On Wed, Feb 28, 2024 at 8:11 PM Dean Rasheed <dean.a.rash...@gmail.com> wrote: > > On Wed, 28 Feb 2024 at 09:16, jian he <jian.universal...@gmail.com> wrote: > > > > + oldcontext = MemoryContextSwitchTo(estate->es_query_cxt); > > + > > + node->as_epq_tupdesc = lookup_rowtype_tupdesc_copy(tupType, tupTypmod); > > + > > + ExecAssignExprContext(estate, &node->ps); > > + > > + node->ps.ps_ProjInfo = > > + ExecBuildProjectionInfo(castNode(Append, node->ps.plan)->epq_targetlist, > > + > > EvalPlanQualStart, EvalPlanQualNext will switch the memory context to > > es_query_cxt. > > so the memory context switch here is not necessary? > > > > Yes it is necessary. The EvalPlanQual mechanism switches to the > epqstate->recheckestate->es_query_cxt memory context, which is not the > same as the main query's estate->es_query_cxt (they're different > executor states). Most stuff allocated under EvalPlanQual() is > intended to be short-lived (just for the duration of that specific EPQ > check), whereas this stuff (the TupleDesc and Projection) is intended > to last for the duration of the main query, so that it can be reused > in later EPQ checks. > sorry for the noise. I understand it now.
Another small question: for the Append case, we can set/initialize it at create_append_plan, all other elements are initialized there, why we set it at set_append_references. just wondering.
