David Wayne Birdsall created TRAFODION-3151:
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Summary: Improve CQDs in UPDATE STATISTICS for using a backing
sample table
Key: TRAFODION-3151
URL: https://issues.apache.org/jira/browse/TRAFODION-3151
Project: Apache Trafodion
Issue Type: Improvement
Components: sql-cmp
Reporter: David Wayne Birdsall
Assignee: David Wayne Birdsall
In UPDATE STATISTICS, it may sometimes be desirable to manually create a sample
table and ask UPDATE STATISTICS to use that when generating statistics for a
given base table. This desire might arise from the need to work around some bug
in UPDATE STATISTICS in its own automatic sample table logic. Or the desire may
come from the need to manually manipulate the sample data itself.
There are two CQDs presently for this purpose.
CQD USTAT_SAMPLE_TABLE_NAME if set provides a table name which will be assumed
to be a user-created sample table.
CQD USTAT_USE_BACKING_SAMPLE if set to 'ON' indicates that the sample table is
a Hive table.
We could simplify this by getting rid of the second CQD, and relying on catalog
and schema qualifiers in the first CQD to indicate whether the table is Hive or
not using the usual rules (that is, if the catalog name is 'HIVE', then it is a
Hive table).
There is other logic associated with these CQDs that tries to infer sampling
ratio. This logic is inconsistent and appears incorrect. So, this aspect should
be re-engineered as needed and then appropriately documented.
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