Stamatis Zampetakis created HIVE-28252:
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Summary: AssertionError when using HiveTableScan with a HepPlanner
cluster
Key: HIVE-28252
URL: https://issues.apache.org/jira/browse/HIVE-28252
Project: Hive
Issue Type: Improvement
Components: CBO, Tests
Affects Versions: 4.0.0
Reporter: Stamatis Zampetakis
Assignee: Stamatis Zampetakis
The {{HiveTableScan}} operator throws an
[AssertionError|https://github.com/apache/hive/blob/7950967eae9640fcc0aa22f4b6c7906b34281eac/ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/reloperators/HiveTableScan.java#L153]
if the operator does not have the {{HiveRelNode.CONVENTION}} set.
The {{HepPlanner}} does not use any
[RelTraitDef|https://github.com/apache/calcite/blob/f854ef5ee480e0ff893b18d27ec67dc381ee2244/core/src/main/java/org/apache/calcite/plan/AbstractRelOptPlanner.java#L276]
so the default [empty traitset for the respective
cluster|https://github.com/apache/calcite/blob/f854ef5ee480e0ff893b18d27ec67dc381ee2244/core/src/main/java/org/apache/calcite/plan/RelOptCluster.java#L99]
is gonna be always empty.
In principle we should not be able to use the {{HiveTableScan}} operator with
{{HepPlanner}}. However, the optimizer heavily uses the {{HepPlanner}} (in fact
more than the {{VolcanoPlanner}} and it is reasonable to wonder how is this
possible given that this assertion is in place. The assertion is circumvented
by creating a cluster from a
[VolcanoPlanner|https://github.com/apache/hive/blob/7950967eae9640fcc0aa22f4b6c7906b34281eac/ql/src/java/org/apache/hadoop/hive/ql/parse/CalcitePlanner.java#L1620]
and then using it in the
[HepPlanner|https://github.com/apache/hive/blob/7950967eae9640fcc0aa22f4b6c7906b34281eac/ql/src/java/org/apache/hadoop/hive/ql/parse/CalcitePlanner.java#L2422].
This cluster usage is a bit contrived but does not necessarily need to change
at this stage.
Nevertheless, since the {{HiveTableScan}} operator is suitable to run with the
{{HepPlanner}} the assertion can be relaxed (or removed altogether) to better
reflect the actual usage of the operator, and allow passing a "true" HepPlanner
cluster inside the operator.
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