[jira] [Created] (TRAFODION-321) LP Bug: 1324303 - bad cardinality estimates for metadata queries

["Alice Chen (JIRA)" <ji...@apache.org>]

Alice Chen created TRAFODION-321:
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             Summary: LP Bug: 1324303 - bad cardinality estimates for metadata queries
                 Key: TRAFODION-321
                 URL: https://issues.apache.org/jira/browse/TRAFODION-321
             Project: Apache Trafodion
          Issue Type: Bug
          Components: sql-cmp
            Reporter: Apache Trafodion
            Assignee: Apache Trafodion
            Priority: Critical


cardinality estimation for metadata queries is not correct. Specifically for the case of an index join and the join is on the index column. The cardinality of the join should reflect that of the left child of the join.

Example of a metadata table that has the issue:

prepare st1 from select T.CONSTRAINT_TYPE, o.OBJECT_NAME  from trafodion."_MD_".table_constraints T,  trafodion."_MD_".objects O  where T.table_uid = o.object_uid;

>>explain options 'f' st1;

LC   RC   OP   OPERATOR              OPT       DESCRIPTION           CARD
---- ---- ---- --------------------  --------  --------------------  ---------

3    .    4    root                                                  5.00E+003
2    1    3    hybrid_hash_join                                      5.00E+003
.    .    2    trafodion_index_scan            OBJECTS               1.00E+002
.    .    1    trafodion_scan                  TABLE_CONSTRAINTS     1.00E+002

--- SQL operation complete.
>>
Assigned to LaunchPad User taoufik ben abdellatif



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