Switch to Lua transforms and change database schema

.travis.yml

@@ -2,6 +2,10 @@ language: node_js
 sudo: false
 node_js:
   - "0.10"
+addons:
+  apt:
+    packages:
+    - lua5.1
 env:
   - CARTO=0.16.0 MAPNIK='3.0.0 3.0.12'
   - CARTO=0.16.3 MAPNIK='3.0.0 3.0.12'
@@ -16,3 +20,5 @@ script:
   - for m in $MAPNIK; do ./node_modules/carto/bin/carto -a $m project.mml | xmllint - | wc -l; done
   # Validate that the SVGs are valid XML
   - find symbols/ -name '*.svg' | xargs xmllint --noout
+  # Check the Lua transforms
+  - lua scripts/lua/test.lua

CONTRIBUTING.md

@@ -17,6 +17,16 @@ contain a cropped screenshot of the problem, and a link to the area. Don't assum
 that we will see exactly what you see. If a particular OSM object is an issue,
 the issue should contain the tagging of the object.
 
+## 3.x compatibility
+
+OpenStreetMap Carto is currently maintaining compatibility in the output of 3.x
+and 4.x to allow users to smoothly transition and reload their databases. Pull
+requests which cannot be backported to 3.x are not being accepted at this time
+and will be closed.
+
+Whenever a pull request is merged into master, it also needs to be backported to
+the 3.x branch at the same time by the person merging.
+
 ## Easy pickings
 
 Some [easy issues](https://github.com/gravitystorm/openstreetmap-carto/issues?q=is%3Aopen+is%3Aissue+label%3Aeasy) have been selected
@@ -115,6 +125,8 @@ Because SQL within JSON or YAML will not generally be syntax highlighted, indent
 * Add indentation if necessary for complex function calls, WHERE parenthesis, and CASE statements
 * One space before and after = etc
 * Name SQL subqueries after the layer name (but use underscores)
+* When extracting tags from hstore, use `tags->'foo'`, not `tags -> 'foo'`, and only add parenthesis if needed for order of operations
+* To check if a tag is in the tags hstore, use `tags @> 'foo=>bar'`, relying on automatic conversion from `text` to `hstore`.
 
 ## Map Icon Guidelines
 

INSTALL.md

@@ -3,10 +3,10 @@
 ## OpenStreetMap data
 You need OpenStreetMap data loaded into a PostGIS database (see below for [dependencies](#dependencies)). These stylesheets currently work only with the osm2pgsql defaults (i.e. database name is `gis`, table names are `planet_osm_point`, etc).
 
-It's probably easiest to grab an PBF of OSM data from [Mapzen](https://mapzen.com/metro-extracts/) or [geofabrik](http://download.geofabrik.de/). Once you've set up your PostGIS database, import with osm2pgsql:
+Start by setting up your database to have PostGIS and hstore with ``psql -d gis -c 'CREATE EXTENSION postgis; CREATE EXTENSION hstore;'``, then grab some OSM data. It's probably easiest to grab an PBF of OSM data from [Mapzen](https://mapzen.com/metro-extracts/) or [geofabrik](http://download.geofabrik.de/). Once you've done that, import with osm2pgsql:
 
 ```
-osm2pgsql -d gis ~/path/to/data.osm.pbf --style openstreetmap-carto.style
+osm2pgsql -G --hstore --style openstreetmap-carto.style --tag-transform-script openstreetmap-carto.lua -d gis ~/path/to/data.osm.pbf
 ```
 
 You can find a more detailed guide to setting up a database and loading data with osm2pgsql at [switch2osm.org](http://switch2osm.org/loading-osm-data/).

README.md

@@ -76,10 +76,9 @@ and issues have their own [tag](https://github.com/gravitystorm/openstreetmap-ca
 
 Initial releases will not make use of the new features, maintaining compatibility
 with v3.x and v3.x releases will continue with backports, allowing the style to be
-rendered from either a new database or an old one.
-
-When sufficient time has passed for users to reload their databases, new features
-can be used and 3.x compatibility will not be maintained.
+rendered from either a new database or an old one. In order to allow time for users
+to reload their databases, this will be maintained until at least two MINOR
+releases have occurred. After that compatibility will not be maintained.
 
 # Alternatives