From: Jorgen Loland
Date: September 26 2011 1:48pm
Subject: bzr push into mysql-trunk branch (jorgen.loland:3437 to 3438) Bug#12837714
List-Archive: http://lists.mysql.com/commits/141142
X-Bug: 12837714
Message-Id: <20110926134824.400B26B7@atum21.no.oracle.com>
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 3438 Jorgen Loland	2011-09-26
      BUG#12837714: ADDITIONAL NULL IN 5.6 ON GROUPED SELECT
      
      The bug was that Cached_item_field::cmp() did not do proper 
      NULL checking: if both buff and the field values were NULL, 
      the result was based on bitwise field comparison. Since a 
      field with NULL value may contain random bits, buff and 
      field were considered different in this case.
      
      The fix is to handle the case where both are NULL: the 
      returned value from the function is now that they are equal.
      
      Note: there are four more Cached_item_* classes: For the int,
      real and decimal versions it is OK to compare cached value 
      to the new value because val_int/decimal/real() return 0 if 
      the value is NULL. For the string cached item, we get the 
      same issue as with Cached_item_field but for this class the 
      case where cached value and new value are both NULL is already 
      handled.
     @ mysql-test/r/group_by.result
        Add regression test for bug 12837714
     @ mysql-test/t/group_by.test
        Add regression test for bug 12837714
     @ sql/item_buff.cc
        Fixed Cached_item_field::cmp() to handle the case where both cached and new field value is NULL.
     @ sql/table.cc
        Remove dead code

    modified:
      mysql-test/r/group_by.result
      mysql-test/t/group_by.test
      sql/item_buff.cc
      sql/table.cc
 3437 Tor Didriksen	2011-09-26 [merge]
      merge 5.5 => trunk

    modified:
      mysql-test/r/func_str.result
      mysql-test/t/func_str.test
=== modified file 'mysql-test/r/group_by.result'
--- a/mysql-test/r/group_by.result	2011-09-13 07:22:49 +0000
+++ b/mysql-test/r/group_by.result	2011-09-26 13:48:06 +0000
@@ -2108,3 +2108,17 @@ pk
 DROP VIEW v1;
 DROP TABLE t1,t2;
 # End of Bug#12798270
+#
+# Bug#12837714: ADDITIONAL NULL IN 5.6 ON GROUPED SELECT
+#
+CREATE TABLE t1 (vc varchar(1), INDEX vc_idx (vc)) ;
+INSERT INTO t1 VALUES (NULL), ('o'), (NULL), ('p'), ('c');
+FLUSH TABLE t1;
+SELECT vc FROM t1 GROUP BY vc;
+vc
+NULL
+c
+o
+p
+DROP TABLE t1;
+# End of Bug#12837714

=== modified file 'mysql-test/t/group_by.test'
--- a/mysql-test/t/group_by.test	2011-08-30 09:01:05 +0000
+++ b/mysql-test/t/group_by.test	2011-09-26 13:48:06 +0000
@@ -1468,3 +1468,17 @@ DROP TABLE t1,t2;
 
 --echo # End of Bug#12798270
 
+--echo #
+--echo # Bug#12837714: ADDITIONAL NULL IN 5.6 ON GROUPED SELECT
+--echo #
+
+CREATE TABLE t1 (vc varchar(1), INDEX vc_idx (vc)) ;
+INSERT INTO t1 VALUES (NULL), ('o'), (NULL), ('p'), ('c');
+
+FLUSH TABLE t1;
+
+SELECT vc FROM t1 GROUP BY vc;
+
+DROP TABLE t1; 
+
+--echo # End of Bug#12837714

=== modified file 'sql/item_buff.cc'
--- a/sql/item_buff.cc	2011-06-30 15:50:45 +0000
+++ b/sql/item_buff.cc	2011-09-26 13:48:06 +0000
@@ -137,16 +137,34 @@ bool Cached_item_int::cmp(void)
 bool Cached_item_field::cmp(void)
 {
   DBUG_ENTER("Cached_item_field::cmp");
-  bool tmp= field->cmp(buff) != 0;		// This is not a blob!
   DBUG_EXECUTE("info", dbug_print(););
-  if (tmp)
-    field->get_image(buff,length,field->charset());
-  if (null_value != field->is_null())
+
+  bool different= false;
+
+  if (field->is_null())
+  {
+    if (!null_value)
+    {
+      different= true;
+      null_value= true;
+    }
+  }
+  else
   {
-    null_value= !null_value;
-    tmp=TRUE;
+    if (null_value)
+    {
+      different= true;
+      null_value= false;
+      field->get_image(buff, length, field->charset());
+    }
+    else if (field->cmp(buff))                  // Not a blob: cmp() is OK
+    {
+      different= true;
+      field->get_image(buff, length, field->charset());
+    }
   }
-  DBUG_RETURN(tmp);
+
+  DBUG_RETURN(different);
 }
 
 

=== modified file 'sql/table.cc'
--- a/sql/table.cc	2011-08-26 13:26:33 +0000
+++ b/sql/table.cc	2011-09-26 13:48:06 +0000
@@ -1981,9 +1981,6 @@ int open_table_from_share(THD *thd, TABL
   {
     memcpy(outparam->record[0], share->default_values, share->rec_buff_length);
     memcpy(outparam->record[1], share->default_values, share->null_bytes);
-    if (records > 2)
-      memcpy(outparam->record[1], share->default_values,
-             share->rec_buff_length);
   }
 #endif
 

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