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  1. IMPALA
  2. IMPALA-8095

Detailed expression cardinality tests

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    Details

    • Type: Improvement
    • Status: Resolved
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: Impala 3.1.0
    • Fix Version/s: Impala 3.2.0
    • Component/s: Frontend
    • Labels:
      None
    • Epic Color:
      ghx-label-4

      Description

      Cardinality is a critical input to the query planning process, especially join planning. Impala has many high-level end-to-end tests that implicitly test cardinality at the "wholesale" level: A test will produce a wrong result if the cardinality is badly wrong.

      But, at present, no detailed unit tests exist for this topic. This ticket asks to add tests for:

      • Table cardinality, NDV values and null count in metadata retrieved from HMS.
      • Table cardinality, NDV values and null counts in metadata presented to the query.
      • Expression NDV and selectivity values (which derive from table cardinality and column NDV.)

      Since none of the existing "functional" tables provide the level of detail needed for these tests, add a new test table specifically for this task.

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            • Assignee:
              Paul.Rogers Paul Rogers
              Reporter:
              Paul.Rogers Paul Rogers
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              • Created:
                Updated:
                Resolved: