[CALCITE-4166] UnsupportedOperationException when getting distribution in metadata quey

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.21.0, 1.24.0
• Component/s: core
• Assignee: Unassigned
• Reporter: Krisztian Kasa
• Created: 07/Aug/20 08:04
• Updated: 17/Mar/23 02:26

Description

The RelDistribution is calculated by:
1. Get the Project input's RelDistribution. If it is a TableScan which scans a partitioned table the returned RelDistribution object contains the indexes of partition columns like:  RelDistribution(hash[0, 4])
2. If the project contains these columns we need a mapping to map the key indexes in the RelDistribution.

Mapping is generated here:
https://github.com/apache/calcite/blob/b3b3e06eef7eeedf2de32b44d061af7867633be6/core/src/main/java/org/apache/calcite/rel/metadata/RelMdDistribution.java#L164

This mapping is an INVERSE_FUNCTION
https://github.com/apache/calcite/blob/2088488ac8327b19512a76a122cae2961fc551c3/core/src/main/java/org/apache/calcite/rel/core/Project.java#L375
which does not support getTargetOpt

Stack trace from UT ( RelMdDistributionTest.java ) I created to reproduce the issue in Calcite:

[0;31;1mFAILURE   2.1sec, org.apache.calcite.rel.metadata.RelMdDistributionTest > test()
    java.lang.UnsupportedOperationException
        at org.apache.calcite.util.mapping.Mappings$AbstractMapping.getSourceOpt(Mappings.java:913)
        at org.apache.calcite.util.mapping.Mappings$InverseMapping.getTargetOpt(Mappings.java:1800)
        at org.apache.calcite.rel.RelDistributions$RelDistributionImpl.apply(RelDistributions.java:145)
        at org.apache.calcite.rel.metadata.RelMdDistribution.project(RelMdDistribution.java:166)
        at org.apache.calcite.rel.metadata.RelMdDistribution.distribution(RelMdDistribution.java:98)
        at org.apache.calcite.rel.metadata.RelMdDistributionTest.test(RelMdDistributionTest.java:76)

And a stacktrace from Hive where we hit this issue: cbo_query74_stacktrace.txt