LIMIT clause extremely slow
Hi,
I have an issue using a limit clause, f.ex.
SELECT * FROM table WHERE (index1 > 1 OR (index1 = 1 AND index2 > 5)) ORDER
BY index1, index2 LIMIT 1
index1 and index2 are index fields of datatype integer.
This takes some 100 times longer than in Mysql or other databases under same
conditions (and I have to repeat this command very often, so time is adding
up).
I have read in some forums that you can fasten it up by saying
ORDER BY index1 + 0, index2 + 0
The result is better, but still very slow.
Using version 16.1
Thanks for your help and best regards, Florian Melzer
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On Nov 15, 2023, at 08:46, Melzer Kassensysteme <office@melzer-kassen.com> wrote:
SELECT * FROM table WHERE (index1 > 1 OR (index1 = 1 AND index2 > 5)) ORDER BY index1, index2 LIMIT 1
Can you show the output of the query running under EXPLAIN ANALYZE ... ?
On Wed, 2023-11-15 at 17:46 +0100, Melzer Kassensysteme wrote:
SELECT * FROM table WHERE (index1 > 1 OR (index1 = 1 AND index2 > 5)) ORDER BY index1, index2 LIMIT 1
index1 and index2 are index fields of datatype integer.
This takes some 100 times longer than in Mysql or other databases
This is not a bug; at worst, it is a performance problem.
For good performance, rewrite the query to
SELECT * FROM "table"
WHERE (index1, index2) > (1, 5)
ORDER BY index1, index2
LIMIT 1;
and make sure you have an index on (index1, index2).
Yours,
Laurenz Albe