Github user zuyu commented on a diff in the pull request:
https://github.com/apache/incubator-quickstep/pull/45#discussion_r68846898
--- Diff: query_optimizer/ExecutionGenerator.cpp ---
@@ -1575,21 +1579,12 @@ void ExecutionGenerator::convertSort(const
P::SortPtr &physical_sort) {
merged_runs_destination_proto->set_relational_op_index(merge_run_operator_index);
sorted_output_destination_proto->set_relational_op_index(merge_run_operator_index);
- // Do not add merged_runs_relation into 'temporary_relation_info_vec_'
- // and create the DropTableOperator for it at the end. Instead, add the
drop
- // operator right here, because the relation won't be used by any other
operator.
- const QueryPlan::DAGNodeIndex drop_merged_runs_index =
- execution_plan_->addRelationalOperator(
- new DropTableOperator(
- query_handle_->query_id(),
- *merged_runs_relation,
- optimizer_context_->catalog_database(),
- false /* only_drop_blocks */));
- execution_plan_->addDirectDependency(
- drop_merged_runs_index,
- merge_run_operator_index,
- true /* is_pipeline_breaker */);
-
+ // REVIEW(Shixuan): There might be an issue with the original code: if a
throw
+ // happens before the plan is executed, merged_runs_relation will not be
dropped
+ // by dropAllTemporaryRelations() if not added to
temporary_relation_info_vec,
+ // which might cause "RelationNameCollision".
+ temporary_relation_info_vec_.emplace_back(merge_run_operator_index,
--- End diff --
I think the actual executing order of `DropTable` depends on the scheduler
based on a topological order. But in the optimizer generated DAG, a `sort`
operator typically is placed as the last one, so in most case the new way is
similar to the old way.
I suggest to debug the query w/ `window aggregation` by printing out the
DAG and the operator finish order (hack in `query_execution/QueryManager`).
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