Details
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Type:
Bug
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Status: Closed
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Priority:
Minor
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Resolution: Fixed
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Affects Version/s: None
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Fix Version/s: 10.0.0
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Component/s: None
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Labels:None
Description
For the following query, and many others
SELECT a + SLEEP(0.5) FROM v1
standard EXPLAIN with the default optimizer_switch produces the following plan:
id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2 2 DERIVED t1 ALL NULL NULL NULL NULL 2
SHOW EXPLAIN sometimes returns the same briefly at the beginning, but quickly loses the 'DERIVED' line:
id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY <derived2> ALL NULL NULL NULL NULL 2
DERIVED line might be at the end of the output or in the middle, it happens anyway.
Reproducible with MyISAM, Aria, InnoDB.
bzr version-info
revision-id: psergey@askmonty.org-20120524182239-gq6jtnnovydnthtl date: 2012-05-24 22:22:39 +0400 revno: 3405
Test case:
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2);
CREATE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
--connect (con1,localhost,root,,)
let $con_id = `SELECT CONNECTION_ID()`;
EXPLAIN SELECT a + SLEEP(0.5) FROM v1;
--send
SELECT a + SLEEP(0.5) FROM v1;
--connection default
let $fail = 100;
while ($fail)
{
--error 0,ER_ERROR_WHEN_EXECUTING_COMMAND
--eval SHOW EXPLAIN FOR $con_id
--dec $fail
if (!$mysql_errno)
{
let $fail = 0;
}
}
let $pass = 5;
while ($pass)
{
--error 0,ER_ERROR_WHEN_EXECUTING_COMMAND
--eval SHOW EXPLAIN FOR $con_id
--dec $pass
if ($mysql_errno)
{
let $pass = 0;
}
}
--connection con1
--disable_result_log
--reap
Gliffy Diagrams
Attachments
Issue Links
- relates to
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MDEV-165 MWL#182: Explain running statements: finish coding, submit for review
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- Closed
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