Reusing database statistics for user aggregate queries

A computer system for determining and providing a plurality of aggregate functions, comprising:

• one or more processors, one or more computer-readable memories, one or more computer-readable tangible storage devices, and program instructions stored on at least one of the one or more storage devices for execution by at least one of the one or more processors via at least one of the one or more memories, wherein the computer system is capable of performing a method comprising:
• scanning at least one database table;
• determining the plurality of aggregate functions associated with the at least one database table;
• storing the determined plurality of aggregate functions on at least one system catalog table;
• providing at least one indication that the stored determined plurality of aggregate functions are valid;
• receiving at least one database query associated with the at least one database table;
• based on the received at least one database query, determining whether the stored determined plurality of aggregate functions are valid;
• in response to the determination that the stored determined plurality of aggregate functions are valid, retrieving the stored determined plurality of aggregate functions from the at least one system catalog;
• in response to the determination that the stored determined plurality of aggregate functions are invalid, re-scanning the at least one database table;
• determining the plurality of aggregate functions based on the re-scanned at least one database table;
• and
• presenting the determined plurality of aggregate functions based on the re-scanned at least one database table and the stored determined plurality of aggregate functions retrieved from the at least one system catalog table to at least one client.

A computer program product for determining and providing a plurality of aggregate functions, comprising:

• one or more computer-readable storage devices and program instructions stored on at least one of the one or more tangible storage devices, the program instructions executable by a processor, the program instructions comprising:
• program instructions to scan at least one database table;
• program instructions to determine the plurality of aggregate functions associated with the at least one database table;
• program instructions to store the determined plurality of aggregate functions on at least one system catalog table;
• program instructions to provide at least one indication that the stored determined plurality of aggregate functions are valid;
• program instructions to receive at least one database query associated with the at least one database table;
• based on the received at least one database query, program instructions to determine whether the stored determined plurality of aggregate functions are valid;
• in response to the determination that the stored determined plurality of aggregate functions are valid, program instructions to retrieve the stored determined plurality of aggregate functions from the at least one system catalog;
• in response to the determination that the stored determined plurality of aggregate functions are invalid, program instructions to re-scanning the at least one database table;
• program instructions to determine the plurality of aggregate functions based on the re-scanned at least one database table;
• and
• program instructions to present the determined plurality of aggregate functions based on the re-scanned at least one database table and the stored determined plurality of aggregate functions retrieved from the at least one system catalog table to at least one client.