Details
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Sub-Task
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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None
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None
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2021-4
Description
This task is similar to MCOL-4543, but for subqueries involving a UNION. I.e., If query Q1 is of the form:
SELECT count(c2) FROM (SELECT * FROM t1 UNION ALL SELECT * FROM t1)q; |
Assuming t1 here contains 10 columns c1, c2, ... , c10. We build an ineffective RowGroup in ExeMgr of the form (1, c2_value1, 1, 1, 1, 1, 1, 1, 1, 1). The objective here is to remove all non-referenced columns from the end, until the first referenced column is encountered, i.e. trim down the RowGroup to (1, c2_value1).
Build verified: 5.6.1 ( Drone #2207 )
Tested on a 1gb dbt3 database
5.5.2-1
MariaDB [tpch1]> SELECT count(l_orderkey) FROM (SELECT * FROM lineitem UNION ALL SELECT * FROM lineitem) q;+-------------------+| count(l_orderkey) |+-------------------+| 12002430 |+-------------------+1 row in set (7.106 sec)5.6.1
MariaDB [tpch1]> SELECT count(l_orderkey) FROM (SELECT * FROM lineitem UNION ALL SELECT * FROM lineitem) q;+-------------------+| count(l_orderkey) |+-------------------+| 12002430 |+-------------------+1 row in set (1.731 sec)