Re: Parallel Seq Scan

On Sun, Oct 11, 2015 at 7:56 PM, Noah Misch <noah(at)leadboat(dot)com> wrote:
> I see no mention in this thread of varatt_indirect, but I anticipated
> datumSerialize() reacting to it the same way datumCopy() reacts. If
> datumSerialize() can get away without doing so, why is that?

Good point. I don't think it can. Attached is a patch to fix that.
This patch also includes some somewhat-related changes to
plpgsql_param_fetch() upon which I would appreciate any input you can
provide.

plpgsql_param_fetch() assumes that it can detect whether it's being
called from copyParamList() by checking whether params !=
estate->paramLI. I don't know why this works, but I do know that this
test fails to detect the case where it's being called from
SerializeParamList(), which causes failures in exec_eval_datum() as
predicted. Calls from SerializeParamList() need the same treatment as
calls from copyParamList() because it, too, will try to evaluate every
parameter in the list. Here, I've taken the approach of making that
check unconditional, which seems to work, but I'm not sure if some
other approach would be better, such as adding an additional Boolean
(or enum context?) argument to ParamFetchHook. I *think* that
skipping this check is merely a performance optimization rather than
anything that affects correctness, and bms_is_member() is pretty
cheap, so perhaps the way I've done it is OK.

--
Robert Haas
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