| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com> |
| Cc: | "Bill Thoen" <bthoen(at)gisnet(dot)com>, pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Need Some Explanation of an EXPLAIN |
| Date: | 2008-09-26 21:25:00 |
| Message-ID: | 27774.1222464300@sss.pgh.pa.us |
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| Lists: | pgsql-general |
"Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com> writes:
> On Fri, Sep 26, 2008 at 12:13 PM, Bill Thoen <bthoen(at)gisnet(dot)com> wrote:
>> 2.) How can I make this update faster?
> Get a faster server?
Increasing work_mem might help. If the hashtable size estimate is
right, you'd need something like 100MB to be sure that the join gets
done in only one batch.
Also, if a lot of the rows needn't actually change, it'd be worthwhile
to add a WHERE clause:
UPDATE growers
SET grower_id = id2.grower_id
FROM id2 WHERE growers.fsa_id = id2.fsa_id
AND growers.grower_id != id2.grower_id
regards, tom lane
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