Re: INNER JOIN ON vs ','+WHERE

"Thalis A. Kalfigopoulos" <thalis@cs.pitt.edu> writes:
> Changing the type of "join" syntax affects the plan-generation time
> and the execution-time. Would it be logical to EXPLAIN the query once
> using the 'FROM a,b,c WHERE...' syntax and then assuming that it
> returns the optimal execution plan, use the join order of this plan to
> rewrite the query in a 'a INNER JOIN b ON ... INNER JOIN c ON...'
> fashion so as to save the plan generation time from then on?

Yup, that's more or less what the documentation is trying to suggest,
down at the bottom.

> Is the plan generation time significant compared to actual execution
> time when we are talking about large tables even if there's lots of
> them? The question actually is: is there any more time involved to
> plan generation other than what it takes when I do an EXPLAIN on the
> query? After that, all time is consumed to performing the actual
> joins, correct?

EXPLAIN runs the same planner as actual execution does.  If EXPLAIN
doesn't take long enough to bother you, then you don't need to worry
about planning time.

            regards, tom lane