Oracle SQL Statement alter index and add partition

You can't use interval partitioning with reference partitioning, however, It's possible to mix range partitioning and reference partitioning, as shown in the example of reference partitioning in the 11g doc:

The benefit of this extension is that tables with a parent-child relationship can be logically equipartitioned by inheriting the partitioning key from the parent table without duplicating the key columns. The logical dependency also automatically cascades partition maintenance operations, thus making application development easier and less error-prone.

The child table doesn't need to contain the partition key (here the log date). It inherits the partition key from the parent table.

Range partitioning involves a bit more maintenance because you have to create the partitions yourself. However, once the partitions are created, range and interval work similarly.

My opinion is that partitioning of that table in the manner presented may be useful.

Your queries will be two times faster (in the case when partitions are almost equal) if they make full scans.

In case your queryes have another tone of filters/conditions and use indexes, partitioning is not useful, because the level of an index is almost not affected by doubling the number of values.

UPDATE: For the test you did (SELECT * FROM table1 WHERE TENANTID=2) it is sure that partitioning is best. The bitmap solution need to scan the index, and after this, to scan all table's blocks containing rows with tenantid=2(it knows what are the rows). But partitioning will cause just scanning the table's partition with tenantid=2. They are phisically separated to tenantid=1.

So, two scans(index scan + table scan) vs one table scan(wich may be smaller).