Re: Excessive memory usage in multi-statement queries w/ partitioning

Amit Langote <amitlangote09(at)gmail(dot)com> writes:
> Attached updated patch. Thanks again.

Pushed with a bit of further cleanup --- most notably, the way
you had execute_sql_string(), it was still leaking any cruft
ProcessUtility might generate. We can fix that by running
ProcessUtility in the per-statement context too.

I also dropped the optimization for a single/last statement in
execute_sql_string(), and simplified it to just always create
and delete a child context. This was based on a couple of
thoughts. The norm in this code path is that there's multiple
statements, probably lots of them, so that the percentage savings
from getting rid of one context creation is likely negligible.
Also, unlike exec_simple_query, we *don't* know that the outer
context is due to be cleared right afterwards. Since
execute_sql_string() can run multiple times in one extension
command, in principle we could get bloat from not cleaning up
after the last command of each string. Admittedly, it's not
likely that you'd have so many strings involved that that
amounts to a lot, but between following upgrade-script chains
and cascaded module loads, there could be more than a couple.
So it seems like the argument for saving a context creation is
much weaker here than in exec_simple_query.

I tried to improve the comments too. I noticed that the bit about
"(again, these must outlive the execution context)" seemed to be
a dangling reference --- whatever previous comment it was referring
to is not to be found anymore. So I made that self-contained.

regards, tom lane