Dynamically selecting a data access path to improve query performance

A computer program product comprising:

• a computer readable storage medium having computer readable program code stored on the computer readable storage medium, the computer readable program code being executed by a central processing unit (CPU) of a computer system to cause the computer system to perform a method comprising the steps of:
• the computer system receiving a query which accesses one or more items included in data in a database, the query having multiple conditions whose execution produces a final result of the query;
• the computer system determining amounts of filtering of portions of the data in the database caused by utilizing different types of indexes to filter the portions, respectively;
• the computer system determining respective greatest amounts of filtering for the portions, the greatest amounts of filtering being included in the amounts of filtering;
• the computer system selecting respective types of indexes so that a utilization of a given type of index causes a greatest amount of filtering for a given portion;
• based on the selected types of indexes, the computer system generating respective data access methods for the portions of the data;
• during runtime, the computer system generating respective process tasks for the multiple conditions in the query;
• the computer system controlling an execution flow that executes the process tasks by utilizing the respective data access methods to generate respective initial results;
• and
• the computer system generating the final result of the query by combining the initial results from the process tasks.

A computer system comprising:

• a central processing unit (CPU);
• a memory coupled to the CPU;
• and
• a computer readable storage medium coupled to the CPU, the computer readable storage medium containing instructions that are executed by the CPU via the memory to implement a method comprising the steps of:
• the computer system receiving a query which accesses one or more items included in data in a database, the query having multiple conditions whose execution produces a final result of the query;
• the computer system determining amounts of filtering of portions of the data in the database caused by utilizing different types of indexes to filter the portions, respectively;
• the computer system determining respective greatest amounts of filtering for the portions, the greatest amounts of filtering being included in the amounts of filtering;
• the computer system selecting respective types of indexes so that a utilization of a given type of index causes a greatest amount of filtering for a given portion;
• based on the selected types of indexes, the computer system generating respective data access methods for the portions of the data;
• during runtime, the computer system generating respective process tasks for the multiple conditions in the query;
• the computer system controlling an execution flow that executes the process tasks by utilizing the respective data access methods to generate respective initial results;
• and
• the computer system generating the final result of the query by combining the initial results from the process tasks.