Re: Allowing ALTER TYPE to change storage strategy

From: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Allowing ALTER TYPE to change storage strategy
Date: 2020-03-06 13:42:18
Message-ID: 20200306134218.rgcaddnbcudcu5hm@development
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On Thu, Mar 05, 2020 at 05:46:44PM -0500, Tom Lane wrote:
>I wrote:
>> If not, we probably should bite the bullet and go for #1, since
>> I have little doubt that we'll need that someday anyway.
>> The trick will be to keep down the cache invalidation overhead...
>Here's a version that does it like that. I'm less worried about the
>overhead than I was before, because I realized that we already had
>a syscache callback for pg_type there. And it was being pretty
>stupid about which entries it reset, too, so this version might
>actually net out as less overhead (in some workloads anyway).
>For ease of review I just added the new TCFLAGS value out of
>sequence, but I'd be inclined to renumber the bits back into
>sequence before committing.

LGTM. If I had to nitpick, I'd say that the example in docs should be

SEND = mytypesend,
RECEIVE = mytyperecv

i.e. with uppercase SEND/RECEIVE, because that's how we spell it in
other examples in CREATE TYPE etc.


Tomas Vondra
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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