Make ha_cassandra work with filesort().

mysql-test/r/cassandra.result

@@ -45,4 +45,17 @@ rowkey11	NULL	NULL
 delete from t1;
 select * from t1;
 rowkey	data1	data2
+#
+# A query with filesort (check that table_flags() & HA_REC_NOT_IN_SEQ,
+#  also check ::rnd_pos()
+#
+insert into t1 values ('rowkey10', 'data1-value', 123456);
+insert into t1 values ('rowkey11', 'data1-value2', 34543);
+insert into t1 values ('rowkey12', 'data1-value3', 454);
+select * from t1 order by data2;
+rowkey	data1	data2
+rowkey12	data1-value3	454
+rowkey11	data1-value2	34543
+rowkey10	data1-value	123456
+delete from t1;
 drop table t1;

mysql-test/t/cassandra.test

@@ -84,6 +84,16 @@ select * from t1;
 delete from t1;
 select * from t1;
 
+--echo #
+--echo # A query with filesort (check that table_flags() & HA_REC_NOT_IN_SEQ,
+--echo #  also check ::rnd_pos()
+--echo #
+insert into t1 values ('rowkey10', 'data1-value', 123456);
+insert into t1 values ('rowkey11', 'data1-value2', 34543);
+insert into t1 values ('rowkey12', 'data1-value3', 454);
+select * from t1 order by data2;
+
+delete from t1;
 drop table t1;
 
 ############################################################################

storage/cassandra/ha_cassandra.cc

@@ -755,7 +755,10 @@ int ha_cassandra::rnd_init(bool scan)
   bool bres;
   DBUG_ENTER("ha_cassandra::rnd_init");
   if (!scan)
-    DBUG_RETURN(HA_ERR_WRONG_COMMAND);
+  {
+    /* Prepare for rnd_pos() calls. We don't need to anything. */
+    DBUG_RETURN(0);
+  }
 
   se->clear_read_columns();
   for (uint i= 1; i < table->s->fields; i++)

storage/cassandra/ha_cassandra.h

@@ -78,11 +78,17 @@ public:
   ulonglong table_flags() const
   {
     /*
+      HA_BINLOG_STMT_CAPABLE
         We are saying that this engine is just statement capable to have
         an engine that can only handle statement-based logging. This is
         used in testing.
+      HA_REC_NOT_IN_SEQ 
+        If we don't set it, filesort crashes, because it assumes rowids are 
+        1..8 byte numbers 
     */
-    return HA_BINLOG_STMT_CAPABLE;
+    return HA_BINLOG_STMT_CAPABLE | 
+           HA_REC_NOT_IN_SEQ; 
+
   }
 
   /** @brief