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Re: Materialized views WIP patch

From: "Kevin Grittner" <kgrittn(at)mail(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Marko Tiikkaja" <pgmail(at)joh(dot)to>,"Pgsql Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Materialized views WIP patch
Date: 2013-01-16 16:48:17
Message-ID: 20130116164817.97290@gmx.com (view raw or flat)
Thread:
Lists: pgsql-committerspgsql-hackers
Tom Lane wrote:
> "Kevin Grittner" <kgrittn(at)mail(dot)com> writes:
>> I've been struggling with two areas:
>> - pg_dump sorting for MVs which depend on other MVs
> 
> Surely that should fall out automatically given that the
> dependency is properly expressed in pg_depend?
> 
> If you mean you're trying to get it to cope with circular
> dependencies between MVs, it might take some work on the pg_dump
> side, but plain ordering shouldn't require new code.

The *definitions* sort properly, but what I'm trying to do is
define them WITH NO DATA and load data after all the COPY
statements for tables. If mva is referenced by mvb, the goal is the
REFRESH mva, build its indexes before running REFRESH for mvb and
building its indexes. To do things in any other order does't seem
to me to leave things after restore in the same state they were in
at the time of the dump.

So I should have been a little more verbose describing the problem:
pg_dump sorting of REFRESH and CREATE INDEX steps for MVs which
depend on other MVs.

Last night I found why my previous attempts had been failing -- I
was trying to build the dependencies at the wrong point in the dump
process, after the sorts had already been done.  Now that I've
spotted that fundamental flaw, I think I can get this out of the
way without too much more fanfare. I kept thinking I had something
wrong in the detail of my approach, while the problem was at a much
higher level.

Where I really need someone to hit me upside the head with a
clue-stick is the code I added to the bottom of RelationBuildDesc()
in relcache.c. The idea is that on first access to an unlogged MV,
to detect that the heap has been replaced by the init fork, set
relisvalid to false, and make the heap look normal again. I
couldn't see any way to do that which wasn't a kludge, and I can't
figure out how to deal with relcache properly in implementing that
kludge. Either a tip about the right way to work the kludge, or a
suggestion for a less kludgy alternative would be welcome.

-Kevin


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