>> No, tuplestore_putvalues is only responsible for the memory it >> allocates itself, which belongs to the tuplestore, it has nothing to >> do with the memory allocated by its caller - and XmlTableGetValue >> does quite a few allocations.
Pavel> Maybe I used wrong words. Sorry, my English lang is not good.
Pavel> In master tfuncLoadRows switch to tstate->perValueCxt. You Pavel> change it by switch econtext->ecxt_per_tuple_memory what is Pavel> wrong I thing.
Pavel> If we don't change memory context, we will stay inside Pavel> perValueCxt. And this context will be cleaned outside.
Yes, but it won't be cleaned up until _all_ the rows from a single call have been generated, which means that the allocations from GetValue have been (uselessly) accumulating during this time, wasting memory.
We do need a context that is reset for every output row, as perValueCxt used to be. I don't see why this is even in question. >> Before, you were using perValueCxt and resetting it once per GetValue >> call. Since my patch takes perValueCxt to use for another purpose >> instead, it needs to be replaced, and econtext->ecxt_per_tuple_memory >> is suitable for the job (and consistent with functionscan).
Pavel> I think so using cxt_per_tuple_memory is not necessary - and my Pavel> patch is working too.
Working, just using more memory than it needs to.
Pavel> Just I removed MemoryContextReset(tstate->perValueCxt) after Pavel> tuplestore_putvalues. It is possible, because Pavel> tstate->perValueCxt is cleaned immediately in caller Pavel> tfuncFetchRows function.
But that's not "immediately" because tfuncLoadRows is looping over the FetchRow call, and calling GetValue for each column in that row, and in your version it is _not cleaning up memory in that loop_.
ok, now I am maybe understand to your motivation.
Usually, loading row should be memory cheap operation, but sure some bytes it can take.
Then I don't like too much using ecxt_per_tuple_memory for this. Maybe better to create own short life context for purpose. Or do better comments about using this memory context for very short life task, please.
