Henrik wrote: > Correct. I changed the statistics to 500 in tbl_file.file_name and now the > statistics is better. But now my big seq scan on tbl_file_Structure back > and I don't know why. Hmm, I think the problem here is that it needs to fetch ~200000 tuples from tbl_file_structure one way or the other. When it misestimated the tuples from tbl_file it thought it would only need to do the indexscan in tbl_file_structure a few times, but now it realizes that it needs to do it several thousands of times and it considers the seqscan to be cheaper. Perhaps you would benefit from a higher effective_cache_size or a lower random_page_cost (or both). I think this is a problem in the optimizer: it doesn't correctly take into account the fact that the upper pages of the index are most likely to be cached. This has been discussed a lot of times but it's not a simple problem to fix. -- Alvaro Herrera http://www.amazon.com/gp/registry/CTMLCN8V17R4 Este mail se entrega garantizadamente 100% libre de sarcasmo. ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
