Databases Reference
In-Depth Information
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| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
|
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| 0 | SELECT STATEMENT | | 1 | 2 | 975 (0)| 00:00:12 |
| 1 | SORT AGGREGATE | | 1 | 2 | | |
| 2 | BITMAP CONVERSION COUNT | | 21M| 40M| 975 (0)| 00:00:12 |
|* 3 | BITMAP INDEX SINGLE VALUE| EMPLOYEES_B2 | | | | |
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Predicate Information (identified by operation id):
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3 - access("GENDER"='F')
Statistics
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0 recursive calls
0 db block gets
996 consistent gets
996 physical reads
0 redo size
529 bytes sent via SQL*Net to client
523 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
With the star schema, bitmap indexes are essential to obtain successful query performance, and
bitmap indexes are, at a minimum, needed on all foreign key columns in the fact table. In addition, you
should have your database configured for star transformation. See Table 3-3 for the Oracle initialization
parameters that should be configured or analyzed for the proper value.
Table 3-3. Initialization Parameters for Star Transformation
Parameter Name
Value
star_transformation
TRUE (FALSE is the default)
memory_target
Variable. This parameter is used to configure both System Global Area (SGA)
and Program Global Area (PGA). Star transformation needs PGA memory
configured.
pga_aggregate_target
Configure this parameter if operating in versions 9i or 10g of Oracle
Database.
