postgrespro.git / summary / log / commit / refs

commit    fa86238f1eac5b1bfb3887d2deb138f53da82c9b
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Thu Feb 21 01:53:08 2019 +0000

    Speed up match_eclasses_to_foreign_key_col() when there are many ECs.
    
    Check ec_relids before bothering to iterate through the EC members.
    On a perhaps extreme, but still real-world, query in which
    match_eclasses_to_foreign_key_col() accounts for the bulk of the
    planner's runtime, this saves nearly 40% of the runtime.  It's a bit
    of a stopgap fix, but it's simple enough to be back-patched to 9.6
    where this code came in; so let's do that.
    
    David Rowley
    
    Discussion: https://postgr.es/m/6970.1545327857@sss.pgh.pa.us


 src/backend/optimizer/path/equivclass.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c
index 23792508b7..61b5b119b0 100644
--- a/src/backend/optimizer/path/equivclass.c
+++ b/src/backend/optimizer/path/equivclass.c
@@ -2052,6 +2052,14 @@ match_eclasses_to_foreign_key_col(PlannerInfo *root,
 			continue;
 		/* Note: it seems okay to match to "broken" eclasses here */
 
+		/*
+		 * If eclass visibly doesn't have members for both rels, there's no
+		 * need to grovel through the members.
+		 */
+		if (!bms_is_member(var1varno, ec->ec_relids) ||
+			!bms_is_member(var2varno, ec->ec_relids))
+			continue;
+
 		foreach(lc2, ec->ec_members)
 		{
 			EquivalenceMember *em = (EquivalenceMember *) lfirst(lc2);


[parent: d26a810ebf9e]