bk commit into 4.1 tree (bar:1.2120) BUG#8785

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ChangeSet
  1.2120 05/03/15 17:15:47 bar@stripped +5 -0
  # Bug#8785 Problem with nested concats and
  character set conversion of a string constant.

  sql/sql_string.h
    1.55 05/03/15 17:15:43 bar@stripped +4 -0
    A new method to cut Alloced_length to str_length for
    string constants, to avoid reusing them as a buffer
    in things like CONCAT().

  sql/item_strfunc.cc
    1.220 05/03/15 17:15:43 bar@stripped +1 -2
    Remove previous fix: it was not 100% correct.
    A non const_item() can return a constant String.

  sql/item.cc
    1.194 05/03/15 17:15:43 bar@stripped +12 -0
    # Bug#8785 Problem with nested concats and
    character set conversion of a string constant.

  mysql-test/t/ctype_utf8.test
    1.50 05/03/15 17:15:43 bar@stripped +9 -0
    Addign test

  mysql-test/r/ctype_utf8.result
    1.50 05/03/15 17:15:43 bar@stripped +7 -0
    Adding test

# 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:	bar
# Host:	bar.intranet.mysql.r18.ru
# Root:	/usr/home/bar/mysql-4.1

--- 1.193/sql/item.cc	2005-03-09 18:50:57 +04:00
+++ 1.194/sql/item.cc	2005-03-15 17:15:43 +04:00
@@ -236,6 +236,18 @@
     return NULL;
   }
   conv->str_value.copy();
+  /* 
+    The above line executes str_value.realloc() internally,
+    which alligns Alloced_length using ALLIGN_SIZE.
+    In the case of Item_string::str_value we don't want
+    Alloced_length to be longer than str_length.
+    Otherwise, some functions like Item_func_concat::val_str()
+    try to reuse str_value as a buffer for concatenation result
+    for optimization purposes, so our string constant become
+    corrupted. See bug#8785 for more details.
+    Let's shrink Alloced_length to str_length to avoid this problem.
+  */
+  conv->str_value.shrink_to_length();
   return conv;
 }
 

--- 1.219/sql/item_strfunc.cc	2005-03-09 22:37:24 +04:00
+++ 1.220/sql/item_strfunc.cc	2005-03-15 17:15:43 +04:00
@@ -277,8 +277,7 @@
 			    current_thd->variables.max_allowed_packet);
 	goto null;
       }
-      if (!args[0]->const_item() && 
-          res->alloced_length() >= res->length()+res2->length())
+      if (res->alloced_length() >= res->length()+res2->length())
       {						// Use old buffer
 	res->append(*res2);
       }

--- 1.54/sql/sql_string.h	2005-02-15 04:55:37 +04:00
+++ 1.55/sql/sql_string.h	2005-03-15 17:15:43 +04:00
@@ -177,6 +177,10 @@
       }
     }
   }
+  inline void shrink_to_length()
+  {
+    Alloced_length= str_length;
+  }
   bool is_alloced() { return alloced; }
   inline String& operator = (const String &s)
   {

--- 1.49/mysql-test/r/ctype_utf8.result	2005-02-21 17:17:13 +04:00
+++ 1.50/mysql-test/r/ctype_utf8.result	2005-03-15 17:15:43 +04:00
@@ -861,6 +861,13 @@
 one	<one>
 two	<two>
 DROP TABLE t1;
+create table t1 (f1 varchar(1) not null) default charset utf8;
+insert into t1 values (''), ('');
+select concat(concat(_latin1'->',f1),_latin1'<-') from t1;
+concat(concat(_latin1'->',f1),_latin1'<-')
+-><-
+-><-
+drop table t1;
 select convert(_koi8r'É' using utf8) < convert(_koi8r'Ê' using utf8);
 convert(_koi8r'É' using utf8) < convert(_koi8r'Ê' using utf8)
 1

--- 1.49/mysql-test/t/ctype_utf8.test	2005-02-21 17:17:10 +04:00
+++ 1.50/mysql-test/t/ctype_utf8.test	2005-03-15 17:15:43 +04:00
@@ -695,6 +695,15 @@
 DROP TABLE t1;
 
 #
+# Bug#8785
+# the same problem with the above, but with nested CONCATs
+#
+create table t1 (f1 varchar(1) not null) default charset utf8;
+insert into t1 values (''), ('');
+select concat(concat(_latin1'->',f1),_latin1'<-') from t1;
+drop table t1;
+
+#
 # Bug#8385: utf8_general_ci treats Cyrillic letters I and SHORT I as the same
 #
 select convert(_koi8r'É' using utf8) < convert(_koi8r'Ê' using utf8);