Details
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Type:
Bug
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Status: Closed
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Priority:
Major
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Resolution: Fixed
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Affects Version/s: 5.5.28
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Fix Version/s: 5.5.29
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Component/s: None
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Labels:None
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Environment:Linux x64
Description
A view which access an information schema table seems to use another plan, than the query in its extend explain output (it scan's all databases)
CREATE VIEW v1 AS SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS;
explain extended select column_name FROM v1 WHERE TABLE_SCHEMA="osm" AND TABLE_NAME="test";
extra: Using where; Open_frm_only; Scanned all databases
show warnings;
..
select `information_schema`.`COLUMNS`.`COLUMN_NAME` AS `COLUMN_NAME` from `INFORMATION_SCHEMA`.`COLUMNS` where ((`information_schema`.`COLUMNS`.`TABLE_SCHEMA` = 'osm') and (`information_schema`.`COLUMNS`.`TABLE_NAME` = 'test'))
explain select `information_schema`.`COLUMNS`.`COLUMN_NAME` AS `COLUMN_NAME` from `INFORMATION_SCHEMA`.`COLUMNS` where ((`information_schema`.`COLUMNS`.`TABLE_SCHEMA` = 'osm') and (`information_schema`.`COLUMNS`.`TABLE_NAME` = 'test'));
extra: Using where; Open_frm_only; Scanned 0 databases
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- Review discussion with Sanja, some more tests, approved by Sanja
- Merged into latest 5.5, pushed
The problem is present in MySQL 5.6.7 as well.