Jinfeng Ni created DRILL-4541:
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Summary: Make sure query planner does not generate operators with
mixed convention trait
Key: DRILL-4541
URL: https://issues.apache.org/jira/browse/DRILL-4541
Project: Apache Drill
Issue Type: Bug
Components: Query Planning & Optimization
Reporter: Jinfeng Ni
Per the discussion [1] in the PR of DRILL-4531, we should fix the query planner
rules used in Drill planning, such that it will not generate Rels with mixed
convention trait. For instance, a LogicalFilter should only have child with
NONE convention; it should not have child with LOGICAL convention.
The mixed Rels will cause planner either hang (as reported in DRILL-4531 and
DRILL-3257), or do wasted work by firing rules against the mixed Rels.
I think the reason that we have such mixed rels is we have different kinds of
rules, used in a single Volcano planning phase.
1) Rule matchs base class Filter/Project, etc only.
2) Rule matches LogicalFilter/LogicalProject, etc
3) Rule matches DrillFilter/DrillProject, etc.
3) Rule uses copy() method to generate a new Rel
4) Rule uses RelFactory to generate a new Rel.
5) convent rule, which convert from Calcite logical (NONE/Enumerable) to Drill
logical (LOGICAL)
For instance, ProjectMergeRule, which matches base Project, yet uses default
RelFactory, will match both LogicalProject and DrillProject, but produce
LogicalProject as outcome. That will cause the mixed rels.
2 things we may consider to fix this:
1) Separate the convent rules from the other transformation rules. Apply
convert rule first, then all the transformation rules match DrillLogical only.
2) Every rule that Drill uses, except for convert rules, should assert the
convention of input and output have the same convention.
[1] https://github.com/apache/drill/pull/444
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