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, 27 insertions, 0 deletions

diff --git a/src/backend/nodes/queryjumblefuncs.c b/src/backend/nodes/queryjumblefuncs.c
index be823a7f8fa..de29d51c631 100644
--- a/src/backend/nodes/queryjumblefuncs.c
+++ b/src/backend/nodes/queryjumblefuncs.c
@@ -141,6 +141,33 @@ JumbleQuery(Query *query)
 	return jstate;
 }
 
+JumbleState *
+JumbleExpr(Expr *expr, uint64 *exprId)
+{
+	JumbleState *jstate = NULL;
+
+	Assert(exprId != NULL);
+
+	jstate = (JumbleState *) palloc(sizeof(JumbleState));
+
+	/* Set up workspace for query jumbling */
+	jstate->jumble = (unsigned char *) palloc(JUMBLE_SIZE);
+	jstate->jumble_len = 0;
+	jstate->clocations_buf_size = 32;
+	jstate->clocations = (LocationLen *)
+		palloc(jstate->clocations_buf_size * sizeof(LocationLen));
+	jstate->clocations_count = 0;
+	jstate->highest_extern_param_id = 0;
+
+	/* Compute query ID */
+	_jumbleNode(jstate, (Node *) expr);
+	*exprId = DatumGetUInt64(hash_any_extended(jstate->jumble,
+											   jstate->jumble_len,
+											   0));
+
+	return jstate;
+}
+
 /*
  * Enables query identifier computation.
  *