ADD CONSTRAINT IF NOT EXISTS didn't work in SP

"if not exists" must be stored in a separate read-only property

mysql-test/main/constraints.result

@@ -183,7 +183,9 @@ t1	CREATE TABLE `t1` (
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 DROP PROCEDURE sp;
 DROP TABLE t1;
+#
 # End of 10.2 tests
+#
 create table t1 (a int check (a>10)) select 100 as 'a';
 show create table t1;
 Table	Create Table
@@ -201,3 +203,35 @@ a
 19
 ccc
 drop table t1;
+create table t1 (a int, b int);
+create procedure sp() alter table t1 add constraint if not exists foo check (b > 0);
+call sp;
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  `b` int(11) DEFAULT NULL,
+  CONSTRAINT `foo` CHECK (`b` > 0)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+call sp;
+Warnings:
+Note	1826	Duplicate CHECK constraint name 'foo'
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  `b` int(11) DEFAULT NULL,
+  CONSTRAINT `foo` CHECK (`b` > 0)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+call sp;
+Warnings:
+Note	1826	Duplicate CHECK constraint name 'foo'
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  `b` int(11) DEFAULT NULL,
+  CONSTRAINT `foo` CHECK (`b` > 0)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
+drop procedure sp;
+drop table t1;

mysql-test/main/constraints.test

@@ -151,7 +151,9 @@ show create table t1;
 DROP PROCEDURE sp;
 DROP TABLE t1;
 
+--echo #
 --echo # End of 10.2 tests
+--echo #
 
 #
 # Check that we don't lose constraints as part of CREATE ... SELECT
@@ -172,3 +174,18 @@ insert into t1 values ("ccc");
 insert into t1 values ("");
 select * from t1;
 drop table t1;
+
+#
+# add if not exists in SP
+#
+
+create table t1 (a int, b int);
+create procedure sp() alter table t1 add constraint if not exists foo check (b > 0);
+call sp;
+show create table t1;
+call sp;
+show create table t1;
+call sp;
+show create table t1;
+drop procedure sp;
+drop table t1;

sql/field.h

@@ -558,7 +558,6 @@ static inline const char *vcol_type_name(enum_vcol_info_type type)
 #define VCOL_AUTO_INC         16
 #define VCOL_IMPOSSIBLE       32
 #define VCOL_NEXTVAL          64  /* NEXTVAL is not implemented for vcols */
-#define VCOL_CHECK_CONSTRAINT_IF_NOT_EXISTS 128
 
 #define VCOL_NOT_STRICTLY_DETERMINISTIC                       \
   (VCOL_NON_DETERMINISTIC | VCOL_TIME_FUNC | VCOL_SESSION_FUNC)
@@ -590,6 +589,7 @@ public:
   bool stored_in_db;
   bool utf8;                                    /* Already in utf8 */
   bool automatic_name;
+  bool if_not_exists;
   Item *expr;
   Lex_ident name;                               /* Name of constraint */
   /* see VCOL_* (VCOL_FIELD_REF, ...) */

sql/sql_lex.h

@@ -4375,7 +4375,7 @@ public:
                       bool if_not_exists)
   {
     constr->name= name;
-    constr->flags= if_not_exists ? VCOL_CHECK_CONSTRAINT_IF_NOT_EXISTS : 0;
+    constr->if_not_exists= if_not_exists;
     alter_info.check_constraint_list.push_back(constr);
     return false;
   }

sql/sql_table.cc

@@ -6928,10 +6928,8 @@ remove_key:
 
     while ((check=it++))
     {
-      if (!(check->flags & VCOL_CHECK_CONSTRAINT_IF_NOT_EXISTS) &&
+      if (!check->if_not_exists && check->name.length)
-          check->name.length)
         continue;
-      check->flags= 0;
       for (c= share->field_check_constraints;
            c < share->table_check_constraints ; c++)
       {