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Re: advancing snapshot's xmin

From: Gregory Stark <stark(at)enterprisedb(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>, "Neil Conway" <neilc(at)samurai(dot)com>, "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, "Pg Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: advancing snapshot's xmin
Date: 2008-03-26 15:05:50
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

>> Consider a data loading job which has millions of INSERT statements in a file.
>> Currently if you put them all in a transaction it takes a single snapshot and
>> runs them all with the same snapshot.
>> If you reset xmin whenever you have no live snapshots then that job would be
>> doing that between every INSERT statement.
> These statements are 100% nonsense.

Uhm, yeah, I somehow didn't write was I was thinking. I didn't mean to say we
would be taking a new snapshot for each INSERT but that we would be resetting
xmin for each INSERT. Whereas currently we only set xmin once when we set the
serializable snapshot.

  Gregory Stark
  Ask me about EnterpriseDB's On-Demand Production Tuning

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