Re: Why are we PageInit'ing buffers in RelationAddExtraBlocks()?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Andres Freund <andres(at)anarazel(dot)de>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Subject: Re: Why are we PageInit'ing buffers in RelationAddExtraBlocks()?
Date: 2018-12-20 00:39:33
Message-ID: 13071.1545266373@sss.pgh.pa.us
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Wed, Dec 19, 2018 at 5:37 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
>> What's gained by the logic of emitting that warning in VACUUM after a
>> crash? I don't really see any robustness advantages in it.

> I don't know. I am just normally reluctant to change things
> precipitously that are of long tenure.

Me too, but I think Andres has a point here. Those warnings in VACUUM
are ancient, probably predating the introduction of WAL :-(. At the
time there was good reason to be suspicious of zeroed pages in tables.
Now, though, we have (what we think is) a bulletproof crash recovery
procedure in which possibly-zeroed pages are to be expected; so we're
just causing users unnecessary alarm by warning about them. I think
it's reasonable to, if not remove the messages entirely, at least
downgrade them to a low DEBUG level.

regards, tom lane

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