Details
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Bug
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Status: Closed (View Workflow)
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Critical
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Resolution: Fixed
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None
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None
Description
The following EXPLAIN EXTENDED statement produces different number of warning in case it is executed as a regular statement or as a prepared statement. In the later case one extra warning is generated.
CREATE TABLE t1 (c int);
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CREATE TABLE t2 (d int);
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EXPLAIN EXTENDED SELECT (SELECT 1 FROM t2 WHERE d = c) FROM t1;
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| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | PRIMARY | t1 | ALL | NULL | NULL | NULL | NULL | 1 | 100.00 | |
| 2 | DEPENDENT SUBQUERY | t2 | ALL | NULL | NULL | NULL | NULL | 1 | 100.00 | Using where |
2 rows in set, 2 warnings (0,020 sec)
^^^^^^^^ 2 Warnings produced
SHOW WARNINGS;
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| Level | Code | Message |
|---|---|---|
| Note | 1276 | Field or reference 'test.t1.c' of SELECT #2 was resolved in SELECT #1 |
| Note | 1003 | select <expr_cache><`test`.`t1`.`c`>((select 1 from `test`.`t2` where `test`.`t2`.`d` = `test`.`t1`.`c`)) AS `(SELECT 1 FROM t2 WHERE d = c)` from `test`.`t1` |
PREPARE stmt FROM "EXPLAIN EXTENDED SELECT (SELECT 1 FROM t2 WHERE d = c) FROM t1";
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EXECUTE stmt;
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| id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra |
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | PRIMARY | t1 | ALL | NULL | NULL | NULL | NULL | 1 | 100.00 | |
| 2 | DEPENDENT SUBQUERY | t2 | ALL | NULL | NULL | NULL | NULL | 1 | 100.00 | Using where |
2 rows in set, 3 warnings (0,001 sec)
^^^^^^^^ 3 Warnings produced (1 extra warning)
SHOW WARNINGS;
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| Level | Code | Message |
|---|---|---|
| Note | 1276 | Field or reference 'c' of SELECT #2 was resolved in SELECT #1 |
| Note | 1276 | Field or reference 'test.t1.c' of SELECT #2 was resolved in SELECT #1 |
| Note | 1003 | select <expr_cache><`test`.`t1`.`c`>((select 1 from `test`.`t2` where `test`.`t2`.`d` = `test`.`t1`.`c`)) AS `(SELECT 1 FROM t2 WHERE d = c)` from `test`.`t1` |
The same behavior (one extra warning generated in case the statement executed in PS mode) can be observed if the following test case is run:
CREATE TABLE t1 (a INT, b INT);
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EXPLAIN EXTENDED SELECT * FROM t1 WHERE a IN (SELECT a FROM t1 AS x1 WHERE (t1.b IS NULL));
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PREPARE stmt FROM "EXPLAIN EXTENDED SELECT * FROM t1 WHERE a IN (SELECT a FROM t1 AS x1 WHERE (t1.b IS NULL))";
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EXECUTE stmt;
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Attachments
Issue Links
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MDEV-16708 Unsupported commands for prepared statements
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- Closed
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