Re: [HACKERS] Some notes on optimizer cost estimates

> "Hiroshi Inoue" <Inoue@tpf.co.jp> writes:
> > I've wondered why we cound't analyze database without vacuum.
> > We couldn't run vacuum light-heartedly because it acquires an
> > exclusive lock for the target table. 
> 
> There is probably no real good reason, except backwards compatibility,
> why the ANALYZE function (obtaining pg_statistic data) is part of
> VACUUM at all --- it could just as easily be a separate command that
> would only use read access on the database.  Bruce is thinking about
> restructuring VACUUM, so maybe now is a good time to think about
> splitting out the ANALYZE code too.

I put it in vacuum because at the time I didn't know how to do such
things and vacuum already scanned the table.  I just linked on the the
scan.  Seemed like a good idea at the time.

It is nice that ANALYZE is done during vacuum.  I can't imagine why you
would want to do an analyze without adding a vacuum to it.  I guess
that's why I made them the same command.

If I made them separate commands, both would have to scan the table,
though the analyze could do it without the exclusive lock, which would
be good.

--  Bruce Momjian                        |  http://www.op.net/~candle pgman@candle.pha.pa.us               |  (610)
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