Re: Allowing join removals for more join types

On 2014-06-04 20:04:07 -0400, Noah Misch wrote:
> On Wed, Jun 04, 2014 at 10:14:42AM -0400, Tom Lane wrote:
> > It's possible that we could apply the optimization only to queries that
> > have been issued directly by a client, but that seems rather ugly and
> > surprise-filled.
>
> ... such as this idea. It's a good start to a fairly-hard problem. FKs are
> also always valid when afterTriggers->query_depth == -1, such as when all
> ongoing queries qualified for EXEC_FLAG_SKIP_TRIGGERS. What else? We could
> teach trigger.c to efficiently report whether a given table has a queued RI
> trigger. Having done that, when plancache.c is building a custom plan, the
> planner could ignore FKs with pending RI checks and use the rest. At that
> point, the surprises will be reasonably-isolated.

A bit more crazy, but how about trying trying to plan joins with a added
one-time qual that checks the size of the deferred trigger queue? Then
we wouldn't even need special case plans.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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