Re: [GENERAL] Is PL-PGSQL interpreted or complied?

The PLpgSQL proc are saved in original form - you can see the content of system table pg_proc. Before saving a syntax checking is processed. When PLpgSQL function is executed first time in session, then source code is loaded from pg_proc, and parsed to AST (Abstract syntax tree). AST is stored in session cache. Next, the AST is directly interpreted, repeatedly. 

 

Probably it is possible, but it requires some work - PLpgSQL is just glue for SQL or for SQL expressions. There are not mathematical unit, there are not some like basic library. All is shared with Postgres SQL engine.  This feature is very specific for PLpgSQL. Every expression in PLpgSQL is translated to SELECT - some simple SELECTs are executed in special mode, faster, than usual queries.

PLpgSQL source code https://github.com/postgres/postgres/tree/master/src/pl/plpgsql/src

Regards

Pavel