Hi, We have recently performed an experimental evaluation of PostgreSQL's query optimizer. For example, we measured the contributions of cardinality estimation and the cost model on the overall query performance. You can download the resulting paper here: http://www.vldb.org/pvldb/vol9/p204-leis.pdf
Some findings: 1. Perhaps unsurprisingly, we found that cardinality estimation is the biggest problem in query optimization. 2. The quality of Postgres' cardinality estimates is not generally worse than that of the major commerical systems. 3. It seems to me that one obvious way to avoid many bad situations would be to disable nested loop joins when the inner relation is NOT an index scan. I hope this will be of interest to some of you. -- Viktor Leis -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
