Optimizing access to a database by utilizing a star join

1. A computer-implemented method for use in optimizing a database query for a star database schema including at least one fact table and at least one dimension table, in which the database query includes an IN-List condition, where the method includes:

Transforming, by a computer, the IN-List condition into a relation;

Joining, by said computer, the relation with the dimension table to produce a join result; and

joining, by said computer, the join result to the fact table.

2. The method of claim 1 further including:

determining, by said computer whether an IN-List exists within a WHERE clause.

3. The method of claim 1 further including:

determining, by said computer, whether an IN-List exists within an ON clause.

4. The method of claim 1 , further including:

evaluating, by said computer, for each of multiple different join paths, a cost associated with joining the relation with the dimension table, and selecting, by said computer, a lowest cost path from the different join paths.

5. The method of claim 1 further including:

evaluating, by said computer, for each of multiple different join paths, a cost associated with joining the join result with the fact table, and selecting, by said computer, a lowest cost path from the different join paths.

6. The method of claim 1 further including:

evaluating, by said computer, for each of multiple different join paths that include plans that use IN-List as a single table condition and plans that use IN-List as dimension table, a cost associated with the join path, and selecting, by said computer, a lowest cost path from the different join paths.

7. The method of claim 1 further including:

applying, by said computer, an index when joining the join result of to the fact table.

8. The method of claim 7 , where the index is a primary index of the fact table.

9. The method of claim 7 , where the index is a secondary index of the fact table.

10. The method of claim 7 , where the index is a primary index of a join index that at least partially covers the fact table.

11. The method of claim 7 , where the index is a secondary index of a join index that at least partially covers the fact table.

12. The method of claim 11 , further including

recognizing by said computer IN-predicate single column IN-Lists and disjuncted single column conditions residing on the same column.

13. The method of claim 1 , further including

recognizing by said computer single column IN-Lists.

14. The method of claim 1 , further including

recognizing, by said computer, multiple-column IN-Lists.

15. The method of claim 14 further including

recognizing, by said computer, at least one of: a single-column IN-List, a list of disjuncted compound conditions residing in a set of columns, and a combination of one or more single column IN-Lists or multi-column IN-Lists.

16. A database system for accessing a database, the database system including:

a parallel processing system including one or more nodes;

multiple CPUs, each of the one or more nodes providing access to one or more of the CPUs;

multiple virtual processes, each of the one or more CPUs providing access to one or more of the virtual processes, each process configured to manage data stored in one of a plurality of data-storage facilities;

an optimizer for optimizing a database query for a star database schema including at least one fact table and at least one dimension table, in which the database query includes an IN-List condition, the optimizer configured to:

transform the IN-List condition into a relation;

join the IN-List relation with the dimension table to produce a join result; and

joining the join result to the fact table.

17. The database system of claim 16 , where the optimizer is configured to determine whether an IN-List exists within a WHERE clause.

18. The database system of claim 16 , where the optimizer is configured to determine whether an IN-List exists within an ON clause.

19. The database system of claim 16 , where the optimizer is configured to:

evaluate, for each of multiple different join paths, a cost associated with

joining the IN-List relation with the dimension table; and

select a lowest cost path from the different join paths.

20. The database system of claim 16 , where the optimizer is configured to:

evaluate, for each of multiple different join paths, a cost associated with

joining the join result to the fact table; and

select a lowest cost path from the different join paths.

21. The database system of claim 16 , where the optimizer is configured to:

evaluate, for each of multiple different join paths including plans that use IN-List as single table condition and plans that use IN-List as dimension table IN-List star join plan, a cost associated with each join path; and

select a lowest cost path from the different join paths.

22. The database system of claim 16 , where the optimizer is configured to:

identify an index for use in joining the join result to the fact table; and

apply the index when joining the join result to the fact table.

23. The database system of claim 22 in which the index is a primary index of the fact table.

24. The database system of claim 22 in which the index is a secondary index of the fact table.

25. The database system of claim 22 in which the index is a primary index of a join index that at least partially covers the fact table.

26. The database system of claim 22 in which the index is a primary index of a join index that at least partially covers the fact table.

27. The database system of claim 16 , where the optimizer is configured to recognize single column IN-Lists.

28. The database system of claim 16 , where the optimizer is configured to recognize IN-predicate single column IN-Lists and disjuncted single column conditions residing on the same column.

29. The database system of claim 16 , where the optimizer is configured to recognize multiple-column IN-Lists.

30. The database system of claim 16 , where the optimizer is configured to recognize any of: a single-column IN-List, a list of disjuncted compound conditions residing in the same set of columns, and a combination of one or more single column IN-Lists or multi-column IN-Lists.