MDEV-17503 CREATE SEQUENCE failed with innodb_force_primary_key =1

Fixed by adding table flag HA_WANTS_PRIMARY_KEY, which is like
HA_REQUIRE_PRIMARY_KEY but tells SQL upper layer that the storage engine
internally can handle tables without primary keys (for example for
sequences or trough user variables)

mysql-test/suite/sql_sequence/create.result

@@ -644,3 +644,12 @@ TABLE_ID	NAME	FLAG	N_COLS	SPACE	ROW_FORMAT	ZIP_PAGE_SIZE	SPACE_TYPE
 DROP SEQUENCE seq1;
 CREATE TEMPORARY SEQUENCE seq1 ENGINE=InnoDB ROW_FORMAT=REDUNDANT;
 DROP TEMPORARY SEQUENCE seq1;
+#
+# MDEV-17503 CREATE SEQUENCE failed with innodb_force_primary_key =1
+#
+set global innodb_force_primary_key =1;
+CREATE SEQUENCE s1 START WITH 100 INCREMENT BY 10 ENGINE=innodb;
+set global innodb_force_primary_key=default;
+ALTER TABLE s1 ADD PRIMARY KEY (next_not_cached_value);
+ERROR HY000: Sequence 'test.s1' table structure is invalid (Sequence tables cannot have any keys)
+DROP SEQUENCE s1;

mysql-test/suite/sql_sequence/create.test

@@ -462,3 +462,14 @@ SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_TABLES WHERE NAME='test/seq1';
 DROP SEQUENCE seq1;
 CREATE TEMPORARY SEQUENCE seq1 ENGINE=InnoDB ROW_FORMAT=REDUNDANT;
 DROP TEMPORARY SEQUENCE seq1;
+
+--echo #
+--echo # MDEV-17503 CREATE SEQUENCE failed with innodb_force_primary_key =1
+--echo #
+
+set global innodb_force_primary_key =1;
+CREATE SEQUENCE s1 START WITH 100 INCREMENT BY 10 ENGINE=innodb;
+set global innodb_force_primary_key=default;
+--error ER_SEQUENCE_INVALID_TABLE_STRUCTURE
+ALTER TABLE s1 ADD PRIMARY KEY (next_not_cached_value);
+DROP SEQUENCE s1;

sql/ha_partition.h

@@ -1041,6 +1041,10 @@ class ha_partition :public handler
     with hidden primary key)
     (No handler has this limitation currently)
 
+    HA_WANTS_PRIMARY_KEY:
+    Can't define a table without primary key except sequences
+    (Only InnoDB has this when using innodb_force_primary_key == ON)
+
     HA_STATS_RECORDS_IS_EXACT:
     Does the counter of records after the info call specify an exact
     value or not. If it does this flag is set.

sql/handler.h

@@ -301,6 +301,9 @@ enum enum_alter_inplace_result {
 /* calling cmp_ref() on the engine is expensive */
 #define HA_CMP_REF_IS_EXPENSIVE (1ULL << 54)
 
+/* Engine wants primary keys for everything except sequences */
+#define HA_WANTS_PRIMARY_KEY (1ULL << 55)
+
 /* bits in index_flags(index_number) for what you can do with index */
 #define HA_READ_NEXT            1       /* TODO really use this flag */
 #define HA_READ_PREV            2       /* supports ::index_prev */

sql/sql_table.cc

@@ -4134,7 +4134,9 @@ mysql_prepare_create_table(THD *thd, HA_CREATE_INFO *create_info,
   }
 
   if (!unique_key && !primary_key &&
-      (file->ha_table_flags() & HA_REQUIRE_PRIMARY_KEY))
+      ((file->ha_table_flags() & HA_REQUIRE_PRIMARY_KEY) ||
+       ((file->ha_table_flags() & HA_WANTS_PRIMARY_KEY) &&
+        !create_info->sequence)))
   {
     my_message(ER_REQUIRES_PRIMARY_KEY, ER_THD(thd, ER_REQUIRES_PRIMARY_KEY),
                MYF(0));

storage/innobase/handler/ha_innodb.cc

@@ -2918,7 +2918,7 @@ ha_innobase::ha_innobase(
 			  | HA_CAN_RTREEKEYS
                           | HA_CAN_TABLES_WITHOUT_ROLLBACK
 			  | HA_CONCURRENT_OPTIMIZE
-			  |  (srv_force_primary_key ? HA_REQUIRE_PRIMARY_KEY : 0)
+			  |  (srv_force_primary_key ? HA_WANTS_PRIMARY_KEY : 0)
 		  ),
 	m_start_of_scan(),
         m_mysql_has_locked()