MDEV-480: TRUNCATE TABLE on a Cassandra table does not remove rows

- Remove HTON_CAN_RECREATE flag, re-create won't delete rows in cassandra.

mysql-test/r/cassandra.result

@@ -156,3 +156,13 @@ Cassandra_multiget_keys_scanned	16
 Cassandra_multiget_rows_read	16
 delete from t1;
 drop table t1;
+#
+# MDEV-480: TRUNCATE TABLE on a Cassandra table does not remove rows
+#
+CREATE TABLE t1 (rowkey BIGINT PRIMARY KEY, a BIGINT) ENGINE=CASSANDRA
+thrift_host='localhost' keyspace='mariadbtest2' column_family = 'cf2';
+INSERT INTO t1 VALUES (0,0),(1,1),(2,2);
+truncate table t1;
+select * from t1;
+rowkey	a
+drop table t1;

mysql-test/t/cassandra.test

@@ -159,9 +159,19 @@ insert into t1 values(7, 8);
 select * from t1 A, t1 B where B.rowkey=A.a;
 show status like 'cassandra_multi%';
 
-
 delete from t1;
 drop table t1;
+
+--echo #
+--echo # MDEV-480: TRUNCATE TABLE on a Cassandra table does not remove rows
+--echo #
+CREATE TABLE t1 (rowkey BIGINT PRIMARY KEY, a BIGINT) ENGINE=CASSANDRA
+  thrift_host='localhost' keyspace='mariadbtest2' column_family = 'cf2';
+INSERT INTO t1 VALUES (0,0),(1,1),(2,2);
+truncate table t1;
+select * from t1;
+drop table t1;
+ 
 ############################################################################
 ## Cassandra cleanup
 ############################################################################

storage/cassandra/ha_cassandra.cc

@@ -142,7 +142,12 @@ static int cassandra_init_func(void *p)
 
   cassandra_hton->state=   SHOW_OPTION_YES;
   cassandra_hton->create=  cassandra_create_handler;
-  cassandra_hton->flags=   HTON_CAN_RECREATE;
+  /* 
+    Don't specify HTON_CAN_RECREATE in flags. re-create is used by TRUNCATE
+    TABLE to create an *empty* table from scratch. Cassandra table won't be
+    emptied if re-created.
+  */
+  cassandra_hton->flags=   0; 
   cassandra_hton->table_options= cassandra_table_option_list;
   //cassandra_hton->field_options= example_field_option_list;
   cassandra_hton->field_options= NULL;