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From:Jorgen Loland Date:April 15 2011 8:29am
Subject:bzr commit into mysql-5.5 branch (jorgen.loland:3448) Bug#11765699
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#At file:///export/home/jl208045/mysql/mysql-5.5-11765699/ based on revid:serge.kozlov@stripped

 3448 Jorgen Loland	2011-04-15
      Bug#11765699 - 58690: !TABLE || 
      (!TABLE->READ_SET || BITMAP_IS_SET(TABLE->READ_SET, FIELD_INDEX
      
      JOIN::conds points to the same expression tree as SELECT_LEX::where, so
      modifying the expression tree of JOIN::conds effectively does the same
      modifications to SELECT_LEX::where.
      
      JOIN::conds is optimized in JOIN::optimize()
      
        conds= optimize_cond(conds);
      
      optimize_cond() makes modifications to the conds input parameter. One 
      of these modifications removes an item from the input conds parameter. 
      This was not a problem for JOIN::conds because removed items are 
      included in the condition returned from the function and therefore 
      assigned to conds as can be seen above. However, the removed parts of 
      the condition were lost from SELECT_LEX::where.
      
      This bug was about a query with three levels of subselects:
      
      SELECT 1 FROM t1 WHERE a = 
      (SELECT 1 FROM t2 WHERE b = 
      (SELECT 1 FROM t1 t11 WHERE c = 1 OR t1.a = 1 AND 1 = 2)
      GROUP BY b
      );
      
      Prior to optimization, select#3 has 
      
      join->conds = select_lex->where = "c = 1 OR t1.a = 1 AND 1 = 2"
      
      As part of optimize_cond(), remove_eq_conds() sees that 
      "t1.a = 1 AND 1 = 2" is FALSE and correctly removes this condition. This
      leaves the OR item with only one argument: "c = 1". With only one
      argument left in this OR, internal_remove_eq_conds() empties the argument
      list of the OR and returns "c = 1". The effect is that after 
      optimize_cond(), select#3 has:
      
      join->conds = "c = 1"
      select_lex->where = ""   // <- !!
      
      Fixed by not emptying the argument list of an Item_cond even when there 
      is only one argument. The effect is that after optimize_cond(),
      select_lex->where is an OR-item with only one argument: "c = 1". This is
      slightly inefficient (evaluation would have to go through the OR), but 
      it works correctly. Note that condition evaluation is performed using the 
      correctly optimized JOIN::conds.
      
      Note: This fix has to be reconsidered when the optimizer has been split 
      into separate phases.
     @ mysql-test/r/subselect_innodb.result
        Added test for BUG#11765699
     @ mysql-test/t/subselect_innodb.test
        Added test for BUG#11765699
     @ sql/sql_select.cc
        In internal_remove_eq_conds(): Do not empty argument_list() of an Item_cond
        with only one argument. This will result in lost condition parts in 
        SELECT_LEX::where/having

    modified:
      mysql-test/r/subselect_innodb.result
      mysql-test/t/subselect_innodb.test
      sql/sql_select.cc
=== modified file 'mysql-test/r/subselect_innodb.result'
--- a/mysql-test/r/subselect_innodb.result	2011-02-17 12:41:25 +0000
+++ b/mysql-test/r/subselect_innodb.result	2011-04-15 08:29:20 +0000
@@ -254,3 +254,21 @@ SELECT * FROM t1 WHERE b < (SELECT CAST(
 a	b
 2011-05-13	0
 DROP TABLE t1;
+#
+# Bug 11765699 - 58690: !TABLE || (!TABLE->READ_SET || 
+#                BITMAP_IS_SET(TABLE->READ_SET, FIELD_INDEX
+#
+CREATE TABLE t1( a INT );
+INSERT INTO t1 VALUES (0), (1);
+CREATE TABLE t2( b TEXT, c INT, PRIMARY KEY (b( 1 )) ) ENGINE = INNODB;
+INSERT INTO t2 VALUES ('a', ''), ('b', '');
+Warnings:
+Warning	1366	Incorrect integer value: '' for column 'c' at row 1
+Warning	1366	Incorrect integer value: '' for column 'c' at row 2
+SELECT 1 FROM t1 WHERE a = 
+(SELECT 1 FROM t2 WHERE b = 
+(SELECT 1 FROM t1 t11 WHERE c = 1 OR t1.a = 1 AND 1 = 2)
+GROUP BY b
+);
+1
+DROP TABLE t1, t2;

=== modified file 'mysql-test/t/subselect_innodb.test'
--- a/mysql-test/t/subselect_innodb.test	2011-02-17 12:41:25 +0000
+++ b/mysql-test/t/subselect_innodb.test	2011-04-15 08:29:20 +0000
@@ -247,3 +247,22 @@ CREATE TABLE t1(a date, b int, unique(b)
 INSERT INTO t1 VALUES ('2011-05-13', 0);
 SELECT * FROM t1 WHERE b < (SELECT CAST(a as date) FROM t1 GROUP BY a); 
 DROP TABLE t1;
+
+--echo #
+--echo # Bug 11765699 - 58690: !TABLE || (!TABLE->READ_SET || 
+--echo #                BITMAP_IS_SET(TABLE->READ_SET, FIELD_INDEX
+--echo #
+
+CREATE TABLE t1( a INT );
+INSERT INTO t1 VALUES (0), (1); 
+
+CREATE TABLE t2( b TEXT, c INT, PRIMARY KEY (b( 1 )) ) ENGINE = INNODB;
+INSERT INTO t2 VALUES ('a', ''), ('b', '');
+
+SELECT 1 FROM t1 WHERE a = 
+ (SELECT 1 FROM t2 WHERE b = 
+  (SELECT 1 FROM t1 t11 WHERE c = 1 OR t1.a = 1 AND 1 = 2)
+   GROUP BY b
+ );
+
+DROP TABLE t1, t2;

=== modified file 'sql/sql_select.cc'
--- a/sql/sql_select.cc	2011-04-14 09:10:11 +0000
+++ b/sql/sql_select.cc	2011-04-15 08:29:20 +0000
@@ -919,6 +919,13 @@ JOIN::optimize()
       thd->restore_active_arena(arena, &backup);
   }
 
+  /*
+    Note: optimize_cond makes changes to conds. Since
+    select_lex->where and conds points to the same condition, this
+    function call effectively changes select_lex->where as well. This
+    needs to be reconsidered after splitting the optimizer into
+    properly separated phases.
+  */
   conds= optimize_cond(this, conds, join_list, &cond_value);   
   if (thd->is_error())
   {
@@ -928,6 +935,7 @@ JOIN::optimize()
   }
 
   {
+    // Note above about optimize_cond also applies to SELEC_LEX->having
     having= optimize_cond(this, having, join_list, &having_value);
     if (thd->is_error())
     {
@@ -9441,7 +9449,8 @@ optimize_cond(JOIN *join, COND *conds, L
   SYNPOSIS
     remove_eq_conds()
     thd 			THD environment
-    cond                        the condition to handle
+    cond                        the condition to handle. Note that cond
+                                is changed by this function
     cond_value                  the resulting value of the condition
 
   RETURN
@@ -9503,9 +9512,34 @@ internal_remove_eq_conds(THD *thd, COND 
 	*cond_value != Item::COND_OK)
       return (COND*) 0;
     if (((Item_cond*) cond)->argument_list()->elements == 1)
-    {						// Remove list
+    {
+      /*
+        BUG#11765699:
+        We're dealing with an AND or OR item that has only one
+        argument. However, it is not an option to empty the list
+        because:
+
+         - this function is called for either JOIN::conds or
+           JOIN::having, but these point to the same condition as
+           SELECT_LEX::where and SELECT_LEX::having do.
+
+         - The return value of remove_eq_conds() is assigned to
+           JOIN::conds and JOIN::having, so emptying the list and
+           returning the only remaining item "replaces" the AND or OR
+           with item for the variables in JOIN. However, the return
+           value is not assigned to the SELECT_LEX counterparts. Thus,
+           if argument_list is emptied, SELECT_LEX forgets the item in
+           argument_list()->head().
+
+        item is therefore returned, but argument_list is not emptied.
+      */
       item= ((Item_cond*) cond)->argument_list()->head();
-      ((Item_cond*) cond)->argument_list()->empty();
+      /*
+        Consider reenabling the line below when the optimizer has been
+        split into properly separated phases.
+ 
+        ((Item_cond*) cond)->argument_list()->empty();
+      */
       return item;
     }
   }


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bzr commit into mysql-5.5 branch (jorgen.loland:3448) Bug#11765699Jorgen Loland15 Apr
  • Re: bzr commit into mysql-5.5 branch (jorgen.loland:3448) Bug#11765699Roy Lyseng27 Apr