Re: UPDATE of partition key

On Fri, Jun 30, 2017 at 12:01 AM, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com> wrote:
> On 29 June 2017 at 07:42, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)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(at)postgresql(dot)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.

Would make sense to have a set of functions with names like
GetConvertor{From,To}{Subplan,Leaf}(mtstate, index) which build arrays
m_convertors_{from,to}_by_{subplan,leaf} the first time they need
them?

--
Thomas Munro
http://www.enterprisedb.com