Horton

Re: ALTER tbl rewrite loses CLUSTER ON index (consider moving indisclustered to pg_class)

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Amit Langote <amitlangote09@gmail.com>, pgsql-hackers@postgresql.org
Date: 2020-02-07T14:39:35Z
Lists: pgsql-hackers

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On Thu, Feb 06, 2020 at 02:24:47PM -0300, Alvaro Herrera wrote:
> On 2020-Feb-06, Justin Pryzby wrote:
> 
> > I wondered if it wouldn't be better if CLUSTER ON was stored in pg_class as the
> > Oid of a clustered index, rather than a boolean in pg_index.
> 
> Maybe.  Do you want to try a patch?

I think the attached is 80% complete (I didn't touch pg_dump).

One objection to this change would be that all relations (including indices)
end up with relclustered fields, and pg_index already has a number of bools, so
it's not like this one bool is wasting a byte.

I think relisclustered was a's clever way of avoiding that overhead (c0ad5953).
So I would be -0.5 on moving it to pg_class..

But I think 0001 and 0002 are worthy.  Maybe the test in 0002 should live
somewhere else.

Commits

  1. Refactor cluster.c to use new routine get_index_isclustered()

  2. Preserve clustered index after rewrites with ALTER TABLE

  3. Preserve replica identity index across ALTER TABLE rewrite

  4. Remove RangeIOData->typiofunc

  5. Preserve pg_index.indisclustered across REINDEX CONCURRENTLY