Re: Reducing overhead for repeat de-TOASTing

Simon Riggs <simon@2ndquadrant.com> writes:
> You've not covered the idea that we just alter the execution so we just
> detoast once.

That's because I already considered and rejected that idea.  There's
no very good place to do it.  See thread on postgis-devel:

http://postgis.refractions.net/pipermail/postgis-devel/2008-June/003091.html

Aside from the problems mentioned there, there's the issue that a lower
plan level doesn't have any way to know whether the value will be needed
at all.  We could look for references to the Var but it's entirely
possible that the Var is being passed to some function that doesn't
require a fully detoasted result.  It wouldn't do for this
"optimization" to disable the slice-fetch feature...
        regards, tom lane