Re: Patch: Write Amplification Reduction Method (WARM)

From: Andres Freund <andres(at)anarazel(dot)de>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Jaime Casanova <jaime(dot)casanova(at)2ndquadrant(dot)com>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Patch: Write Amplification Reduction Method (WARM)
Date: 2017-01-31 22:51:01
Message-ID: 20170131225101.2l2fft4nnq525lx7@alap3.anarazel.de
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On 2017-01-31 17:21:28 -0500, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > Hm, sorry for missing this earlier. I think CatalogUpdateIndexes() is
> > fairly widely used in extensions - it seems like a pretty harsh change
> > to not leave some backward compatibility layer in place.
>
> If an extension is doing that, it is probably constructing tuples to put
> into the catalog, which means it'd be equally (and much more quietly)
> broken by any change to the catalog's schema. We've never considered
> such an argument as a reason not to change catalog schemas, though.

I know of several extensions that use CatalogUpdateIndexes() to update
their own tables. Citus included (It's trivial to change on our side, so
that's not a reason to do or not do something). There really is no
convenient API to do so without it.

> (I'm a little more concerned by Alvaro's apparent position that WARM
> is a done deal; I didn't think so. This particular change seems like
> good cleanup anyhow, however.)

Yea, I don't think we're even close to that either.

Andres

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