Introducing Crunchy Data Warehouse: A next-generation Postgres-native data warehouse. Crunchy Data Warehouse Learn more
Paul Ramsey
Paul Ramsey
Beautiful, responsive maps are best built using vector tiles , and PostgreSQL with PostGIS can produce vector tiles on-the-fly . However, to use vector tiles in a beautiful, responsive map, you need to be able to access those tiles over the HTTP web protocol, and you need to be able to request them using a standard XYZ tiled map URL . It's possible to write your own HTTP wrapper for the PostGIS vector tile generator, but you don't need to! pg_tileserv is a lightweight vector tile server s...
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Paul Ramsey
Let's put that on a map! PostGIS has so many cool features that it is possible to do full GIS analyses without ever leaving the SQL language, but... at the end of the day, you want to get those results, show that data, on the map. The Crunchy Data geospatial team has been thinking about how to bring PostGIS to the web, and we established some basic principles: • Use the database, as much as possible. • The database already has a user model and security model. • The database can already generat...
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Paul Ramsey
Where are you? Go ahead and figure out your answer, I'll wait. No matter what your answer, whether you said "sitting in my office chair" or "500 meters south-west of city hall" or "48.43° north by 123.36° west", you expressed your location relative to something else, whether that thing was your office layout, your city, or Greenwich . A geospatial database like PostGIS has to have able to convert between these different reference frames, known as "coordinate reference systems". The math for the...
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Paul Ramsey
While PostGIS includes lots of algorithms and functionality we have built ourselves, it also adds geospatial smarts to PostgreSQL by linking in specialized libraries to handle particular problems: • Proj for coordinate reference support; • GDAL for raster functions and formats; • GEOS for computational geometry (basic operations); • CGAL for more computational geometry (3D operations); and • for format support, libxml2, libjsonc, libprotobuf-c Proj for coordinate reference support; GDAL...
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Paul Ramsey
Parallel query has been a part of PostgreSQL since 2016 with the release of version 9.6 and in theory PostGIS should have been benefiting from parallelism ever since. In practice, the complex nature of PostGIS has meant that very few queries would parallelize under normal operating configurations -- they could only be forced to parallelize using oddball configurations . With PostgreSQL 12 and PostGIS 3, parallel query plans will be generated and executed far more often, because of changes t...
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Paul Ramsey
With the availability of MVT tile format in PostGIS via ST_AsMVT() , more and more people are generating tiles directly from the database. Doing so usually involves a couple common steps: • exposing a tiled web map API over HTTP • converting tile coordinates to ground coordinates to drive tile generation exposing a tiled web map API over HTTP converting tile coordinates to ground coordinates to drive tile generation Tile coordinates consist of three values: • zoom , the level of the tile...
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Paul Ramsey
The raster functionality in PostGIS has been part of the main extension since it was introduced. When PostGIS 3 is released, if you want raster functionality you will need to install both the core extension, and also the extension. Breaking out the raster functionality allows packagers to more easily build stripped down "just the basics" PostGIS without also building the raster dependencies, which include the somewhat heavy GDAL library. The raster functionality remains intact however, a...
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Paul Ramsey
Vector tiles are the new hotness , allowing large amounts of dynamic data to be sent for rendering right on web clients and mobile devices, and making very beautiful and highly interactive maps possible. Since the introduction of ST_AsMVT() , people have been generating their tiles directly in the database more and more, and as a result wanting tile generation to go faster and faster. Every tile generation query has to carry out the following steps: • Gather all the relevant rows for the tile...
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Paul Ramsey
With the release of PostGIS 3.0 , queries that geometry columns will return rows using a Hilbert curve ordering, and do so about twice as fast. Whuuuut!?! The history of "ordering by geometry" in PostGIS is mostly pretty bad. Up until version 2.4 (2017), if you did on a geometry column, your rows would be returned using the ordering of the minimum X coordinate value in the geometry. One of the things users expect of "ordering" is that items that are "close" to each other in the ordered li...
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Paul Ramsey
With PostGIS 3.0, it is now possible to generate GeoJSON features directly without any intermediate code, using the new function. The GeoJSON format is a common transport format, between servers and web clients, and even between components of processing chains. Being able to create useful GeoJSON is important for integrating different parts in a modern geoprocessing application. PostGIS has had an for forever, but it does slightly less than most users really need: it takes in a PostGIS geo...
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