Details
-
Bug
-
Status: Closed (View Workflow)
-
Minor
-
Resolution: Fixed
-
None
-
None
-
None
Description
From IRC:
<igor> elenst: could you come up with the test case where e.g. mysql.stat_table is corrupted somehow, then we 1) flush table t1; 2) set use_stat_tables='preferably' 3) run explain select * from t1;
<igor> elenst: in this case the result of explain is expected the same as we do not use ant stat tables (+ some warning).
<igor> elenst: I'm afraid now we just have rows == 0 in the explain output with this scenario, which not correct of course.
The provided test case confirms the suspicion: EXPLAIN shows 0 rows while the real number is 2.
Test case
# Run as perl ./mtr <testname>
|
|
|
CREATE TABLE t1 (i INT) ENGINE=MyISAM;
|
INSERT INTO t1 VALUES (1),(2);
|
--move_file $MYSQLTEST_VARDIR/mysqld.1/data/mysql/table_stat.MYD $MYSQLTEST_VARDIR/mysqld.1/data/mysql/table_stat.MYD.save
|
|
|
FLUSH TABLES;
|
SET use_stat_tables=PREFERABLY;
|
|
|
EXPLAIN SELECT * FROM t1;
|
|
|
# Cleanup
|
--move_file $MYSQLTEST_VARDIR/mysqld.1/data/mysql/table_stat.MYD.save $MYSQLTEST_VARDIR/mysqld.1/data/mysql/table_stat.MYD
|
|
|
SET use_stat_tables=DEFAULT;
|
DROP TABLE t1;
|
Actual result:
CREATE TABLE t1 (i INT) ENGINE=MyISAM;
|
INSERT INTO t1 VALUES (1),(2);
|
FLUSH TABLES;
|
SET use_stat_tables=PREFERABLY;
|
EXPLAIN SELECT * FROM t1;
|
id select_type table type possible_keys key key_len ref rows Extra
|
1 SIMPLE t1 ALL NULL NULL NULL NULL 0
|
Warnings:
|
Error 29 File './mysql/table_stat.MYD' not found (Errcode: 2)
|
Error 1017 Can't find file: 'table_stat' (errno: 2)
|
SET use_stat_tables=DEFAULT;
|
DROP TABLE t1;
|
bzr version-info
revision-id: elenst@ubuntu11.home-20120903180152-r1n87m6pcvzffh63
|
date: 2012-09-03 22:01:52 +0400
|
build-date: 2012-09-09 01:58:25 +0300
|
revno: 3367
|
Workaround: if EXPLAIN produces warnings about corrupted stat tables, set use_stat_tables to NEVER.