On Sat, Oct 17, 2015 at 12:06 PM, Noah Misch <n...@leadboat.com> wrote: > > On Sat, Oct 17, 2015 at 11:00:57AM +0530, Amit Kapila wrote: > > On Sat, Oct 17, 2015 at 6:15 AM, Noah Misch <n...@leadboat.com> wrote: > > > On Thu, Oct 15, 2015 at 04:30:01PM +0530, Amit Kapila wrote: > > > > On Mon, Oct 12, 2015 at 9:16 PM, Robert Haas <robertmh...@gmail.com> wrote: > > > > > 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. > > > > > > > > From what I understood by looking at code in this area, I think the > > check > > > > params != estate->paramLI and code under it is required for parameters > > > > that are setup by setup_unshared_param_list(). Now unshared params > > > > are only created for Cursors and expressions that are passing a R/W > > > > object pointer; for cursors we explicitly prohibit the parallel > > > > plan generation > > > > and I am not sure if it makes sense to generate parallel plans for > > > > expressions > > > > involving R/W object pointer, if we don't generate parallel plan where > > > > expressions involve such parameters, then SerializeParamList() should > > not > > > > be affected by the check mentioned by you. > > > > > > The trouble comes from the opposite direction. A setup_unshared_param_list() > > > list is fine under today's code, but a shared param list needs more help. To > > > say it another way, parallel queries that use the shared estate->paramLI need, > > > among other help, the logic now guarded by "params != estate->paramLI". > > > > > > > Why would a parallel query need such a logic, that logic is needed mainly > > for cursor with params and we don't want a parallelize such cases? > > This is not about mixing cursors with parallelism. Cursors get special > treatment because each cursor copies its param list. Parallel query also > copies (more precisely, serializes) its param list. You need certain logic > for every param list subject to being copied. >
I am not denying from that fact, the point I wanted to convey here is that the logic guarded by "params != estate->paramLI" in plpgsql_param_fetch is only needed if cursors are in use otherwise we won't need them even for parallel query. With Regards, Amit Kapila. EnterpriseDB: http://www.enterprisedb.com
