expected/memoize.out | 93 ++++++++++++++++++++++++--
src/test/regress/expected/subselect.out | 3 +-
src/test/regress/sql/memoize.sql | 39 +++++++++++
19 files changed, 345 insertions(+), 39 deletions(-)

Upstream: git.postgresql.org


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