Uploaded image for project: 'IMPALA'
  1. IMPALA
  2. IMPALA-8759

Use double precision for HLL

    XMLWordPrintableJSON

    Details

    • Type: Improvement
    • Status: Open
    • Priority: Major
    • Resolution: Unresolved
    • Affects Version/s: Impala 3.2.0
    • Fix Version/s: None
    • Component/s: Backend
    • Labels:
    • Epic Color:
      ghx-label-3

      Description

      For /be/src/exprs/aggregate-functions-ir.cc the finalize function uses a float which is only capable of 6-9 digits of precision.  More accurate estimates for larger cardinalities (beyond 999,999) should be possible with double precision.  Another c++ implementation uses double as well https://github.com/dialtr/libcount

        Attachments

          Activity

            People

            • Assignee:
              Unassigned
              Reporter:
              peter.ebert Peter Ebert
            • Votes:
              0 Vote for this issue
              Watchers:
              2 Start watching this issue

              Dates

              • Created:
                Updated: