(Much) Faster Unions in PostGIS 1.4

(Much) Faster Unions in PostGIS 1.4

“Originally posted at GeoSpeil.

I have had a very geeky week, working on bringing the “cascaded union” functionality to PostGIS.

By way of background, about a year ago, a PostGIS user brought a question up. He had about 30K polygons he was unioning and the process was taking hours. ArcMap could to it in 20 minutes, what was up? First of all, he had an unbelievably degenerate data set, which really did a great job of exposing the inefficiency of the PostGIS union aggregate. Second, the union aggregate really was inefficient”.

 

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