Re: Why Does UPDATE Take So Long?

Bill Thoen <bthoen(at)gisnet(dot)com> schrieb:

> Working with PG 8.1 I'm trying to update a char(4) column, and it's
> taking a very long time; 15 minutes so far and no end in sight. From the
> explain, it doesn't seem like it should take that long, and this column
> is not indexed. Sure, there's 2.7 million records but it only takes a
> few minutes to scan the whole file. Is there some special overhead I
> should be aware of with an UPDATE? I VACUUMed and ANALYZEd first, too.
>
> Or am I just expecting too much?
>
> Here's the explain:
> explain UPDATE farms SET prog_year='2007';
> QUERY PLAN
> ----------------------------------------------------------------
> Seq Scan on farms (cost=0.00..59144.07 rows=2772207 width=54)
> (1 row)

Please provide us an EXPLAIN ANALYSE. But without a WHERE-condition a
seq-scan are logical, and PG has to rewrite the whole table and the
transaction-log.

Andreas
--
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