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Mapnik's PluginArchitecture supports the use of different input formats.
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One such plugin supports the sqlite ([SQLite](http://en.wikipedia.org/wiki/SQLite)). The plugin works with two types of geometry storage methods - raw OGC WKB and ([Spatialite](http://www.gaia-gis.it/spatialite)) geometries.
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You can create a pure SQLite + WKB geometry based sqlite db using ogr like:
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ogr2ogr -f SQLite test.sqlite some.shp
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You can create a spatialite enabled db also using ogr:
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ogr2ogr -f SQLite test.sqlite some.shp -dsco SPATIALITE=YES
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For more details see: http://www.gdal.org/ogr/drv_sqlite.html
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The main difference is that a spatialite enabled db will include a spatial index inside the database. A pure SQLite db will not contain a spatial index, but Mapnik can create one on the fly.
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# Parameters
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| *parameter* | *value* | *description* | *default* |
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|:------------------|----------|---------------|----------:|
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| file | string | sqlite database file path | |
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| base | string | optional base path where to search for the sqlite database file | |
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| table | string | name of the table to fetch, this can be a sub-query | |
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| metadata | string | name of the metadata table where the extent and srid of the table are specified | |
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| key_field | string | name of the id field of the table | OGC_FID |
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| geometry_field | string | name of the geometry field, in case you have more than one in a single table | the_geom |
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| extent | string | maxextent of the geometries | determined by querying the metadata table |
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| row_offset | integer | number of rows to skip when querying data | 0 |
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| row_limit | integer | max number of rows to return when querying data, 0 means no limit | 0 |
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| wkb_format | string | type of WKB in the geometry field blob, this can be "generic", "spatialite", or "twkb" | not set, determined automatically by testing for generic (WKB) or spatialite content |
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| use_spatial_index | boolean | choose wheter to use the spatial index when fetching data | true |
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| multiple_geometries | boolean | wheter to use multiple different objects or a single one when dealing with multi-objects (this is mainly related to how the label are used in the map, one label for a multi-polygon or one label for each polygon of a multi-polygon)| false |
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| encoding | string | internal file encoding | utf-8 |
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# Usage
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*Note*:
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* Spatial tables read from sqlite by Mapnik _must_ have a cooresponding entry in `geometry_columns`.
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* Use the `geometry_field` parameter to specify which field to use if you have >1 geometry in the table/query.
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## C++
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Plugin datasource initialization example code can be found on PluginArchitecture.
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A Sqlite datasource may be created as follows:
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```cpp
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{
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parameters p;
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p["type"]="sqlite";
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p["file"]=sqlite_spatial_database_file;
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p["table"]="bridges";
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p["geometry_field"]="geom";
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p["extent"]="2309554.99818767,5024797.73763923,2318414.90507308,5040447.94690007";
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set_datasource(datasource_cache::instance()->create(p));
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// Bridges
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Layer lyr("Bridges");
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lyr.add_style("bridges"); // in style.xml
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m.addLayer(lyr);
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}
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```
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## Further References |
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\ No newline at end of file |
