Commit 7a11df8c authored by unknown's avatar unknown
Browse files

Fixed bug#21475: Wrongly applied constant propagation leads to a false comparison. 

A date can be represented as an int (like 20060101) and as a string (like
"2006.01.01"). When a DATE/TIME field is compared in one SELECT against both
representations the constant propagation mechanism leads to comparison
of DATE as a string and DATE as an int. In this example it compares 2006 and
20060101 integers. Obviously it fails comparison although they represents the
same date.


Now the Item_bool_func2::fix_length_and_dec() function sets the comparison
context for items being compared. I.e. if items compared as strings the
comparison context is STRING.
The constant propagation mechanism now doesn't mix items used in different
comparison contexts. The context check is done in the
Item_field::equal_fields_propagator() and in the change_cond_ref_to_const() 
functions.

Also the better fix for bug 21159 is introduced.


mysql-test/t/type_datetime.test:
  Added a test case for bug#21475: Wrongly applied constant propagation leads to a false comparison.
mysql-test/r/type_datetime.result:
  Added a test case for bug#21475: Wrongly applied constant propagation leads to a false comparison.
sql/sql_select.cc:
  Fixed bug#21475: Wrongly applied constant propagation leads to a false comparison.
  The constant propagation mechanism now doesn't mix items used in different
  comparison contexts. The check is done in the change_cond_ref_to_const() function.
sql/item_cmpfunc.cc:
  Fixed bug#21475: Wrongly applied constant propagation leads to a false comparison.
  Now the Item_bool_func2::fix_length_and_dec() function sets the comparison
  context for items being compared.
sql/item.h:
  Fixed bug#21475: Wrongly applied constant propagation leads to a false comparison.
  To the Item class a new field called cmp_context is added.
  It represents the comparison context of an item.
sql/item.cc:
  Fixed bug#21475: Wrongly applied constant propagation leads to a false comparison.
  The constant propagation mechanism now doesn't mix items used in different
  comparison contexts. The context check is done in the
  Item_field::equal_fields_propagator() function.
parent 1cbebc6e

mysql-test/r/type_datetime.result

+11 −0
Original line number Diff line number Diff line
@@ -168,3 +168,14 @@ dt 
0000-00-00 00:00:00

0000-00-00 00:00:00

drop table t1;

CREATE TABLE t1(a DATETIME NOT NULL);

INSERT INTO t1 VALUES ('20060606155555');

SELECT a FROM t1 WHERE a=(SELECT MAX(a) FROM t1) AND (a="20060606155555");

a

2006-06-06 15:55:55

PREPARE s FROM 'SELECT a FROM t1 WHERE a=(SELECT MAX(a) FROM t1) AND (a="20060606155555")';

EXECUTE s;

a

2006-06-06 15:55:55

DROP PREPARE s;

DROP TABLE t1;

mysql-test/t/type_datetime.test

+11 −0
Original line number Diff line number Diff line
@@ -114,3 +114,14 @@ select * from t1; 
drop table t1;



# End of 4.1 tests



#

# Bug#21475: Wrongly applied constant propagation leads to a false comparison.

#

CREATE TABLE t1(a DATETIME NOT NULL);

INSERT INTO t1 VALUES ('20060606155555');

SELECT a FROM t1 WHERE a=(SELECT MAX(a) FROM t1) AND (a="20060606155555");

PREPARE s FROM 'SELECT a FROM t1 WHERE a=(SELECT MAX(a) FROM t1) AND (a="20060606155555")';

EXECUTE s;

DROP PREPARE s;

DROP TABLE t1;

sql/item.cc

+12 −1
Original line number Diff line number Diff line
@@ -3777,7 +3777,18 @@ Item *Item_field::equal_fields_propagator(byte *arg) 
  Item *item= 0;

  if (item_equal)

    item= item_equal->get_const();

  if (!item)

  /*

    Disable const propagation for items used in different comparison contexts.

    This must be done because, for example, Item_hex_string->val_int() is not

    the same as (Item_hex_string->val_str() in BINARY column)->val_int().

    We cannot simply disable the replacement in a particular context (

    e.g. <bin_col> = <int_col> AND <bin_col> = <hex_string>) since

    Items don't know the context they are in and there are functions like 

    IF (<hex_string>, 'yes', 'no').

    The same problem occurs when comparing a DATE/TIME field with a

    DATE/TIME represented as an int and as a string.

  */

  if (!item || item->cmp_context != cmp_context)

    item= this;

  return item;

}

sql/item.h

+1 −1
Original line number Diff line number Diff line
@@ -465,7 +465,7 @@ class Item { 
  my_bool with_subselect;               /* If this item is a subselect or some

                                           of its arguments is or contains a

                                           subselect */



  Item_result cmp_context;              /* Comparison context */

  // alloc & destruct is done as start of select using sql_alloc

  Item();

  /*

sql/item_cmpfunc.cc

+4 −1
Original line number Diff line number Diff line
@@ -405,7 +405,8 @@ void Item_bool_func2::fix_length_and_dec() 
      agg_arg_charsets(coll, args, 2, MY_COLL_CMP_CONV, 1))

    return;

    

 

  args[0]->cmp_context= args[1]->cmp_context=

    item_cmp_type(args[0]->result_type(), args[1]->result_type());

  // Make a special case of compare with fields to get nicer DATE comparisons



  if (functype() == LIKE_FUNC)  // Disable conversion in case of LIKE function.
@@ -426,6 +427,7 @@ void Item_bool_func2::fix_length_and_dec() 
        {

          cmp.set_cmp_func(this, tmp_arg, tmp_arg+1,

                           INT_RESULT);		// Works for all types.

          args[0]->cmp_context= args[1]->cmp_context= INT_RESULT;

          return;

        }

      }
@@ -440,6 +442,7 @@ void Item_bool_func2::fix_length_and_dec() 
        {

          cmp.set_cmp_func(this, tmp_arg, tmp_arg+1,

                           INT_RESULT); // Works for all types.

          args[0]->cmp_context= args[1]->cmp_context= INT_RESULT;

          return;

        }

      }