16 квітня 2010 р. 17:19 Tom Lane <tgl@xxxxxxxxxxxxx> написав:
-- =?KOI8-U?B?96bUwcymyiD0yc3eydvJzg==?= <tivv00@xxxxxxxxx> writes:As was pointed out, even if we had such logic it wouldn't apply in this
> I've thought and someone in this list've told me that this should be done
> automatically.
example, because the equality conditions aren't real equalities but
OUTER JOIN conditions.
In this case you can copy condition to "ON" condition, not to where cause and this would work correct, e.g. "select something from a join b on a.x=b.y where a.x > n" <=> "select something from a join b on a.x=b.y and b.y > n where a.x > n".
As of making planner more clever, may be it is possible to introduce division on "fast queries" and "long queries", so that if after fast planning cost is greater then some configurable threshold, advanced planning techniques (or settings) are used. As far as I have seen in this list, many techniques are not used simply because they are too complex and could make planning take too much time for really fast queries, but they are vital for long ones.
Also same (or similar) threshold could be used to enable replanning for each run of prepared query - also an often complaint is that planned query is not that fast as is could be.
Best regards,
Vitalii Tymchyshyn
