|
PostgreSQL: Enhancements in 7.4: Performance: Better handling of joins
- Optimisation of explicit joins
- SELECT * FROM a JOIN (b JOIN c on(b.id=c.id)) ON (a.id=b.id)
- Evaluate join of b to c, then to a
- Generally decreases time required for planning, but some (closed) applications not correctly written
- Control with postgresql.conf: join_collapse_limit = 0
- Multicolumn hash joins
Page 17
|