On 16/03/10 13:05, Arnaud Lesauvage wrote:
Hi all !
PostgreSQL 8.4 here.
I have a simple update query that looks like this :
UPDATE t1
SET col = t2.col
FROM t2
WHERE t1.key1 = t2.key1 AND t1.key2 = t2.key2;
There is an index on (key1,key2) on the joined table (t2).
This query does not use the index.
What does it do, then? The output of EXPLAIN would be a start if EXPLAIN
ANALYSE is too expensive.
Oh - and how many rows will this actually update?
--
Richard Huxton
Archonet Ltd
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