Merlin Moncure <> writes:
> Hm, maybe, instead of trying to figure out if in a loop, set a
> 'called' flag  with each statement and only cache when touched the
> second time.  (If that's easier, dunno).

Well, then you just guarantee to lose once.  I think Jan's sketch of
marking potentially-cacheable expressions at compile time sounds
promising.  I'm envisioning a counter that starts at 1 normally or 0 in a
DO block, increment at beginning of parsing a loop construct, decrement at
end; then mark expressions/statements as cacheable if counter>0.

Of course the next question is what exactly to do differently for a
noncacheable expression.  My recollection is that that's all tied
pretty tightly to the plancache these days, so it might take a little

                        regards, tom lane

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