Simon Riggs wrote:
Patch works, but there's a bit I haven't finished yet - checking unique

Did plan invalidation make it safe to rely on the presence of a unique index for planning decisions?

Couldn't we also do join removal for inner joins, when there's a foreign key reference that enforces that there's one and only one matching tuple in the removed table:

SELECT FROM child, parent WHERE child.fkey = parent.pkey


+       /*
+        * We can now remove join by pulling up child plan from the keeprel.
+        * This needs to be done considering costs, since its possible for
+        * a nested inner indexscan plan to be cheaper. So it isn't
+        * always desirable to remove the join.

Can you elaborate that a bit? I can't imagine a case where we wouldn't want to remove a join, when we know we can.

  Heikki Linnakangas

Sent via pgsql-patches mailing list (
To make changes to your subscription:

Reply via email to