MDEV-10421 duplicate CHECK CONSTRAINTs.

        mysql_prepare_create_table fixed so it doesn't let duplicating
        constraint names. Syntax for CONSTRAINT IF NOT EXISTS added
        and handled in mysql_alter_table.

5 files changed, 63 insertions, 4 deletions

diff --git a/sql/share/errmsg-utf8.txt b/sql/share/errmsg-utf8.txt
index 43de678e1c2..37012c17bfb 100644
--- a/sql/share/errmsg-utf8.txt
+++ b/sql/share/errmsg-utf8.txt
@@ -6762,8 +6762,8 @@ ER_FK_CANNOT_OPEN_PARENT
 ER_FK_INCORRECT_OPTION
         eng "Failed to add the foreign key constraint on table '%s'. Incorrect options in FOREIGN KEY constraint '%s'"
 
-ER_FK_DUP_NAME
-	eng "Duplicate foreign key constraint name '%s'"
+ER_DUP_CONSTRAINT_NAME
+       eng "Duplicate %s constraint name '%s'"
 
 ER_PASSWORD_FORMAT
   eng "The password hash doesn't have the expected format. Check if the correct password algorithm is being used with the PASSWORD() function."
diff --git a/sql/sql_alter.h b/sql/sql_alter.h
index 9e5fbaa425f..faba3a14a1b 100644
--- a/sql/sql_alter.h
+++ b/sql/sql_alter.h
@@ -174,6 +174,8 @@ public:
   List<Key>                     key_list;
   // List of columns, used by both CREATE and ALTER TABLE.
   List<Create_field>            create_list;
+
+  static const uint CHECK_CONSTRAINT_IF_NOT_EXISTS= 1;
   List<Virtual_column_info>     check_constraint_list;
   // Type of ALTER TABLE operation.
   uint                          flags;
diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index e03446010b6..af461d05036 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -3003,9 +3003,12 @@ public:
     return false;
   }
   // Add a constraint as a part of CREATE TABLE or ALTER TABLE
-  bool add_constraint(LEX_STRING *name, Virtual_column_info *constr)
+  bool add_constraint(LEX_STRING *name, Virtual_column_info *constr,
+                      bool if_not_exists)
   {
     constr->name= *name;
+    constr->flags= if_not_exists ?
+                   Alter_info::CHECK_CONSTRAINT_IF_NOT_EXISTS : 0;
     alter_info.check_constraint_list.push_back(constr);
     return false;
   }
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 7784a2b188a..80fadde714f 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -4201,6 +4201,22 @@ mysql_prepare_create_table(THD *thd, HA_CREATE_INFO *create_info,
         make_unique_constraint_name(thd, &check->name,
                                     &alter_info->check_constraint_list,
                                     &nr);
+      {
+        /* Check that there's no repeating constraint names. */
+        List_iterator_fast<Virtual_column_info>
+          dup_it(alter_info->check_constraint_list);
+        Virtual_column_info *dup_check;
+        while ((dup_check= dup_it++) && dup_check != check)
+        {
+          if (check->name.length == dup_check->name.length &&
+              my_strcasecmp(system_charset_info,
+                            check->name.str, dup_check->name.str) == 0)
+          {
+            my_error(ER_DUP_CONSTRAINT_NAME, MYF(0), "CHECK", check->name);
+            DBUG_RETURN(TRUE);
+          }
+        }
+      }
 
       if (check_string_char_length(&check->name, 0, NAME_CHAR_LEN,
                                    system_charset_info, 1))
@@ -6153,6 +6169,39 @@ remove_key:
   }
 #endif /*WITH_PARTITION_STORAGE_ENGINE*/
 
+  /* ADD CONSTRAINT IF NOT EXISTS. */
+  {
+    List_iterator<Virtual_column_info> it(alter_info->check_constraint_list);
+    Virtual_column_info *check;
+    TABLE_SHARE *share= table->s;
+    uint c;
+    while ((check=it++))
+    {
+      if ((!check->flags & Alter_info::CHECK_CONSTRAINT_IF_NOT_EXISTS) &&
+          check->name.length)
+        continue;
+      check->flags= 0;
+      for (c= share->field_check_constraints;
+           c < share->table_check_constraints ; c++)
+      {
+        Virtual_column_info *dup= table->check_constraints[c];
+        if (dup->name.length == check->name.length &&
+            my_strcasecmp(system_charset_info,
+                          check->name.str, dup->name.str) == 0)
+        {
+          push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
+            ER_DUP_CONSTRAINT_NAME, ER_THD(thd, ER_DUP_CONSTRAINT_NAME),
+            "CHECK", check->name.str);
+          it.remove();
+          if (alter_info->check_constraint_list.elements == 0)
+            alter_info->flags&= ~Alter_info::ALTER_ADD_CHECK_CONSTRAINT;
+
+          break;
+        }
+      }
+    }
+  }
+
   DBUG_VOID_RETURN;
 }
 
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 63ba77caa22..5908c7d3cb8 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -6073,7 +6073,7 @@ key_def:
 constraint_def:
          opt_constraint check_constraint
          {
-           Lex->add_constraint(&$1, $2);
+           Lex->add_constraint(&$1, $2, FALSE);
          }
        ;
 
@@ -7560,6 +7560,11 @@ alter_list_item:
           {
             Lex->alter_info.flags|= Alter_info::ALTER_ADD_CHECK_CONSTRAINT;
 	  }
+        | ADD CONSTRAINT IF_SYM not EXISTS field_ident check_constraint
+         {
+           Lex->alter_info.flags|= Alter_info::ALTER_ADD_CHECK_CONSTRAINT;
+           Lex->add_constraint(&$6, $7, TRUE);
+         }
         | CHANGE opt_column opt_if_exists_table_element field_ident
           field_spec opt_place
           {