Fix calculation in brin_minmax_multi_distance_date When calculating the distance between date values, make sure to subtract them in the right order, i.e. (larger - smaller).
The distance is used to determine which values to merge, and is expected to be a positive value. The code unfortunately did the subtraction in the opposite order, i.e. (smaller - larger), thus producing negative values and merging values the most distant values first. The resulting index is correct (i.e. produces correct results), but may be significantly less efficient. This affects all minmax-multi indexes on date columns. Backpatch to 14, where minmax-multi indexes were introduced. Reported-by: Ashutosh Bapat Reviewed-by: Ashutosh Bapat, Dean Rasheed Backpatch-through: 14 Discussion: https://postgr.es/m/eef0ea8c-4aaa-8d0d-027f-58b1f35dd...@enterprisedb.com Branch ------ REL_16_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/e7965226d5518796cb2c1a48635ae92b5fe4e6ef Modified Files -------------- src/backend/access/brin/brin_minmax_multi.c | 7 ++++++- src/test/regress/expected/brin_multi.out | 20 ++++++++++++++++++++ src/test/regress/sql/brin_multi.sql | 18 ++++++++++++++++++ 3 files changed, 44 insertions(+), 1 deletion(-)