Query costing in a multidimensional database
View Patent ↗The cost of running a query (having a query range) on a multidimensional database may be estimated using a process factors criteria beyond merely the number of affected records. First, a materialized view of the database may be represented as a container of tuples, sorted by key. Then keys may be stepped through, each key representing a mapping of a combination of tuples from the container. At each step, the process may request the next smallest key in the query range greater than or equal to the key of the current step, which results in the tuple in the database whose key is the smallest, greater than or equal to the requested key, and determine if the resulting tuple is in the query range. The cost of the query may then be estimated as the number of tuples upon which the range check was performed.
1. A method comprising:
estimating processing cost for a query on a multidimensional cube, the query having a query range, by:
representing a materialized view as a container of tuples;
wherein each tuple in the materialized view corresponds to a combination of dimension key values for which data exists in said multidimensional cube;
wherein each tuple has a key that is generated based on the set of dimension key values that belong to the tuple;
wherein the tuples are sorted by key;
stepping through all keys for the query range, starting with a smallest key, said smallest key initially being established as a current key and then, at each step:
establishing, as a new current key, a next smallest key that
is in the query range, and
is greater than or equal to the current key;
after establishing the new current key, receiving a resultant tuple that is associated with a resultant key;
wherein the resultant key is a key that
corresponds to a tuple that exists in the materialized view, and
is the smallest key, in the query range key, greater than or equal to the current key;
processing said resultant tuple;
establishing, as a new current key, a key that is incrementally greater than the resultant key; and
estimating the processing cost for the query as equal to the number of tuples upon which said processing was performed during said stepping; and
determining whether or not to materialize the query base upon the estimated processing costs.
2. The method of claim 1 , wherein said container is a B-tree.
3. The method of claim 1 , wherein each member in each dimension of the multidimensional cube has a unique member number.
4. The method of claim 3 , wherein said keys are binary integers constructed from bits of member numbers.
5. A computer-readable storage medium storing instructions which, when executed by a processor, cause the processor to perform the steps of:
estimating processing cost for a query on a multidimensional cube, the query having a query range, by:
representing a materialized view as a container of tuples;
wherein each tuple in the materialized view corresponds to a combination of dimension key values for which data exists in said multidimensional cube;
wherein each tuple has a key that is generated based on the set of dimension key values that belong to the tuple;
wherein the tuples are sorted by key;
stepping through all keys for the query range, starting with a smallest key, said smallest key initially being established as a current key and then, at each step:
establishing, as a new current key, a next smallest key that
is in the query range, and
is greater than or equal to the current key;
after establishing the new current key, receiving a resultant tuple that is associated with a resultant key;
wherein the resultant key is a key that
corresponds to a tuple that exists in the materialized view, and
is the smallest key, in the query range key, greater than or equal to the current key;
processing said resultant tuple;
establishing, as a new current key, a key that is incrementally greater than the resultant key; and
estimating the processing cost for the query as equal to the number of tuples upon which said processing was performed during said stepping; and
determining whether or not to materialize the query base upon the estimated processing costs.
6. The computer-readable storage medium of claim 5 , wherein said container is a B-tree.
7. The computer-readable storage medium of claim 5 , wherein each member in each dimension of the multidimensional cube has a unique member number.
8. The computer-readable storage medium of claim 7 , wherein said keys are binary integers constructed from bits of member numbers.