Re: [HACKERS] UPDATE of partition key - Mailing list pgsql-hackers

From Amit Khandekar
Subject Re: [HACKERS] UPDATE of partition key
Date
Msg-id CAJ3gD9cQ555izUDLpa7vT_3w254+yfXVQWX2XUxygF1PvgynWQ@mail.gmail.com
Whole thread Raw
In response to Re: [HACKERS] UPDATE of partition key  (Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>)
Responses Re: [HACKERS] UPDATE of partition key
List pgsql-hackers
On 29 June 2017 at 07:42, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> wrote:
> Hi Amit,
>
> On 2017/06/28 20:43, Amit Khandekar wrote:
>> In attached patch v12
>
> The patch no longer applies and fails to compile after the following
> commit was made yesterday:
>
> commit 501ed02cf6f4f60c3357775eb07578aebc912d3a
> Author: Andrew Gierth <rhodiumtoad@postgresql.org>
> Date:   Wed Jun 28 18:55:03 2017 +0100
>
>     Fix transition tables for partition/inheritance.

Thanks for informing Amit.

As Thomas mentioned upthread, the above commit already uses a tuple
conversion mapping from leaf partition to root partitioned table
(mt_transition_tupconv_maps), which serves the same purpose as that of
the mapping used in the update-partition-key patch during update tuple
routing (mt_resultrel_maps).

We need to try to merge these two into a general-purpose mapping array
such as mt_leaf_root_maps. I haven't done that in the rebased patch
(attached), so currently it has both these mapping fields.

For transition tables, this map is per-leaf-partition in case of
inserts, whereas it is per-subplan result rel for updates. For
update-tuple routing, the mapping is required to be per-subplan. Now,
for update-row-movement in presence of transition tables, we would
require both per-subplan mapping as well as per-leaf-partition
mapping, which can't be done if we have a single mapping field, unless
we have some way to identify which of the per-leaf partition mapping
elements belong to per-subplan rels.

So, it's not immediately possible to merge them.

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