Horton

Improve nbtree unsatisfiable RowCompare detection.

Peter Geoghegan <pg@bowt.ie>

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Commit: ec986020decff322723cf7b3a2696803d082ad17
Author: Peter Geoghegan <pg@bowt.ie>
Date: 2025-01-07T15:38:30Z
Releases: 18.0 
Improve nbtree unsatisfiable RowCompare detection.

Move nbtree's detection of RowCompare quals that are unsatisfiable due
to having a NULL in their first row element: rather than detecting these
cases at the point where _bt_first builds its insertion scan key, do so
earlier, during preprocessing proper.  This brings the RowCompare case
in line every other case involving an unsatisfiable-due-to-NULL qual.

nbtree now consistently detects such unsatisfiable quals -- even when
they happen to involve a key that isn't examined by _bt_first at all.
Affected cases thereby avoid useless full index scans that cannot
possibly return any matching rows.

Author: Peter Geoghegan <pg@bowt.ie>
Reviewed-By: Matthias van de Meent <boekewurm+postgres@gmail.com>
Discussion: https://postgr.es/m/CAH2-WzmySVXst2hFrOATC-zw1Byg1XC-jYUS314=mzuqsNwk+Q@mail.gmail.com

Files

PathChange+/−
src/backend/access/nbtree/nbtsearch.c modified +13 −13
src/backend/access/nbtree/nbtutils.c modified +11 −3
src/test/regress/expected/btree_index.out modified +127 −0
src/test/regress/expected/create_index.out modified +13 −0
src/test/regress/sql/btree_index.sql modified +79 −0
src/test/regress/sql/create_index.sql modified +5 −0

Discussion