Re: Name for new VACUUM

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: mlw <markw(at)mohawksoft(dot)com>
Cc: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Name for new VACUUM
Date: 2001-08-03 14:25:57
Message-ID: 20228.996848757@sss.pgh.pa.us
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mlw <markw(at)mohawksoft(dot)com> writes:
> ... people looked at me like I had two heads when I told them about
> "vacuum." It wasn't obvious to them what it did.

I won't dispute that, but changing a command name that's been around for
ten or fifteen years strikes me as a recipe for more confusion, not
less.

> However, saying that VACUUM NOLOCK and VACUUM LOCK do "more-or-less
> the same thing" really isn't so. Think about it, the VACUUM LOCK,
> practically rebuilds a tables representation,

It does no such thing. The only difference is that it's willing to move
a few tuples around if it can thereby free up (and truncate) whole pages
at the end of the table. (In a live system you'd better hope it's only
a few tuples, anyway ;-) ... or you'll be waiting a long time.) It
doesn't even do a complete defrag; it stops moving tuples as soon as it
finds that it won't be able to truncate the table any further. So
there's *not* that much difference.

> VACUUM DEFRAG?
> VACUUM COMPRESS?

While these look kinda ugly to me, I can find no stronger objection than
that. (Well, maybe I could complain that these overstate what old-style
vacuum actually does, but that's even weaker.) What do other people
think?

regards, tom lane

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