tilelive-postgis
Implements the tilelive API for generating mapnik vector tiles from PostGIS.
Installation
npm install @mapbox/tilelive tilelive-postgis
Usage
const tilelive = require('@mapbox/tilelive');
require('tilelive-postgis').registerProtocols(tilelive);
const uri = 'postgis://user:password@localhost:5432/test?table=test_table&geometry_field=geometry&srid=4326';
tilelive.load(uri, (error, source) => {
if (error) throw error;
source.getTile(0, 0, 0, (error, tile, headers) => {
// `error` is an error object when generation failed, otherwise null.
// `tile` contains the compressed image file as a Buffer
// `headers` is a hash with HTTP headers for the image.
});
});
If PostgreSQL server running locally and accepting connections on Unix domain socket, you can connect like this:
const uri = 'postgis:///var/run/postgresql/test?table=test&geometry_field=geom';
tilelive.load(uri, (error, source) => { ... });
You can also use query parameter to specify sub-query like this:
const query = `(select * from schemaName.tableName where st_intersects(geometry, !bbox!)) as query`;
const uri = `postgis://user@localhost/test?table=test_table&geometry_field=geometry&query=${encodeURI(query)}`;
tilelive.load(uri, (error, source) => { ... });
Parameters
The only parameter that is not mapnik specific is:
| parameter | value | description | default |
|---|---|---|---|
| layerName | string | name of the layer in resulting tiles. | defaults to the table name for backwards compatibility. |
Actual list of parameters you can see here.
| parameter | value | description | default |
|---|---|---|---|
| table | string | name of the table to fetch. | |
| geometry_field | string | name of the geometry field, in case you have more than one in a single table. This field and the SRID will be deduced from the query in most cases, but may need to be manually specified in some cases. | |
| geometry_table | string | name of the table containing the returned geometry; for determining RIDs with subselects | |
| srid | integer | srid of the table, if this is > 0 then fetching data will avoid an extra database query for knowing the srid of the table | 0 |
| extent | string | maxextent of the geometries | determined by querying the metadata for the table |
| extent_from_subquery | boolean | evaluate the extent of the subquery, this might be a performance issue | false |
| connect_timeout | integer | timeout is seconds for the connection to take place | 4 |
| persist_connection | boolean | choose whether to share the same connection for subsequent queries | true |
| row_limit | integer | max number of rows to return when querying data, 0 means no limit | 0 |
| cursor_size | integer | if this is > 0 then server cursor will be used, and will prefetch this number of features | 0 |
| initial_size | integer | initial size of the stateless connection pool | 1 |
| max_size | integer | max size of the stateless connection pool | 10 |
| multiple_geometries | boolean | whether 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 |
| encoding | string | internal file encoding | utf-8 |
| simplify_geometries | boolean | whether to automatically reduce input vertices. Only effective when output projection matches (or is similar to) input projection. Available from version 2.1.x up. | false |
| max_async_connection | integer | max number of PostGIS queries for rendering one map in asynchronous mode. Default value (1) has no effect. | 1 |
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