Re: Declarative partitioning - another take

From: Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
To: Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>
Cc: Amit Langote <amitlangote09(at)gmail(dot)com>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Declarative partitioning - another take
Date: 2016-09-27 08:39:02
Message-ID: 45d2f224-634d-8e50-48c0-8d649a91fcd6@lab.ntt.co.jp
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Sorry about the delay in replying.

On 2016/09/15 21:58, Ashutosh Bapat wrote:
> Hi Amit,
>
> It looks like there is some problem while creating paramterized paths
> for multi-level partitioned tables. Here's a longish testcase
>
> [ ... ]
>
> Please check if you are able to reproduce these errors in your
> repository. I made sure that I cleaned up all partition-wise join code
> before testing this, but ... .

Thanks for the test case. I can reproduce the same.

> I tried to debug the problem somewhat. In set_append_rel_pathlist(),
> it finds that at least one child has a parameterized path as the
> cheapest path, so it doesn't create an unparameterized path for append
> rel. At the same time there is a parameterization common to all the
> children, so it doesn't create any path. There seem to be two problems
> here
> 1. The children from second level onwards may not be getting
> parameterized for lateral references. That seems unlikely but
> possible.
> 2. Reparameterization should have corrected this, but
> reparameterize_path() does not support AppendPaths.

Hmm, 0005-Refactor-optimizer-s-inheritance-set-expansion-code-5.patch is
certainly to be blamed here; if I revert the patch, the problem goes away.

Based on 2 above, I attempted to add logic for AppendPath in
reparameterize_path() as in the attached. It fixes the reported problem
and does not break any regression tests. If it's sane to do things this
way, I will incorporate the attached into patch 0005 mentioned above.
Thoughts?

Thanks,
Amit

Attachment Content-Type Size
reparameterize-append-path.patch text/x-diff 4.8 KB

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