FOSS4G North America Hotels

Finding hotels in DC can be a … PITA? Stronger? Hell stroll? Death munch? Face grind? Anyways, our room block at the fabulous Marriott chain is at the reasonable-only-in-DC rate of $189, which is even lower than the government rate. And the block is going away, so if you haven’t booked your room, do it now!

FOSS4G North America is Almost Here: April 10-11

FOSS4G North America is one month away! Due to venue restrictions (400 max!), we only have a limited number of registration spaces still remaining, so sign up soon!

We are proud of our program, which includes talks from open source developers, managers and visionaries. FOSS4G North America is a great opportunity to learn about the statue of the art, and how people are putting open source to use in their organizations. We hope to see you in DC!

FOSS4G NA Community Program Review

It’s that time again (so soon?), time for FOSS4G (North America!) attendees to review the presentation submissions and pick their favourites, so the program committee can build the most appealing (on average) program possible. Head on over to and do your duty!

FOSS4G North America - Presentation Deadline - March 1

Public service announcement! If you’ve been toying with the idea of doing a presentation at FOSS4G North America (April 10-12, in Washington, DS) as I have, it’s time to stop toying and start writing your abstract: the deadline for submissions is this Thursday, March 1.

Go submit your paper right now!

PostGIS vs Oracle Spatial

“That’s a nice database you have there, but how does it compare to Oracle?”

A fair question. On the one hand we have an open source database, with a core development community of a few dozens and a spatial development community of … a few! On the other hand we have a multi-billion dollar IT behemoth with a client list of Fortune 100 companies. On our biases alone, one would expect Oracle to perform much better.

And we’d have to go on our biases, because there haven’t been any Oracle vs PostGIS comparisons available in the wild. Until now.

The Advanced Research Lab for Geospatial Information Science and Engineering of the prestigious Indian Institute of Technology has put a study online, comparing PostGIS to Oracle Spatial across a number of spatial join operations, run in both “cold” (empty cache) and “hot” (pre-seeded cache) modes.

The tests require the database to correctly plan a self-join that includes both spatial and attribute clauses, and then execute. The queries generally seem to require a medium to large quantity of spatial objects to be evaluated in spatial predicate tests. So this is a step up from the usual test of bulk bounding box operations that most benchmarks have gotten bogged down in.

And the results? The authors say:

From the experimental results that we saw, we can conclude that Postgres performs better than Oracle 11g both in the Cold Phase and Warm Phase. Though in few queries Oracle 11g performed better but on the whole Postgres overpowered Oracle 11g. In the warm phase in 3 out of 4 queries Postgres performed significantly well, from this we can conclude that Postgres has better automatic memory management capabilities and page replacement policies… On the whole it is the open-source that wins the game!

Methodologically there are two obvious issues: one is that the Oracle database was on Windows while the PostGIS database was on Linux; the other is that neither database got any tuning, they were both installed and run with default parameters. However, this is one of the nicer comparisons I have read: concise, focussed and with enough technical detail to evaluate what’s going on.

Based on that detail, I can also take a stab at guessing why PostGIS did not win every test: the two slower tests used the touches relationship, which is not optimized in PostGIS using a prepared geometry approach. And the non-optimized predicates in PostGIS are quite inefficient, they calculate far more topological information than is strictly necessary to answer a true/fale question about a single topological relationship. So, more room for improvement!

Thanks to IIT for carrying out and sharing this research, truly invaluable stuff.