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add note about geometry type filtering support new in 2.1.x

springmeyer 2012-07-25 14:52:27 -07:00
parent e90feac246
commit ceb6838382
1 changed files with 12 additions and 8 deletions
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Filter.md

@ -1,9 +1,6 @@
<!-- Name: Filter -->
<!-- Version: 10 -->
<!-- Last-Modified: 2011/08/29 09:04:20 -->
<!-- Author: MaZderMind -->
# Filter # Filter
Each Style-Rule can optionally have a Filter attached. Mapnik walks through all Rules of a Style and checks if it has a Filter specified and if this Filter matches the Object currently rendered. Filters compare an Objects Key-Value Information against the specified rules. When the Datasource is a Postgis Database, the Filter operates on the tables columns, for Shapefiles the Attributes are used.
Each Style-Rule can optionally have a Filter attached. Mapnik walks through all Rules of a Style and checks if it has a Filter specified and if this Filter matches the Object currently rendered. Filters compare a Feature's attributes against the specified rules. When the Datasource is a Postgis Database, the Filter operates on the tables columns, for Shapefiles the dbf columns are used.
In XML [character entities](http://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references) are used to construct filters. You can use the following characters to specify value-comparisons: In XML [character entities](http://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references) are used to construct filters. You can use the following characters to specify value-comparisons:
@ -19,10 +16,9 @@ Filters can be combined with the following operators:
* A `or` B * A `or` B
* `not` A * `not` A
And be combined to complex rules using brackets: `(` and `)`. And they can be combined in complex rules using brackets: `(` and `)`.
Missing Attributes are treated as empty strings. Attributes can be compared against [Regular expressions](http://en.wikipedia.org/wiki/Regular_expression) using the `.match` operator.
Attributes can be compared against [Regular expressions](http://en.wikipedia.org/wiki/Regular_expression) using the `.match` operator.
## Examples in XML ## Examples in XML
Matches all Objects that have an attribute "amenity" with a value of "restaurant": Matches all Objects that have an attribute "amenity" with a value of "restaurant":
@ -31,6 +27,14 @@ Matches all Objects that have an attribute "amenity" with a value of "restaurant
<Filter>[amenity] = 'restaurant'</Filter> <Filter>[amenity] = 'restaurant'</Filter>
``` ```
NEW in Mapnik 2.1.x: Matches all features that contain point geometries:
```xml
<Filter>[mapnik::geometry_type]=point</Filter>
```
Note: the geometry types that can be matched include: `point`,`linestring`,`polygon`, or `collection` (multiple different types per feature).
Matches all Objects that have an attribute "CARTO" with a value that compares greater or equal 2 and lower then 5: Matches all Objects that have an attribute "CARTO" with a value that compares greater or equal 2 and lower then 5:
```xml ```xml