Execute multiple functions together without losing performance

Question

I have this process that has to make a series of queries, using pl/pgsql:

--process:
SELECT function1();
SELECT function2();
SELECT function3();
SELECT funct         


        

Answer 1

Warning for future readers (2015-05-30).

The technique described in the question is one of the smartest ways to effectively block the server.

In some corporations the use of this technology can meet with the reward in the form of immediate termination of the employment contract.

Attempts to improve this method are useless. It is simple, beautiful and sufficiently effective.

---

In RDMS the support of transactions is very expensive. When executing a transaction the server must create and store information on all changes made to the database to make these changes visible in environment (other concurrent processes) in case of a successful completion, and in case of failure, to restore the state before the transaction as soon as possible. Therefore the natural principle affecting server performance is to include in one transaction a minimum number of database operations, ie. only as much as is necessary.

A Postgres function is executed in one transaction. Placing in it many operations that could be run independently is a serious violation of the above rule.

The answer is simple: just do not do it. A function execution is not a mere execution of a script.

In the procedural languages used to write applications there are many other possibilities to simplify the code by using functions or scripts. There is also the possibility to run scripts with shell.

The use a Postgres function for this purpose would make sense if there were a possibility of using transactions within the function. At present, such a possibility does not exist, although discussions on this issue have already long history (you can read about it e.g. in postgres mailing lists).