Re: BUG #15321: XMLTABLE leaks memory like crazy

>>>>> "Andrew" == Andrew Gierth <andrew@tao11.riddles.org.uk> writes:

 >>> * I removed the "buildercxt" memory context. It seemed mostly
 >>> pointless, and I was disturbed by the MemoryContextResetOnly().
 >>> Per-value memory still uses the per-value memory context, but the
 >>> rest of the stuff is in the per-query context, which should be
 >>> pretty much the same.

 Andrew> A quick reading suggests that the per-value context should have
 Andrew> been changed to not be a child of "buildercxt" (which would
 Andrew> avoid the MemoryContextResetOnly issue - that's a good sign
 Andrew> that you've put a child context under the wrong parent). But
 Andrew> the use of the per-query context instead is exactly what causes
 Andrew> this blowup; compare with what nodeFunctionscan does with its
 Andrew> "argcontext" (and the corresponding comments in
 Andrew> ExecMakeTableFunctionResult).

And here's a patch (against pg10, but I don't think the code's changed
since) that I think does it the right way.

This works by changing the meaning of perValueCxt - it's now the
per-INPUT-value context (equivalent to FunctionScan's argcontext, but I
didn't change the name for simplicity), not per-output-value; for the
latter, we use the result exprcontext's per-tuple memory like everything
else does (cf. FunctionScan).

I've verified that this fixes the leak; it also passes all other tests I
have thrown at it. Anyone see any issues with this? (CC'ing in Pavel as
original author)

I'll apply it in due course unless anyone says otherwise.

--
Andrew (irc:RhodiumToad)