Transform OR clauses to ANY expression

Replace (expr op C1) OR (expr op C2) ... with expr op ANY(ARRAY[C1, C2, ...])
on the preliminary stage of optimization when we are still working with the
expression tree.

Here Cn is a n-th constant expression, 'expr' is non-constant expression, 'op'
is an operator which returns boolean result and has a commuter (for the case
of reverse order of constant and non-constant parts of the expression,
like 'Cn op expr').

Sometimes it can lead to not optimal plan.  This is why there is a
or_to_any_transform_limit GUC.  It specifies a threshold value of length of
arguments in an OR expression that triggers the OR-to-ANY transformation.
Generally, more groupable OR arguments mean that transformation will be more
likely to win than to lose.

Discussion: https://postgr.es/m/567ED6CA.2040504%40sigaev.ru
Author: Alena Rybakina <lena.ribackina@yandex.ru>
Author: Andrey Lepikhov <a.lepikhov@postgrespro.ru>
Reviewed-by: Peter Geoghegan <pg@bowt.ie>
Reviewed-by: Ranier Vilela <ranier.vf@gmail.com>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Jian He <jian.universality@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/include/optimizer/optimizer.h b/src/include/optimizer/optimizer.h
index 7b63c5cf718..960dfb97a38 100644
--- a/src/include/optimizer/optimizer.h
+++ b/src/include/optimizer/optimizer.h
@@ -133,6 +133,8 @@ extern void extract_query_dependencies(Node *query,
 
 /* in prep/prepqual.c: */
 
+extern PGDLLIMPORT int or_to_any_transform_limit;
+
 extern Node *negate_clause(Node *node);
 extern Expr *canonicalize_qual(Expr *qual, bool is_check);