Re: slow update on 1M rows (worse with indexes)

On Thu, Feb 22, 2007 at 07:11:42PM +0100, Gabriel Biberian wrote:
> Create a new DB and load a dump of the above database with 976009 rows,
> then i perform updates on the whole table.  I recorded the time taken
> for each full update and the amount of extra disk space used.  Each
> consecutive update of the table is slower than the previous
> beebox@evobrik01:~$ time psql TOTO -c "UPDATE versions_9d SET flag=2"
> UPDATE 976009
> real    0m41.542s

You're creating a huge amount of dead rows by this kind of procedure. Try a
VACUUM in-between, or enable autovacuum. (Adjusting your WAL and
checkpointing settings might help too.)

Apart from that, do you really have a scenario that requires updating _all_
rows in your table regularly?

/* Steinar */
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