Improve statistics estimation for single-column GROUP BY in sub-queries This commit follows the idea of the 4767bc8ff2. If sub-query has only one GROUP BY column, we can consider its output variable as being unique. We can employ this fact in the statistics to make more precise estimations in the upper query block.
Author: Andrei Lepikhov <lepi...@gmail.com> Reviewed-by: Heikki Linnakangas <hlinn...@iki.fi> Reviewed-by: Alexander Korotkov <aekorot...@gmail.com> Branch ------ master Details ------- https://git.postgresql.org/pg/commitdiff/e983ee9380fcac746f9b6b7c360d255d9fcd0907 Modified Files -------------- src/backend/utils/adt/selfuncs.c | 53 +++++++++++++++++++-------------- src/include/utils/selfuncs.h | 3 +- src/test/regress/expected/stats_ext.out | 15 ++++++++++ src/test/regress/sql/stats_ext.sql | 12 ++++++++ 4 files changed, 60 insertions(+), 23 deletions(-)
