PostgreSQL, Second Edition

Returning Complete Rows from an Extension Function

If you've read through the first few sections in this chapter, you know how to write an extension function that returns a single scalar value (that's what the filesize() function does). You also know how to return a set of scalar values (that's what the filelist() function does). In this section, I'll show you how to return a set of rows (or, as the PostgreSQL developers prefer to call them, tuples).

To illustrate the sequence that you must follow to return multiple tuples from an extension function, I'll create a new function, fileinfo(), that combines filesize() and filelist(). You call fileinfo() with the name of a directory and it returns a SETOF tuples. Each tuple contains three columns: ...