Call a function for each row in select - Postgres - postgresql

Question

I have a function called "getList(date)". This function returns me a items list (with several columns) from the date inputted in the parameter.
If I call:
SELECT * FROM getList('12/31/2014');
It works fine. It returns me a list with the date, the item name and the price.
Something like this:
date item_description price
-----------------------------------------------
12/31/2014 banana 1
12/31/2014 apple 2.5
12/31/2014 coconut 3
But I have another table with the dates that I want to search for.
So, I want to select all the dates from that table and, for each row returned, I want to call my function "getList" to have a result like this:
date item_description price
-----------------------------------------------
12/28/2014 banana 0.5
12/28/2014 apple 1.5
12/28/2014 coconut 2
12/31/2014 banana 1
12/31/2014 apple 2.5
12/31/2014 coconut 3
I don't know exactly how to do it. Of course my data is not a fruit list. This is just to explain the whole thing easier.
Thank you very much.

Answer 1

Correct way - LATERAL join
The correct way to do this is with a lateral query (PostgreSQL 9.3 or newer):
SELECT d."date", f.item_description, f.price
FROM mydates d,
LATERAL getList(d."date") f;
See the manual.
Legacy way - SRF in SELECT
In older versions you must use a PostgreSQL extension with some ... quirky ... properties, support for set-returning functions in the SELECT-list. Do not use this unless you know you must support PostgreSQL 9.2 or older.
SELECT d."date", (getList(d."date").*
FROM mydates d;
This may result in multiple-evaluation of the getList function, once for each column of the output.