Bug#26277 User variable returns one type in SELECT @v and other for CREATE as SELECT @v

- Adding variable m_cached_result_type to keep the variable type consistent
  during the execution of a statement.
- Before each result set is returned to the client the description of each
  column is sent as meta data.
  Previously the result type for a column could change if the hash variable
  entry changed between statements. This caused the result set of the query
  to alternate column types in certain cases which is not supported by MySQL
  client-server protocol. Example:
  Previously this sequence:
    SET @A:=1;
    SELECT @A:="text", @A;
  would return "text", "text";
 
  After the change the SELECT returns "text", 0
  The reson for this is that previously the result set from 'SELECT @A;'
  would always be of the type STRING, whereas now the type of the variable
  is taken from the last SET statement. However, 'SELECT @A:="text"' will
  return type of STRING since the right side of the assignment is used.

mysql-test/r/sp-vars.result

@@ -1161,3 +1161,29 @@ CALL p1();
 v_text
 abc|def
 DROP PROCEDURE p1;
+drop function if exists f1;
+drop table if exists t1;
+create function f1() returns int 
+begin
+if @a=1 then set @b='abc';
+else set @b=1;
+end if;
+set @a=1;
+return 0;
+end|
+create table t1 (a int)|
+insert into t1 (a) values (1), (2)|
+set @b=1|
+set @a=0|
+select f1(), @b from t1|
+f1()	@b
+0	1
+0	0
+set @b:='test'|
+set @a=0|
+select f1(), @b from t1|
+f1()	@b
+0	1
+0	abc
+drop function f1;
+drop table t1;

mysql-test/r/type_date.result

@@ -110,15 +110,24 @@ select 1 from t1 where cast('2000-01-01 12:01:01' as datetime) between start_dat
 1
 1
 drop table t1;
-select @d:=1111, year(@d), month(@d), day(@d), cast(@d as date);
-@d:=1111	year(@d)	month(@d)	day(@d)	cast(@d as date)
-1111	2000	11	11	2000-11-11
-select @d:=011111, year(@d), month(@d), day(@d), cast(@d as date);
-@d:=011111	year(@d)	month(@d)	day(@d)	cast(@d as date)
-11111	2001	11	11	2001-11-11
-select @d:=1311, year(@d), month(@d), day(@d), cast(@d as date);
-@d:=1311	year(@d)	month(@d)	day(@d)	cast(@d as date)
-1311	NULL	NULL	NULL	NULL
+select @d:=1111;
+@d:=1111
+1111
+select year(@d), month(@d), day(@d), cast(@d as date);
+year(@d)	month(@d)	day(@d)	cast(@d as date)
+2000	11	11	2000-11-11
+select @d:=011111;
+@d:=011111
+11111
+select year(@d), month(@d), day(@d), cast(@d as date);
+year(@d)	month(@d)	day(@d)	cast(@d as date)
+2001	11	11	2001-11-11
+select @d:=1311;
+@d:=1311
+1311
+select year(@d), month(@d), day(@d), cast(@d as date);
+year(@d)	month(@d)	day(@d)	cast(@d as date)
+NULL	NULL	NULL	NULL
 Warnings:
 Warning	1292	Incorrect datetime value: '1311'
 Warning	1292	Incorrect datetime value: '1311'

mysql-test/r/user_var.result

@@ -91,7 +91,7 @@ NULL	test	test
 set @g=1;
 select @g,(@g:=c),@g from t1;
 @g	(@g:=c)	@g
-1	test	test
+1	test	0
 select @c, @d, @e, @f;
 @c	@d	@e	@f
 1	1	2	test

mysql-test/t/sp-vars.test

@@ -1368,3 +1368,39 @@ CALL p1();
 DROP PROCEDURE p1;
 
 # End of 5.0 tests.
+
+#
+# Bug #26277 User variable returns one type in SELECT @v and other for CREATE as SELECT @v
+#
+--disable_warnings
+drop function if exists f1;
+drop table if exists t1;
+--enable_warnings
+
+delimiter |;
+create function f1() returns int 
+begin
+ if @a=1 then set @b='abc';
+ else set @b=1;
+ end if;
+ set @a=1;
+ return 0;
+end|
+
+create table t1 (a int)|
+insert into t1 (a) values (1), (2)|
+
+set @b=1|
+set @a=0|
+select f1(), @b from t1|
+
+set @b:='test'|
+set @a=0|
+select f1(), @b from t1|
+
+delimiter ;|
+
+drop function f1;
+drop table t1;
+# End of 5.1 tests.
+

mysql-test/t/type_date.test

@@ -128,9 +128,12 @@ drop table t1;
 # Bug #23093: Implicit conversion of 9912101 to date does not match
 # cast(9912101 as date)
 #
-select @d:=1111, year(@d), month(@d), day(@d), cast(@d as date);
-select @d:=011111, year(@d), month(@d), day(@d), cast(@d as date);
-select @d:=1311, year(@d), month(@d), day(@d), cast(@d as date);
+select @d:=1111;
+select year(@d), month(@d), day(@d), cast(@d as date);
+select @d:=011111;
+select year(@d), month(@d), day(@d), cast(@d as date);
+select @d:=1311;
+select year(@d), month(@d), day(@d), cast(@d as date);
 create table t1 (d  date , dt datetime , ts timestamp);
 insert into t1 values (9912101,9912101,9912101);
 insert into t1 values (11111,11111,11111);

sql/item_func.cc

@@ -36,7 +36,6 @@
 #define sp_restore_security_context(A,B) while (0) {}
 #endif
 
-
 bool check_reserved_words(LEX_STRING *name)
 {
   if (!my_strcasecmp(system_charset_info, name->str, "GLOBAL") ||
@@ -4380,7 +4379,6 @@ int get_var_with_binlog(THD *thd, enum_sql_command sql_command,
   return 1;
 }
 
-
 void Item_func_get_user_var::fix_length_and_dec()
 {
   THD *thd=current_thd;
@@ -4391,10 +4389,19 @@ void Item_func_get_user_var::fix_length_and_dec()
 
   error= get_var_with_binlog(thd, thd->lex->sql_command, name, &var_entry);
 
+  /*
+    If the variable didn't exist it has been created as a STRING-type.
+    'var_entry' is NULL only if there occured an error during the call to
+    get_var_with_binlog.
+  */
   if (var_entry)
   {
+    m_cached_result_type= var_entry->type;
+    unsigned_flag= var_entry->unsigned_flag;
+    max_length= var_entry->length;
+
     collation.set(var_entry->collation);
-    switch (var_entry->type) {
+    switch(m_cached_result_type) {
     case REAL_RESULT:
       max_length= DBL_DIG + 8;
       break;
@@ -4419,6 +4426,8 @@ void Item_func_get_user_var::fix_length_and_dec()
   {
     collation.set(&my_charset_bin, DERIVATION_IMPLICIT);
     null_value= 1;
+    m_cached_result_type= STRING_RESULT;
+    max_length= MAX_BLOB_WIDTH;
   }
 
   if (error)
@@ -4436,12 +4445,7 @@ bool Item_func_get_user_var::const_item() const
 
 enum Item_result Item_func_get_user_var::result_type() const
 {
-  user_var_entry *entry;
-  if (!(entry = (user_var_entry*) hash_search(&current_thd->user_vars,
-					      (byte*) name.str,
-					      name.length)))
-    return STRING_RESULT;
-  return entry->type;
+  return m_cached_result_type;
 }
 
 

sql/item_func.h

@@ -1247,11 +1247,12 @@ class Item_func_get_user_var :public Item_func,
                               private Settable_routine_parameter
 {
   user_var_entry *var_entry;
+  Item_result m_cached_result_type;
 
 public:
   LEX_STRING name; // keep it public
   Item_func_get_user_var(LEX_STRING a):
-    Item_func(), name(a) {}
+    Item_func(), name(a), m_cached_result_type(STRING_RESULT) {}
   enum Functype functype() const { return GUSERVAR_FUNC; }
   LEX_STRING get_name() { return name; }
   double val_real();
@@ -1265,13 +1266,11 @@ class Item_func_get_user_var :public Item_func,
     We must always return variables as strings to guard against selects of type
     select @t1:=1,@t1,@t:="hello",@t from foo where (@t1:= t2.b)
   */
-  enum_field_types field_type() const  { return MYSQL_TYPE_VARCHAR; }
   const char *func_name() const { return "get_user_var"; }
   bool const_item() const;
   table_map used_tables() const
   { return const_item() ? 0 : RAND_TABLE_BIT; }
   bool eq(const Item *item, bool binary_cmp) const;
-
 private:
   bool set_value(THD *thd, sp_rcontext *ctx, Item **it);