Mastering PostgreSQL 9.6

Using cached plans

In PostgreSQL, a query is executed using four stages:

• The parser: It checks the syntax
• Rewrite system: It take cares of rules, and so on
• Optimizer/planner: It optimizes the query
• Executor: It executes the plan provided by the planner

If the query is short, the first three steps are relatively time consuming compared to the real execution time. Therefore, it can make sense to cache execution plans. PL/pgSQL basically does all the plan caching for you automatically behind the scenes. You don't have to care. PL/Perl and PL/Python will give you the choice. The SPI interface provides functions to handle and run prepared queries, so the programmer has the choice whether a query should be prepared or not. In the case of long ...