PostgreSQL 9.3 Lateral Part 1: Use with HStore

One of the improvements coming in PostgreSQL 9.3 is the new LATERAL SQL clause. LATERAL allows you to write more succinct code than you would be able to otherwise and will be a welcome companion to extensions like hstore and PostGIS which both have a plethora of set returning functions. In this article, I'll just demonstrate it's use with hstore and subsequent I'll talk about it's potential use in PostGIS raster,geometry, and topology for exploding subelements.

One thing I was very interested in aside from the succinctness is whether it will be more performant than the older approach. A perfect test case for hstore would be the example we just demonstrated in Unpivoting data in PostgreSQL. For this example, we'll rewrite the hstore view using LATERAL instead of employing a subselect.