oracle bitmap join index

下面是官网对于位图联合索引的说明

Use the bitmap_join_index_clause to define a bitmap join index. A bitmap join index is defined on a single table. For an index key made up of dimension table columns, it stores the fact table rowids corresponding to that key. In a data warehousing environment, the table on which the index is defined is commonly referred to as afact table, and the tables with which this table is joined are commonly referred to asdimension tables. However, a star schema is not a requirement for creating a join index.

ON In the ON clause, first specify the fact table, and then inside the parentheses specify the columns of the dimension tables on which the index is defined.

FROM In the FROM clause, specify the joined tables.

WHERE In the WHERE clause, specify the join condition.

If the underlying fact table is partitioned, you must also specify one of the local_partitioned_index clauses (see local_partitioned_index ).

Restrictions on Bitmap Join Indexes In addition to the restrictions on bitmap indexes in general (seeBITMAP), the following restrictions apply to bitmap join indexes:

• You cannot create a bitmap join index on an index-organized table or a temporary table.

• No table may appear twice in the FROM clause.

• You cannot create a function-based join index.

• The dimension table columns must be either primary key columns or have unique constraints.

• If a dimension table has a composite primary key, each column in the primary key must be part of the join.

• You cannot specify the local_index_clauses unless the fact table is partitioned.