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Bug#39843 DELETE requires write access to table in subquery in where clause

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An unnecessarily restrictive lock were taken on sub-SELECTs during DELETE.

During parsing, a global structure is reused for sub-SELECTs and the attribute
keeping track of lock options were not reset properly.
This patch introduces a new attribute to keep track on the syntactical lock
option elements found in a sub-SELECT and then sets the lock options accordingly.

Now the sub-SELECTs will try to acquire a READ lock if possible
instead of a WRITE lock as inherited from the outer DELETE statement.


mysql-test/r/lock.result:
  Added test case for bug39843
mysql-test/t/lock.test:
  Added test case for bug39843
sql/sql_lex.cc:
  * Reset member variable lock_option on each new query.
sql/sql_lex.h:
  * Introduced new member variable 'lock_option' which is keeping track
    of the syntactical lock option of a (sub-)select query.
sql/sql_parse.cc:
  * Wrote comments to functions.
sql/sql_yacc.yy:
  * Introduced an attribute to keep track of syntactical lock options
    in sub-selects.
  * Made sure that the default value TL_READ_DEFAULT is at the begining
    of each subselect-rule.
This commit is contained in:
Kristofer Pettersson
2009-03-05 15:22:33 +01:00
parent d61f114f7f
commit ddaede8087
6 changed files with 103 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

27
mysql-test/r/lock.result
View File

@ -166,4 +166,31 @@ ERROR HY000: View's SELECT refers to a temporary table 't2'
Cleanup.
drop table t2, t3;
#
# Bug#39843 DELETE requires write access to table in subquery in where clause
#
DROP TABLE IF EXISTS t1,t2;
CREATE TABLE t1 (
table1_rowid SMALLINT NOT NULL
);
CREATE TABLE t2 (
table2_rowid SMALLINT NOT NULL
);
INSERT INTO t1 VALUES (1);
INSERT INTO t2 VALUES (1);
LOCK TABLES t1 WRITE, t2 READ;
# Sub-select should not try to aquire a write lock.
DELETE FROM t1
WHERE EXISTS
(
SELECT 'x'
FROM t2
WHERE t1.table1_rowid = t2.table2_rowid
) ;
# While implementing the patch we didn't break old behavior;
# The following sub-select should still requires a write lock:
SELECT * FROM t1 WHERE 1 IN (SELECT * FROM t2 FOR UPDATE);
ERROR HY000: Table 't2' was locked with a READ lock and can't be updated
UNLOCK TABLES;
DROP TABLE t1,t2;
End of 5.1 tests.

30
mysql-test/t/lock.test
View File

@ -214,4 +214,34 @@ create view v_bug5719 as select * from t2;
--echo
drop table t2, t3;
--echo #
--echo # Bug#39843 DELETE requires write access to table in subquery in where clause
--echo #
--disable_warnings
DROP TABLE IF EXISTS t1,t2;
--enable_warnings
CREATE TABLE t1 (
table1_rowid SMALLINT NOT NULL
);
CREATE TABLE t2 (
table2_rowid SMALLINT NOT NULL
);
INSERT INTO t1 VALUES (1);
INSERT INTO t2 VALUES (1);
LOCK TABLES t1 WRITE, t2 READ;
--echo # Sub-select should not try to aquire a write lock.
DELETE FROM t1
WHERE EXISTS
(
SELECT 'x'
FROM t2
WHERE t1.table1_rowid = t2.table2_rowid
) ;
--echo # While implementing the patch we didn't break old behavior;
--echo # The following sub-select should still requires a write lock:
--error ER_TABLE_NOT_LOCKED_FOR_WRITE
SELECT * FROM t1 WHERE 1 IN (SELECT * FROM t2 FOR UPDATE);
UNLOCK TABLES;
DROP TABLE t1,t2;
--echo End of 5.1 tests.