On Wed, Aug 29, 2018 at 5:06 AM, Amit Langote
<Langote_Amit_f8@lab.ntt.co.jp> wrote:
> It is more or less well known that the planner doesn't perform well with
> more than a few hundred partitions even when only a handful of partitions
> are ultimately included in the plan. Situation has improved a bit in PG
> 11 where we replaced the older method of pruning partitions one-by-one
> using constraint exclusion with a much faster method that finds relevant
> partitions by using partitioning metadata. However, we could only use it
> for SELECT queries, because UPDATE/DELETE are handled by a completely
> different code path, whose structure doesn't allow it to call the new
> pruning module's functionality. Actually, not being able to use the new
> pruning is not the only problem for UPDATE/DELETE, more on which further
> below.
This was a big problem for the SQL MERGE patch. I hope that this
problem can be fixed.
--
Peter Geoghegan