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
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