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

4 files changed, 94 insertions, 0 deletions

diff --git a/mysql-test/r/bigint.result b/mysql-test/r/bigint.result
index e372c307ba7..a0c8f317db2 100644
--- a/mysql-test/r/bigint.result
+++ b/mysql-test/r/bigint.result
@@ -128,3 +128,20 @@ t2.value64=t1.value64;
 value64	value32	value64	value32
 9223372036854775807	2	9223372036854775807	4
 drop table t1, t2;
+create table t1 select 1 as 'a';
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` bigint(1) NOT NULL default '0'
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+drop table t1;
+create table t1 select 9223372036854775809 as 'a';
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` bigint(19) unsigned NOT NULL default '0'
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+select * from t1;
+a
+9223372036854775809
+drop table t1;
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;
diff --git a/mysql-test/t/bigint.test b/mysql-test/t/bigint.test
index a26b78254e7..99c8a13d0b5 100644
--- a/mysql-test/t/bigint.test
+++ b/mysql-test/t/bigint.test
@@ -104,3 +104,13 @@ t2.value64=t1.value64;
 
 drop table t1, t2;
 
+#
+# Test of CREATE ... SELECT and unsigned integers
+#
+create table t1 select 1 as 'a';
+show create table t1;
+drop table t1;
+create table t1 select 9223372036854775809 as 'a';
+show create table t1;
+select * from t1;
+drop table t1;
diff --git a/mysql-test/t/user_var.test b/mysql-test/t/user_var.test
index ef360f2231d..b9d06558f34 100644
--- a/mysql-test/t/user_var.test
+++ b/mysql-test/t/user_var.test
@@ -119,3 +119,29 @@ select coercibility(@v1),coercibility(@v2),coercibility(@v3),coercibility(@v4);
 set session @honk=99;
 --error 1382
 set one_shot @honk=99;
+
+#
+# Bug #6598: problem with cast(NULL as signed integer);
+#
+
+set @first_var= NULL;
+create table t1 select @first_var;
+show create table t1;
+drop table t1;
+set @first_var= cast(NULL as signed integer);
+create table t1 select @first_var;
+show create table t1;
+drop table t1;
+set @first_var= NULL;
+create table t1 select @first_var;
+show create table t1;
+drop table t1;
+set @first_var= concat(NULL);
+create table t1 select @first_var;
+show create table t1;
+drop table t1;
+set @first_var=1;
+set @first_var= cast(NULL as CHAR);
+create table t1 select @first_var;
+show create table t1;
+drop table t1;