On Sun, Apr 8, 2018 at 1:04 PM, Jeevan Chalke <jeevan.chalke@enterprisedb.com> wrote: > Hi, > > At some places, I have observed that we are adding a partial path even when > rel's consider_parallel is false. Due to this, the partial path added has > parallel_safe set to false and then later in create_gather_path() assertion > fails. >
+ /* If parallelism is not possible, return. */ + if (!rel->consider_parallel || !bms_is_empty(required_outer)) + return;
In this case shouldn't we set the rel's consider_parallel flag correctly rather than avoiding adding the path to it as we do in recurse_set_operations?
In recurse_set_operations() we are building a new rel and setting its properties from the final_rel. consider_parallel there is just copied from the final_rel. However, in set_subquery_pathlist(), rel is the input parameter here and we are trying to add a partial path to it without looking at its consider_parallel field. This patch does that.
And if we want to set consider_parallel for the rel, then it should have been done prior to this function itself. And I am not sure where that exactly but not in this function I guess.
2. @@ -331,7 +331,7 @@ recurse_set_operations(Node *setOp, PlannerInfo *root, * to build a partial path for this relation. But there's no point in * considering any path but the cheapest. */ - if (final_rel->partial_pathlist != NIL) + if (final_rel->consider_parallel && final_rel->partial_pathlist != NIL)
What problem did you see here or is it just for additional safety? Ideally, if the consider_parallel is false for a rel, it's partial path list should also be NULL.
I actually wanted to have rel->consider_parallel in the condition (yes, for additional safety) as we are adding a partial path into rel. But then observed that it is same as that of final_rel->consider_parallel and thus used it along with other condition.
I have observed at many places that we do check consider_parallel flag before adding a partial path to it. Thus for consistency added here too, but yes, it just adds an additional safety here.
