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Posted to issues@trafodion.apache.org by "Alice Chen (JIRA)" <ji...@apache.org> on 2015/07/22 20:18:37 UTC
[jira] [Created] (TRAFODION-896) LP Bug: 1411472 - salt key
histogram not requested by optimizer
Alice Chen created TRAFODION-896:
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Summary: LP Bug: 1411472 - salt key histogram not requested by optimizer
Key: TRAFODION-896
URL: https://issues.apache.org/jira/browse/TRAFODION-896
Project: Apache Trafodion
Issue Type: Bug
Components: sql-cmp
Reporter: Julie Thai
Assignee: Barry Fritchman
Priority: Critical
Fix For: 1.1 (pre-incubation)
Histogram for salt column is not requested by optimizer.
As per Qifan, primary key is (colkey1, colkey2). if the predicate is n the second key column, then salt column stats may be useful to figure out the MDAM plan.
SQL>prepare XX from select *
from TBLX where colkey2 = 1000;
*** WARNING[6011] Statistics for column (COLKEY1) from table TRAFODION.UPDATESTATS_AUTO.TBLX were not available. As a result, the access path chosen might not be the best possible. These statistics will be automatically generated at the next opportunity; however, you can generate them now by using UPDATE STATISTICS FOR TABLE TRAFODION.UPDATESTATS_AUTO.TBLX ON NECESSARY COLUMNS. [2014-12-23 18:21:20]
*** WARNING[6011] Statistics for column (COLKEY2) from table TRAFODION.UPDATESTATS_AUTO.TBLX were not available. As a result, the access path chosen might not be the best possible. These statistics will be automatically generated at the next opportunity; however, you can generate them now by using UPDATE STATISTICS FOR TABLE TRAFODION.UPDATESTATS_AUTO.TBLX ON NECESSARY COLUMNS. [2014-12-23 18:21:20]
--- SQL command prepared.
SQL>execute show_hist;
(EXPR) READ_TIME READ_COUNT REASON
--------------------------------------------- ------------------- ---------- ------
TBLX.COLKEY1 0001-01-01 00:00:00 0
TBLX.COLKEY2 0001-01-01 00:00:00 0
--- 2 row(s) selected.
SQL>update statistics for
table TBLX on necessary columns;
--- SQL operation complete.
SQL>execute show_hist;
(EXPR) READ_TIME READ_COUNT REASON
--------------------------------------------- ------------------- ---------- ------
TBLX.COLKEY1 0001-01-01 00:00:00 0 I
TBLX.COLKEY2 0001-01-01 00:00:00 0 I
--- 2 row(s) selected.
As per Barry:
prepare s from select o_custkey from orders where o_shippriority > 2;
histograms for both o_orderkey (primary key) and o_shippriority are requested.
prepare s from select o_custkey from orders where "_SALT_">2;
only o_orderkey histogram was requested.
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