bk commit into 4.1 tree (timour:1.2304) BUG#11185

[timour]

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ChangeSet
  1.2304 05/06/23 10:56:44 timour@stripped +3 -0
  Fix for BUG#11185.
  
  The source of the problem is in Field_longlong::cmp. If 'this' is
  an unsigned number, the method casts both the current value, and
  the constant that we compare with to an unsigned number. As a
  result if the constant we compare with is a negative number, it
  wraps to some unsigned number, and the comparison is incorrect.
  
  When the optimizer chooses the "range" access method, this problem
  causes handler::read_range_next to reject the current key when the
  upper bound key is a negative number because handler::compare_key
  incorrectly considers the positive and negative keys to be equal.
  
  The current patch does not correct the source of the problem in
  Field_longlong::cmp because it is not easy to propagate sign
  information about the constant at query execution time. Instead
  the patch changes the range optimizer so that it never compares
  unsiged fields with negative constants. As an added benefit,
  queries that do such comparisons will execute faster because
  the range optimizer replaces conditions like:
  (a) (unsigned_int [< | <=] negative_constant) == FALSE
  (b) (unsigned_int [> | >=] negative_constant) == TRUE
  with the corresponding constants.
  In some cases this may even result in constant time execution.

  sql/opt_range.cc
    1.139 05/06/23 10:56:39 timour@stripped +35 -3
    Added a new optimization to the range optimizer where we detect that
    an UNSIGNED field is compared with a negative constant. Depending on
    the comparison operator, we know directly that the result of the
    comparison is either TRUE or FALSE for all input values, and we need
    not check each value.
    
    This optimization is also necessary so that the index range access
    method produces correct results when comparing unsigned fields with
    negative constants.

  mysql-test/t/range.test
    1.29 05/06/23 10:56:39 timour@stripped +19 -3
    - Added new tests for BUG#11185
    - Deleted an old comment because now the problem is fixed

  mysql-test/r/range.result
    1.34 05/06/23 10:56:39 timour@stripped +32 -1
    - Changed incorrect result of an old test
    - Added new results for BUG#11185

# This is a BitKeeper patch.  What follows are the unified diffs for the
# set of deltas contained in the patch.  The rest of the patch, the part
# that BitKeeper cares about, is below these diffs.
# User:	timour
# Host:	zmei.home
# Root:	/home/timka/mysql/src/4.1-bug-11185

--- 1.138/sql/opt_range.cc	2005-06-05 20:38:41 +03:00
+++ 1.139/sql/opt_range.cc	2005-06-23 10:56:39 +03:00
@@ -960,7 +960,9 @@
 	if (sel_arg->type == SEL_ARG::IMPOSSIBLE)
 	{
 	  tree->type=SEL_TREE::IMPOSSIBLE;
-	  DBUG_RETURN(tree);
+          /* If this is an NE_FUNC, we still need to check GT_FUNC. */
+          if (!ne_func)
+            DBUG_RETURN(tree);
 	}
       }
       else
@@ -979,8 +981,9 @@
     SEL_TREE *tree2= get_mm_parts(param, cond_func,
 				  field, Item_func::GT_FUNC,
                                   value, cmp_type);
-    if (tree2)
-      tree= tree_or(param,tree,tree2);
+    if (!tree2)
+      DBUG_RETURN(0)
+    tree= tree_or(param,tree,tree2);
   }
   DBUG_RETURN(tree);
 }
@@ -1158,6 +1161,35 @@
   }
   if (!(tree=new SEL_ARG(field,str,str2)))
     DBUG_RETURN(0);		// out of memory
+
+  /*
+    Check if we are comparing an UNSIGNED integer with a negative constant.
+    In this case we know that:
+    (a) (unsigned_int [< | <=] negative_constant) == FALSE
+    (b) (unsigned_int [> | >=] negative_constant) == TRUE
+    In case (a) the condition is false for all values, and in case (b) it
+    is true for all values, so we can avoid unnecessary retrieval and condition
+    testing, and we also get correct comparison of unsinged integers with
+    negative integers (which otherwise fails because at query execution time
+    negative integers are cast to unsigned if compared with unsigned).
+   */
+  Item_result field_result_type= field->result_type();
+  Item_result value_result_type= value->result_type();
+  if (field_result_type == INT_RESULT && value_result_type == INT_RESULT
&&
+      ((Field_num*)field)->unsigned_flag &&
!((Item_int*)value)->unsigned_flag)
+  {
+    longlong item_val= value->val_int();
+    if (item_val < 0)
+    {
+      if (type == Item_func::LT_FUNC || type == Item_func::LE_FUNC)
+      {
+        tree->type= SEL_ARG::IMPOSSIBLE;
+        DBUG_RETURN(tree);
+      }
+      if (type == Item_func::GT_FUNC || type == Item_func::GE_FUNC)
+        DBUG_RETURN(0);
+    }
+  }
 
   switch (type) {
   case Item_func::LT_FUNC:

--- 1.33/mysql-test/r/range.result	2005-04-17 01:05:06 +03:00
+++ 1.34/mysql-test/r/range.result	2005-06-23 10:56:39 +03:00
@@ -556,10 +556,41 @@
 0
 select count(*) from t1 where x > -16;
 count(*)
-1
+2
 select count(*) from t1 where x = 18446744073709551601;
 count(*)
 1
+drop table t1;
+create table t1 (a bigint unsigned);
+create index t1i on t1(a);
+insert into t1 select 18446744073709551615;
+insert into t1 select 18446744073709551614;
+explain select * from t1 where a <> -1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	t1i	t1i	9	NULL	2	Using where; Using index
+select * from t1 where a <> -1;
+a
+18446744073709551614
+18446744073709551615
+explain select * from t1 where a > -1 or a < -1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	t1i	t1i	9	NULL	2	Using where; Using index
+select * from t1 where a > -1 or a < -1;
+a
+18446744073709551614
+18446744073709551615
+explain select * from t1 where a > -1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index	t1i	t1i	9	NULL	2	Using where; Using index
+select * from t1 where a > -1;
+a
+18446744073709551614
+18446744073709551615
+explain select * from t1 where a < -1;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const
tables
+select * from t1 where a < -1;
+a
 drop table t1;
 set names latin1;
 create table t1 (a char(10), b text, key (a)) character set latin1;

--- 1.28/mysql-test/t/range.test	2005-05-18 12:02:52 +03:00
+++ 1.29/mysql-test/t/range.test	2005-06-23 10:56:39 +03:00
@@ -423,11 +423,27 @@
 select count(*) from t1 where x<0;
 select count(*) from t1 where x < -16;
 select count(*) from t1 where x = -16;
-# The following query returns wrong value because the range optimizer can't
-# handle search on a signed value for an unsigned parameter. This will be fixed in
-# 5.0
 select count(*) from t1 where x > -16;
 select count(*) from t1 where x = 18446744073709551601;
+
+drop table t1;
+
+#
+# Bug #11185 incorrect comparison of unsigned int to signed constant
+#
+create table t1 (a bigint unsigned);
+create index t1i on t1(a);
+insert into t1 select 18446744073709551615;
+insert into t1 select 18446744073709551614;
+
+explain select * from t1 where a <> -1;
+select * from t1 where a <> -1;
+explain select * from t1 where a > -1 or a < -1;
+select * from t1 where a > -1 or a < -1;
+explain select * from t1 where a > -1;
+select * from t1 where a > -1;
+explain select * from t1 where a < -1;
+select * from t1 where a < -1;
 
 drop table t1;