On Sun, Oct 31, 2010 at 6:35 PM, Peter Neal <doabackflip@xxxxxxxxx> wrote: > Is there any way I can explain this to postgres? When I query the parent > table of the partitions, "SELECT * from A, B where a.id=b.id;", the planner > does a sequential scan on A, A1, A2, ... an index scan on B, B1, B2, ... > then a nested loop, which generally takes a while. > The index scan on the B tables should be very quick to discount the tables which have no matching data. It will take I expect exactly one page of the index to determine that. Assuming you have plenty of RAM, those pages should remain in your memory and not cause any disk I/O after the first such iteration. > As I say, I presume this is because the planner does not know that there is > no overlap in 'id' values between the different partitions - is there any > way to express this? I don't believe there is. If the inside loop is using an index scan on each partition, that's about as good as you can do. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
