PostgreSQL选择语句非常慢，因为小的连接/其中的过滤器。

2013-05-29: Updated question with latest configuration and extra info. Earlier I was testing in a virtualbox image. Now I am testing on the productive server, which reflects the real world much better. Question should be fully clear now. If you have helped me before, read again carefully2013-05-29: Updated question with latest config