Using optimizer hints v17

When you invoke a DELETE, INSERT, SELECT, or UPDATE command, the server generates a set of execution plans. After analyzing those execution plans, the server selects a plan that generally returns the result set in the least amount of time. The server's choice of plan depends on several factors:

• The estimated execution cost of data handling operations
• Parameter values assigned to parameters in the Query Tuning section of the postgresql.conf file
• Column statistics that were gathered by the ANALYZE command

As a rule, the query planner selects the least expensive plan. You can use an optimizer hint to influence the server as it selects a query plan.