Setting a variable to CAST(NULL as X) set the result type of the variable to X. (Bug #6598)

mysql-test/r/bigint.result:
  Test to show show that the parser threats big longlong values as unsigned
mysql-test/r/user_var.result:
  Test of CAST(NULL as SIGNED/UNSIGNED)
mysql-test/t/bigint.test:
  Test to show show that the parser threats big longlong values as unsigned
mysql-test/t/user_var.test:
  Test of CAST(NULL as SIGNED/UNSIGNED)
sql/item_func.cc:
  Setting a variable to CAST(NULL as X) set the result type of the variable to X. (Bug #6598)
  Setting a variable to NULL doesn't change the old result type.
sql/item_func.h:
  Detect setting a variable to NULL
sql/unireg.cc:
  Safety fix

1 files changed, 41 insertions, 0 deletions

diff --git a/mysql-test/r/user_var.result b/mysql-test/r/user_var.result
index 68eae111111..d9a647ce2c3 100644
--- a/mysql-test/r/user_var.result
+++ b/mysql-test/r/user_var.result
@@ -182,3 +182,44 @@ coercibility(@v1)	coercibility(@v2)	coercibility(@v3)	coercibility(@v4)
 set session @honk=99;
 set one_shot @honk=99;
 ERROR HY000: The 'SET ONE_SHOT' syntax is reserved for purposes internal to the MySQL server
+set @first_var= NULL;
+create table t1 select @first_var;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `@first_var` longblob
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;
+set @first_var= cast(NULL as signed integer);
+create table t1 select @first_var;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `@first_var` bigint(20) default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;
+set @first_var= NULL;
+create table t1 select @first_var;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `@first_var` bigint(20) default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;
+set @first_var= concat(NULL);
+create table t1 select @first_var;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `@first_var` longblob
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;
+set @first_var=1;
+set @first_var= cast(NULL as CHAR);
+create table t1 select @first_var;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `@first_var` longtext
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;