PostgreSQL provides a complete programming language called PL/pgSQL, which is integrated with the PostgreSQL trigger system. The PL/pgSQL and SQL languages can be used to code very complex logic. You should use the SQL functions when possible. With the introduction of advanced query writing techniques, such as window functions and lateral joins, in PostgreSQL, we can write very complex logic using only the standard SQL language.
There are several parameters for controlling function behavior in PostgreSQL; these parameters are applicable to the PL/pgSQL and SQL functions, as well. For example, SECURITY DEFINER and SECURITY INVOKER define the execution security context and privileges. The functions' planner parameters help the planner to generate execution plans. These parameters are COST, LEAKPROOF, and ROWS. Configuration related parameters can also be applied to...