Re: BUG #15321: XMLTABLE leaks memory like crazy

>>>>> "PG" == PG Bug reporting form <noreply(at)postgresql(dot)org> writes:

PG> From a report on IRC:

PG> XMLTABLE runs a lot of setup code in the per-query memory context -
PG> resulting in allocations of copies of namespace names, other
PG> values, and _multiple copies of the passed-in XML document_, which
PG> are not freed anywhere.

Alvaro, I think this comment of yours from when you committed this work
is relevant:

>> I just pushed XMLTABLE, after some additional changes. Please test
>> it thoroughly and report any problems.
[...]
>> Some changes I made:
>> * 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.

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

--
Andrew (irc:RhodiumToad)