MDEV-31607 ER_DUP_KEY in mysql.innodb_table_stats upon RENAME on sequence

ha_innobase::delete_table(): Also on DROP SEQUENCE, do try to drop any
persistent statistics. They should really not be created for
SEQUENCE objects (which internally are 1-row no-rollback tables),
but that is how happened to always work.

mysql-test/suite/sql_sequence/alter.result

@@ -248,3 +248,17 @@ SELECT NEXTVAL(s);
 NEXTVAL(s)
 1
 DROP SEQUENCE s;
+#
+# MDEV-31607 ER_DUP_KEY in mysql.table_stats upon REANME on sequence
+#
+CREATE SEQUENCE s1 ENGINE=InnoDB;
+CREATE SEQUENCE s2 ENGINE=InnoDB;
+SHOW CREATE SEQUENCE s1;
+Table	Create Table
+s1	CREATE SEQUENCE `s1` start with 1 minvalue 1 maxvalue 9223372036854775806 increment by 1 cache 1000 nocycle ENGINE=InnoDB
+SHOW CREATE SEQUENCE s2;
+Table	Create Table
+s2	CREATE SEQUENCE `s2` start with 1 minvalue 1 maxvalue 9223372036854775806 increment by 1 cache 1000 nocycle ENGINE=InnoDB
+DROP SEQUENCE s2;
+RENAME TABLE s1 TO s2;
+DROP SEQUENCE s2;

mysql-test/suite/sql_sequence/alter.test

@@ -161,3 +161,15 @@ CREATE SEQUENCE s;
 ALTER TABLE s ORDER BY cache_size;
 SELECT NEXTVAL(s);
 DROP SEQUENCE s;
+
+--echo #
+--echo # MDEV-31607 ER_DUP_KEY in mysql.table_stats upon REANME on sequence
+--echo #
+
+CREATE SEQUENCE s1 ENGINE=InnoDB;
+CREATE SEQUENCE s2 ENGINE=InnoDB;
+SHOW CREATE SEQUENCE s1;
+SHOW CREATE SEQUENCE s2;
+DROP SEQUENCE s2;
+RENAME TABLE s1 TO s2;
+DROP SEQUENCE s2;

storage/innobase/handler/ha_innodb.cc

@@ -13748,13 +13748,12 @@ int ha_innobase::delete_table(const char *name)
   }
 
   if (!table->no_rollback())
-  {
     err= trx->drop_table_foreign(table->name);
-    if (err == DB_SUCCESS && table_stats && index_stats)
-      err= trx->drop_table_statistics(table->name);
-    if (err != DB_SUCCESS)
-      goto err_exit;
-  }
+
+  if (err == DB_SUCCESS && table_stats && index_stats)
+    err= trx->drop_table_statistics(table->name);
+  if (err != DB_SUCCESS)
+    goto err_exit;
 
   err= trx->drop_table(*table);
   if (err != DB_SUCCESS)