somandal opened a new pull request, #9078:
URL: https://github.com/apache/pinot/pull/9078
Today MV columns as the first expression in a Selection Order By query fails
during query execution. The error seen today is:
```
18:25:22.961 BaseCombineOperator - Caught exception while processing query:
QueryContext{_tableName='testTable', _subquery=null,
_selectExpressions=[mvFloatCol], _aliasList=[null], _filter=mvFloatCol < '5',
_groupByExpressions=null, _havingFilter=null, _orderByExpressions=[mvFloatCol
ASC], _limit=10, _offset=0, _queryOptions={}, _expressionOverrideHints={},
_explain=false}
java.lang.ClassCastException: class [F cannot be cast to class
java.lang.Comparable ([F and java.lang.Comparable are in module java.base of
loader 'bootstrap')
at
org.apache.pinot.core.operator.combine.MinMaxValueBasedSelectionOrderByCombineOperator.processSegments(MinMaxValueBasedSelectionOrderByCombineOperator.java:210)
~[classes/:?]
at
org.apache.pinot.core.operator.combine.BaseCombineOperator$1.runJob(BaseCombineOperator.java:101)
~[classes/:?]
at
org.apache.pinot.core.util.trace.TraceRunnable.run(TraceRunnable.java:40)
~[classes/:?]
at
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) ~[?:?]
at java.util.concurrent.FutureTask.run(FutureTask.java:264) ~[?:?]
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
~[?:?]
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
~[?:?]
at java.lang.Thread.run(Thread.java:834) [?:?]
```
This PR throws an `UnsupportedOperationException` during the server side
planning phase when it identifies a MV column as the first expression in the
selection order-by query to provide users with a better message about why the
query fails.
Note that this PR only errors out the scenario when the MV column is the
first expression in the order-by expression list rather than erroring out
whenever any MV column is present in the order-by expression list. The reason
for this is to maintain backward incompatibility. Today if a mix of SV and MV
columns are present in a selection order-by query, and if the first expression
is a SV column then the query execution completes successfully. The query
execution failure only occurs when the MV column is the first expression.
Selection order-by on MV columns don't make sense semantically which is why
it is better to error out in a meaningful way as the error thrown on the query
execution failure requires debugging to understand why it failed.
cc @siddharthteotia
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