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Re: ReadBuffer() error checking

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Neil Conway <neilc(at)samurai(dot)com>
Cc: PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: ReadBuffer() error checking
Date: 2004-11-13 23:37:08
Message-ID: 3774.1100389028@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-patches
Neil Conway <neilc(at)samurai(dot)com> writes:
> AFAIK, ReadBuffer() will elog on error, so callers can assume that the 
> buffer it returns is valid. The vast majority of ReadBuffer() call sites 
> make this assumption, but some went to the trouble of checking that the 
> returned buffer was valid and elog'ing if it was not. I've removed the 
> error checking from the latter since it is dead code.

Agreed.  I get the impression that at one time it was not so, but
certainly for the last many years there's been no need to test.

> I thought about adding an assertion (or even a precautionary 
> elog(ERROR)) to ReadBuffer to verify that the returned buffer is indeed 
> valid, but I didn't end up doing it. Feel free to raise your hand if you 
> think this is a good idea.

Nah; considering that the return statements invoke
BufferDescriptorGetBuffer, you'll probably get a core dump anyway
if there's something wrong ;-)

A related issue in the same general area is that the smgr code is
currently implemented to elog on error, but its API still reflects
an assumption that it will return a failure indication.  Changing
the API is a larger change than I want to see during late beta,
but it's a cleanup that would be reasonable to undertake during
a future development cycle, if you're interested.

			regards, tom lane

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Subject: Re: Give the TODO list a little more verbose explanation
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