On Mon, Apr 17, 2023 at 10:57 AM Richard Guo <guofengli...@gmail.com> wrote:
> The initPlan has been moved from the Result node to the Gather node. As > a result, when doing tuple projection for the Result node, we'd get a > ParamExecData entry with NULL execPlan. So the initPlan does not get > chance to be executed. And we'd get the output as the default value > from the ParamExecData entry, which is zero as shown. > > So now I begin to wonder if this wrong result issue is possible to exist > in other places where we move initPlans. But I haven't tried hard to > verify that. > I looked further into this issue and I believe other places are good. The problem with this query is that the es/ecxt_param_exec_vals used to store info about the initplan is not the same one as in the Result node's expression context for projection, because we've forked a new process for the parallel worker and then created and initialized a new EState node, and allocated a new es_param_exec_vals array for the new EState. When doing projection for the Result node, the current code just goes ahead and accesses the new es_param_exec_vals, thus fails to retrieve the info about the initplan. Hmm, I doubt this is sensible. So now it seems that the breakage of regression tests is more severe than being cosmetic. I wonder if we need to update the comments to indicate the potential wrong results issue if we move the initPlans to the Gather node. Thanks Richard
