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  1. Calcite
  2. CALCITE-732

Implement multiple distinct-COUNT using GROUPING SETS

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Details

    • Bug
    • Status: Closed
    • Major
    • Resolution: Fixed
    • None
    • 1.4.0-incubating
    • None
    • None

    Description

      Currently if a query has COUNT(DISTINCT x) and COUNT(DISTINCT y) we compute the distinct counts separately and combine them using a join. The join isn't too expensive (because usually the GROUP BY has only a few keys) but we make multiple scans over the base table.

      I think we could translate multiple distinct-counts into a GROUPING SETS query (i.e. an Aggregate with more than one element in the groupSets field). If the underlying engine can evaluate that efficiently, then we have saved ourselves a join and several scans.

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          relates to

          Bug - A problem which impairs or prevents the functions of the product. CALCITE-6332 Optimization CoreRules.AGGREGATE_EXPAND_DISTINCT_AGGREGATES_TO_JOIN produces incorrect results for aggregates with groupSets

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Closed

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              julianhyde Julian Hyde
              julianhyde Julian Hyde
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              Dates

                Created:
                Updated:
                Resolved: