Profile based set of plans for a database

A computer software product that includes a medium readable by a processor, the medium having stored thereon, a method comprising:

• using a current plan when a query is invoked, the current plan having a corresponding current profile;
• determining when the current profile is changed into a new profile;
• comparing the new profile to a set of stored profiles;
• when the new profile matches a first one of the set of stored profiles:
• set the new profile as the current profile and set a first one of a set of stored plans that corresponds to the first stored profile, as the current plan;
• and
• when the new profile does not match one of the set of stored profiles:
• invoke an optimizer to determine a new plan for the new profile, set the new profile as the current profile, set the new plan as the current plan, save the new plan into the set of stored plans, and save the new profile into the set of stored profiles.

In a database program running on a computer system, a database management system used to select a plan for a query, the database management system comprising:

• means for selecting a current plan when a query is invoked, the current plan having a corresponding current profile;
• means for determining when the current profile is changed into a new profile;
• means for comparing the new profile to a set of stored profiles, wherein the database management system sets the new profile as the current profile and sets a first one of a set of stored plans that corresponds to the first stored profile, as the current plan when the new profile matches a first one of the set of stored profiles;
• and
• wherein the database management invokes an optimizer to determine a new plan for the new profile, sets the new profile as the current profile, sets the new plan as the current plan, saves the new plan into the set of stored plans, and saves the new profile into the set of stored profiles when the new profile does not match one of the set of stored profiles.