Re: UPDATE of partition key

On 13 July 2017 at 22:39, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com> wrote:
> Attached is a WIP patch (make_resultrels_ordered.patch) that generates
> the result rels in canonical order. This patch is kept separate from
> the update-partition-key patch, and can be applied on master branch.

Attached update-partition-key_v13.patch now contains this
make_resultrels_ordered.patch changes.

So now that the per-subplan result rels and the leaf partition oids
that are generated for tuple routing are both known to have the same
order (cannonical), in ExecSetupPartitionTupleRouting(), we look for
the per-subplan results without the need for a hash table. Instead of
the hash table, we iterate over the leaf partition oids and at the
same time keep shifting a position over the per-subplan resultrels
whenever the resultrel at the position is found to be present in the
leaf partitions list. Since the two lists are in the same order, we
never have to again scan the portition of the lists that is already
scanned.

I considered whether the issue behind this recent commit might be
relevant for update tuple-routing as well :
commit f81a91db4d1c2032632aa5df9fc14be24f5fe5ec
Author: Robert Haas <rhaas(at)postgresql(dot)org>
Date: Mon Jul 17 21:29:45 2017 -0400
Use a real RT index when setting up partition tuple routing.

Since we know that using a dummy 1 value for tuple routing result rels
is not correct, I am checking about another possibility : Now in the
latest patch, the tuple routing partitions would have a mix of a)
existing update result-rels, and b) new partition resultrels. 'b'
resultrels would have the RT index of nominalRelation, but the
existing 'a' resultrels would have their own different RT indexes. I
suspect, this might surface a similar issue that was fixed by the
above commit, for e.g. with the WITH query having UPDATE subqueries
doing tuple routing. Will check that.

This patch also has Robert's changes in the planner to decide whether
to do update tuple routing.

--
Thanks,
-Amit Khandekar
EnterpriseDB Corporation
The Postgres Database Company