[jira] [Created] (FLINK-1214) Prevent partitioning pushdown unless partitions fields match exactly

["Stephan Ewen (JIRA)" <ji...@apache.org>]

Stephan Ewen created FLINK-1214:
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             Summary: Prevent partitioning pushdown unless partitions fields match exactly
                 Key: FLINK-1214
                 URL: https://issues.apache.org/jira/browse/FLINK-1214
             Project: Flink
          Issue Type: Bug
          Components: Optimizer
    Affects Versions: 0.8-incubating
            Reporter: Stephan Ewen
            Assignee: Stephan Ewen
             Fix For: 0.8-incubating


Consider an operation grouped on fields (A, B), followed by an operation grouped on field (A).

Right now, the optimizer can push down the partitioning on (A), which serves both operations (the first step locally still groups by A and B). This may however by a bad idea for the cases where the field A has a low cardinality, or the value distribution is skewed.

Since we cannot determine that robustly yet, I suggest to disable this optimization for now.



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