On 31 October 2012 19:44, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Before 9.2, we didn't have this problem in this guise because we didn't
> generate parameterized paths bottom-up; instead, given that we had
> already decided to join t2 and t3 for some reason, we would look to see
> what indexpaths we could make for t1 using values from t2 and/or t3.
> However, that approach had big problems of its own: it couldn't find
> plans that involved pushing parameters down through an intervening join.
Given that most joins patterns are repeated consistently across
multiple SQL statements, is it possible to pre-calculate paths at
ANALYZE time, or perhaps cache them (persistently?) when first
generated? That way we just look up best paths, which would make join
planning much faster.
-- Simon Riggs http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training & Services