Horton

Re: advancing snapshot's xmin

Gregory Stark <stark@enterprisedb.com>

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From: Gregory Stark <stark@enterprisedb.com>
To: "Tom Lane" <tgl@sss.pgh.pa.us>
Cc: "Heikki Linnakangas" <heikki@enterprisedb.com>, "Neil Conway" <neilc@samurai.com>, "Alvaro Herrera" <alvherre@commandprompt.com>, "Pg Hackers" <pgsql-hackers@postgresql.org>
Date: 2008-03-26T15:05:50Z
Lists: pgsql-hackers 
"Tom Lane" <tgl@sss.pgh.pa.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
  EnterpriseDB          http://www.enterprisedb.com
  Ask me about EnterpriseDB's On-Demand Production Tuning