Fixed bug #21698: erroneously a field could be replaced by an

equal constant under any circumstances.
In fact this substitution can be allowed if the field is
not of a type string or if the field reference serves as 
an argument of a comparison predicate.  


mysql-test/r/func_str.result:
  Added test cases for bug #21698.
mysql-test/r/heap_hash.result:
  Adjusted results after the fix for bug #21198.
mysql-test/t/func_str.test:
  Added test cases for bug #21698.
sql/item.cc:
  Fixed bug #21198.
  Added a method to check whether a field reference can be 
  substituted for a constant equal to the field.
  This substitution is allowed if the field is not of a type string
  or if the field reference serves as an argument of a comparison
  predicate.
sql/item.h:
  Fixed bug #21698.
  Added a new virtual transformation method for a item 'compile'
  with two callback function parameters.
  Added a new virtual method 'subst_argument_checker' to be used
  as an amnalyzer method.
  This method is supposed to set its in/out argument to NULL for
  the nodes where substitution of a string field for a constant
  is not valid.
sql/item_cmpfunc.cc:
  Fixed bug #21698.
  Added an implementation of the compile method for class Item_cond.
  First it processes the Item_cond node with a callback function and if
  the latter returns TRUE it proceeds with a transformation performed by
  another callback function.
sql/item_cmpfunc.h:
  Fixed bug #21698.
  Added the implementations of 'subst_argument_checker'
  for the Item_func and Item_cond classes.
  This method is supposed to set its in/out argument to NULL for
  the nodes where substitution of a string field for a constant
  is not valid.
  Added the declaration of an implementation of the compile method for 
  class Item_cond.
  First it processes the Item_cond node with a callback function and if
  the latter returns TRUE it proceeds with a transformation performed by
  another callback function.
sql/item_func.cc:
  Fixed bug #21698.
  Added an implementation of the compile method for class Item_func.
  First it processes the Item_func node with a callback function and if
  the latter returns TRUE it proceeds with a transformation performed by
  another callback function.
sql/item_func.h:
  Fixed bug #21698.
  Added the declaration of the implementation of the compile method for
  class Item_func.
  First it processes the Item_func node with a callback function and if
  the latter returns TRUE it proceeds with a transformation performed by
  another callback function.
sql/sql_select.cc:
  Fixed bug #21698.
  Limited the conditions at which a field can be substituted 
  a for an equal constant in a formula. 
  This substitution is allowed if the field is not of a type string
  or if the field reference serves as an argument of a comparison
  predicate.

1 files changed, 27 insertions, 0 deletions

diff --git a/mysql-test/t/func_str.test b/mysql-test/t/func_str.test
index 8753db0ebe1..415c6d2a44e 100644
--- a/mysql-test/t/func_str.test
+++ b/mysql-test/t/func_str.test
@@ -753,4 +753,31 @@ select cast(rtrim(ltrim('  20.06 ')) as decimal(19,2));
 select conv("18383815659218730760",10,10) + 0;
 select "18383815659218730760" + 0;
 
+#
+# Bug #21698: substitution of a string field for a constant under a function 
+#
+
+CREATE TABLE t1 (code varchar(10));
+INSERT INTO t1 VALUES ('a12'), ('A12'), ('a13');
+
+SELECT ASCII(code), code FROM t1 WHERE code='A12';
+SELECT ASCII(code), code FROM t1 WHERE code='A12' AND ASCII(code)=65;
+
+INSERT INTO t1 VALUES ('a12 '), ('A12  ');
+
+SELECT LENGTH(code), code FROM t1 WHERE code='A12';
+SELECT LENGTH(code), code FROM t1 WHERE code='A12' AND LENGTH(code)=5;
+
+ALTER TABLE t1 ADD INDEX (code);
+CREATE TABLE t2 (id varchar(10) PRIMARY KEY);
+INSERT INTO t2 VALUES ('a11'), ('a12'), ('a13'), ('a14');
+
+SELECT * FROM t1 INNER JOIN t2 ON t1.code=t2.id 
+  WHERE t2.id='a12' AND (code < 'a00' OR LENGTH(code)=5);
+EXPLAIN EXTENDED 
+SELECT * FROM t1 INNER JOIN t2 ON code=id 
+  WHERE id='a12' AND (code < 'a00' OR LENGTH(code)=5);
+
+DROP TABLE t1,t2;
+
 --echo End of 5.0 tests