Re: Composite Datums containing toasted fields are a bad idea(?)

Noah Misch <noah(at)leadboat(dot)com> writes:
> I wonder how it would work out to instead delay this new detoast effort until
> toast_insert_or_update().

That would require toast_insert_or_update() to know about every container
datatype. I doubt it could lead to an extensible or maintainable
solution.

I'm actually planning to set this patch on the shelf for a bit and go
investigate the other alternative, ie, not generating composite Datums
containing toast pointers in the first place. We now know that the idea
that we aren't going to take performance hits *somewhere* is an illusion,
and I still suspect that the other way is going to lead to a smaller and
cleaner patch. The main performance downside for plpgsql might be
addressable by making sure that plpgsql record variables fall on the "heap
tuple" rather than the "composite Datum" side of the line. I'm also quite
concerned about correctness: I don't have a lot of confidence that this
patch has closed every loophole with respect to arrays, and it hasn't even
touched ranges or any of the related one-off bugs that I believe exist.

regards, tom lane