Trafodion

  1. Bug #1392555
  2. Comment #2

Comment 2 for bug 1392555

Revision history for this message
Trafodion-Gerrit (neo-devtools) wrote : Fix merged to core (master)

Reviewed: https://review.trafodion.org/717
Committed: https://github.com/trafodion/core/commit/582b09c7bc8325af01b35b8b2b52ae6d7a9d0d77
Submitter: Trafodion Jenkins
Branch: master

commit 582b09c7bc8325af01b35b8b2b52ae6d7a9d0d77
Author: Barry Fritchman <email address hidden>
Date: Thu Nov 20 22:42:14 2014 +0000

    Change default for USTAT_USE_IS_WHEN_NO_STATS

    This cqd was originally set to OFF by default, causing
    internal sort not to be used in cases where there are
    no existing histograms. Internal sort is known to
    underperform when there are a small number of unique
    values for a column, and without prior histograms, the
    unique entry count is unknown.

    However, experience with POCs has shown that using internal
    sort in these situations (unique count unknown) is in
    general significantly faster than not using it, so the
    default setting has been changed to ON.

    Running developer regressions with this setting exposed a
    bug that occurs when internal sort is used on an empty table
    that previously did contain rows. This change includes a known
    diffs file for the failing test until the bug (LP 1393930)
    can be fixed.

    Change-Id: I9ff6672a168016fb83fadb26b40a30c7fa3eee6c
    Closes-Bug: #1392555