Short-circuit row estimation in NOT IN containing NULL consts ScalarArrayOpExpr used for either NOT IN or <>/= ALL, when the array contains a NULL constant, will never evaluate to true. Here we add an explicit short-circuit in scalararraysel() to account for this and return 0.0 rows when we see that a NULL exists. When the array is a constant, we can very quickly see if there are any NULL values and return early before going to much effort in scalararraysel(). For non-const arrays, we short-circuit after finding the first NULL and forego selectivity estimations of any remaining elements.
In the future, it might be better to do something for this case in constant folding. We would need to be careful to only do this for strict operators on expressions located in places that don't care about distinguishing false from NULL returns. i.e. EXPRKIND_QUAL expressions. Doing that requires a bit more thought and effort, so here we just fix some needlessly slow selectivity estimations for ScalarArrayOpExpr containing many array elements and at least one NULL. Author: Ilia Evdokimov <[email protected]> Reviewed-by: David Geier <[email protected]> Reviewed-by: Zsolt Parragi <[email protected]> Reviewed-by: David Rowley <[email protected]> Discussion: https://postgr.es/m/[email protected] Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/c95cd2991f1e3ece689adfe662082f200126d255 Modified Files -------------- src/backend/utils/adt/selfuncs.c | 17 +++++++++++++++++ src/test/regress/expected/planner_est.out | 27 +++++++++++++++++++++++++++ src/test/regress/sql/planner_est.sql | 15 +++++++++++++++ 3 files changed, 59 insertions(+)
