Here we give a short overview of the stages a query has to pass in order to obtain a result.

The parser stage consists of two parts: The parser defined in gram

PostgreSQL is implemented using a simple "process per user" client/server model. In this model there is one

The executor takes the plan created by the planner/optimizer and recursively processes it to extract the required set of rows. This is essentially

The task of the planner/optimizer is to create an optimal execution plan. A given SQL query (and hence, a query tree) can be actually executed in a

The examples shown below use tables in the PostgreSQL regression test database. The outputs shown are taken from version 8.3. The behavior

PostgreSQL supports a powerful rule system for the specification of views and ambiguous