On 24/7/2024 15:22, Ashutosh Bapat wrote:
On Wed, Jul 24, 2024 at 9:42 AM Richard Guo <guofengli...@gmail.com> wrote:
Is there a specific query that demonstrates benefits from this change?
I'm curious about scenarios where a partitionwise join runs slower
than a non-partitionwise join.
[1] provides a testcase where a nonpartitionwise join is better than
partitionwise join. This testcase is derived from a bug reported by an
EDB customer. [2] is another bug report on psql-bugs.
I haven't passed through the patch yet, but can this issue affect the
decision on what to push down to foreign servers: a whole join or just a
scan of two partitions?
If the patch is related to the pushdown decision, I'd say it is quite an
annoying problem for me. From time to time, I see cases where JOIN
produces more tuples than both partitions have in total - in this case,
it would be better to transfer tables' tuples to the main instance
before joining them.
--
regards, Andrei Lepikhov
