Dear Richard,
you are right. So Postgres takes a lot of time to get out an
impossible result!
The query I wrote is just a test, the concatenation is only a dummy.
On 19/set/08, at 12:33, Richard Huxton wrote:
Andrea Moretto wrote:
I've got a table called DETAILS, the primary key is : DE_ID char(12),
there is another field CO_ID char (12).
If I run "explain analyze select * from details where co_id ||
co_id =
'0100760153722324445';" it runs a sequential scan not using the index
(which takes about 1000000 times than using the index):
That query can never return any rows. You're appending co_id to itself
then testing against a non-repeating string. Furthermore it's 19 chars
long rather than 24. Is this really what you're trying to do?
Read up on "indexes on expressions" in chapter 11 of the manuals, for
indexing this sort of thing. I don't think it will help you here
though.
--
Richard Huxton
Archonet Ltd
Andrea Moretto
moretto.andrea@xxxxxxxxx
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