Mastering PostgreSQL 9.6

Understanding function inlining

As outlined in this section already, there are many optimizations which help to speedup queries. One of them is called function inlining. PostgreSQL is able to inline immutable SQL functions. The main idea is to reduce the number of function calls which have to be made to speed things up.

Here is an example of a function:

test=# CREATE OR REPLACE FUNCTION ld(int)  RETURNS numeric AS  $$                 SELECT log(2, $1);                                                                                                                       $$  LANGUAGE 'sql' IMMUTABLE; CREATE FUNCTION

The function will calculate the logarithmus dualis of the input value:

test=# SELECT ld(1024);          ld           ---------------------  10.0000000000000000 (1 row) 

To demonstrate how things work, I will recreate the table with less content to speedup the index creation: