[jira] [Created] (TRAFODION-2282) Optimizer histogram cache is sometimes never refreshed

["David Wayne Birdsall (JIRA)" <ji...@apache.org>]

David Wayne Birdsall created TRAFODION-2282:
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             Summary: Optimizer histogram cache is sometimes never refreshed
                 Key: TRAFODION-2282
                 URL: https://issues.apache.org/jira/browse/TRAFODION-2282
             Project: Apache Trafodion
          Issue Type: Bug
          Components: sql-cmp
    Affects Versions: 2.1-incubating
         Environment: All
            Reporter: David Wayne Birdsall
            Assignee: David Wayne Birdsall
             Fix For: 2.1-incubating


Here's the scenario:

In session 1, create a table T1 and populate it with, say, 200000 or more rows.

In session 2, prepare a query that selects from T1. For example, select A,COUNT(*) FROM T1 GROUP BY A. The query should compile fine, but you should see missing statistics warning messages (warning codes 6007 and 6008).

In session 1, do "update statistics for table t1 on every column"

In session 2, prepare other queries over a period of time. What should happen is that after about an hour, the Optimizer decides to refresh the histograms. However, due to a bug, it might never do so. So, the missing statistics warnings (6007, 6008) never go away. Worse, the prepares never benefit from the statistics so plan choice may be poor.




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