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From:Evgeny Potemkin Date:October 27 2008 9:26am
Subject:bzr commit into mysql-5.1 branch (epotemkin:2765) Bug#37870
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#At file:///work/bzr_trees/37870-bug-5.1-bugteam/

 2765 Evgeny Potemkin	2008-10-27
      Bug#37870: Usage of uninitialized value caused failed assertion.
            
      The convert_constant_item function converts a constant to integer using
      field for condition like 'field = a_constant'. When the convert_constant_item
      is called for a subquery the outer select is already being executed, so
      convert_constant_item saves field's value to prevent its corruption.
      For EXPLAIN field's value isn't initialized thus when convert_constant_item
      tries to restore saved value it fails assertion.
            
      Now the convert_constant_item doesn't save/restore field's value
      for EXPLAIN.
modified:
  mysql-test/r/explain.result
  mysql-test/t/explain.test
  sql/item_cmpfunc.cc

per-file messages:
  mysql-test/r/explain.result
    Added a test case for the bug#37870.
  mysql-test/t/explain.test
    Added a test case for the bug#37870.
  sql/item_cmpfunc.cc
    Bug#37870: Usage of uninitialized value caused failed assertion.
    Now the convert_constant_item doesn't save/restore field's value
    for EXPLAIN.
=== modified file 'mysql-test/r/explain.result'
--- a/mysql-test/r/explain.result	2007-11-16 11:00:57 +0000
+++ b/mysql-test/r/explain.result	2008-10-27 09:26:32 +0000
@@ -107,3 +107,18 @@ X	X	X	X	X	X	X	X	X	
 X	X	X	X	X	X	X	X	X	Range checked for each record (index map: 0xFFFFFFFFFF)
 DROP TABLE t2;
 DROP TABLE t1;
+#
+# Bug#37870: Usage of uninitialized value caused failed assertion.
+#
+create table t1 (dt datetime not null);
+create table t2 (dt datetime not null);
+insert into t1 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');
+insert into t2 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');
+flush tables;
+EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	OUTR	ALL	NULL	NULL	NULL	NULL	2	Using where
+2	DEPENDENT SUBQUERY	INNR	ALL	NULL	NULL	NULL	NULL	2	Using where
+SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );
+dt
+drop tables t1, t2;

=== modified file 'mysql-test/t/explain.test'
--- a/mysql-test/t/explain.test	2007-11-16 11:00:57 +0000
+++ b/mysql-test/t/explain.test	2008-10-27 09:26:32 +0000
@@ -94,4 +94,16 @@ EXPLAIN SELECT 1 FROM
 DROP TABLE t2;
 DROP TABLE t1;
 
+--echo #
+--echo # Bug#37870: Usage of uninitialized value caused failed assertion.
+--echo #
+create table t1 (dt datetime not null);
+create table t2 (dt datetime not null);
+insert into t1 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');
+insert into t2 values ('2001-01-01 1:1:1'), ('2001-01-01 1:1:1');
+flush tables;
+EXPLAIN SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );
+SELECT OUTR.dt FROM t1 AS OUTR WHERE OUTR.dt IN (SELECT INNR.dt FROM t2 AS INNR WHERE OUTR.dt IS NULL );
+drop tables t1, t2;
+
 # End of 5.0 tests.

=== modified file 'sql/item_cmpfunc.cc'
--- a/sql/item_cmpfunc.cc	2008-09-09 15:52:38 +0000
+++ b/sql/item_cmpfunc.cc	2008-10-27 09:26:32 +0000
@@ -415,8 +415,9 @@ static bool convert_constant_item(THD *t
     /*
       Store the value of the field if it references an outer field because
       the call to save_in_field below overrides that value.
+      Don't store it for EXPLAIN since it's not initialized.
     */
-    if (field_item->depended_from)
+    if (field_item->depended_from && !thd->lex->describe)
       orig_field_val= field->val_int();
     if (!(*item)->is_null() && !(*item)->save_in_field(field, 1))
     {
@@ -427,7 +428,7 @@ static bool convert_constant_item(THD *t
       result= 1;					// Item was replaced
     }
     /* Restore the original field value. */
-    if (field_item->depended_from)
+    if (field_item->depended_from && !thd->lex->describe)
     {
       result= field->store(orig_field_val, TRUE);
       /* orig_field_val must be a valid value that can be restored back. */

Thread
bzr commit into mysql-5.1 branch (epotemkin:2765) Bug#37870Evgeny Potemkin27 Oct