Re: Per-tuple memory leak in 9.0

Dean Rasheed <dean.a.rasheed@gmail.com> writes:
> The problem is that the trigger code assumes that anything it
> allocates in the per-tuple memory context will be freed per-tuple
> processed, which used to be the case because the loop in ExecutePlan()
> calls ResetPerTupleExprContext() once each time round the loop, and
> that used to correspond to once per tuple.

> However, with the refactoring of that code out to nodeModifyTable.c,
> this is no longer the case because the ModifyTable node processes all
> the tuples from the subquery before returning, so I guess that the
> loop in ExecModifyTable() needs to call ResetPerTupleExprContext()
> each time round.

Hmmm ... it seems a bit unclean to be resetting the output-tuple
exprcontext at a level below the top of the plan.  I agree that that's
probably the sanest fix at the moment, but I fear we may need to revisit
this in connection with writable CTEs.  We might need a separate output
tuple context for each ModifyTable node, or something like that.
        regards, tom lane