Re: On query rewrite

>>>>> "Alvaro" == Alvaro Herrera <alvherre@dcc.uchile.cl> writes:
   >> For instance, in the presence of a view or a subquery, does PG   >> do a subquery to join transformation ?
   Alvaro> Yes, there are transformations of this sort, but they are   Alvaro> not called query rewrite in the code's
terminology,but   Alvaro> "optimization" -- rewrite (rules and views) happens to the   Alvaro> parsed statement, and
theoptimizer works on the output of   Alvaro> rewriting.  So actually the optimizations happen whether   Alvaro> there
wereor not rules or views.
 

Interesting .. so these are rule-based then ? Not cost-based ?

I understand that there is a cost-based optimizer anyway that does the
planning and selects the right plan .. but does this come _after_ all
these transformations ? Or does it happen along with the
transformations ? 
   Alvaro> The query's path is SQL -> parse -> rewrite -> optimize ->   Alvaro> execute

Can you please point me to the code that indeed does such
transformations ? 

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Sailesh
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