| From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Vadim Mikheev <vadim(at)krs(dot)ru> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgreSQL(dot)org |
| Subject: | Re: [HACKERS] Performance problem partially identified |
| Date: | 1999-05-29 05:24:15 |
| Message-ID: | 199905290524.BAA03240@candle.pha.pa.us |
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| Lists: | pgsql-hackers |
> > This could only be from the call to SetBufferCommitInfoNeedsSave in
> > the HeapTupleSatisfies macro. If I'm reading the code correctly,
> > that means that HeapTupleSatisfiesSnapshot() always changes the
> ^^^^^^^^^^^^^^
> > t_infomask field of the tuple.
>
> Not always but only if HEAP_XMIN_COMMITTED/HEAP_XMAX_COMMITTED
> are not setted. Run vacuum before update and SetBufferCommitInfoNeedSave
> will not be called. This func is just to avoid pg_log lookup
> without vacuum.
>
Yes, we store the transaction status on first in the tuple so we don't
have to look it up.
--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
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