Richard Huxton wrote:
Sebastian Böck wrote:
Richard Huxton wrote:
Can you post the output from your "explain analyse" calls too? The
statistics aren't going to be the same on different machines.
Sure, here it is.
Thanks. (PS - remember to cc the list too).
[output of EXPLAIN ANALYZE]
OK - so what you want to know is why index "test_999" is used in the
second but not the first, even though both return the same rows.
The fact is that the conditional index:
CREATE INDEX test_999 ON test (datum)
WHERE version = '999' OR approved IS NOT NULL;
AFAIK looks at the WHERE clause of your query to determine where it can
run. Don't forget that the planner needs to pick which index is best
*before* it starts fetching data.
So - in the first example there might be rows where e.g. t.version=998
which means test_999 would be a poor choice of index.
But what if the table users contains only 1 row and the column "version"
has a value of "999"?
Are there any other options to speed up this kind of query?
Thanks so far
Sebastian
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