mapnik-org/mapnik — Issue #751: datasources should promise globally unique integer feature id's
Author: artemp
Created: 2011-10-11 08:10:51+00:00
State: open
Labels: Core_Library

Currently the feature.id() can sometimes means different things between datasources.

Shape.input can promise globally unique ids, if the shapefile authoring tool wrote a valid file.

Ogr.input can also promise unique ids for (likely) most datasources it supports, but not for geojson unless a property exists named "id" that is an integer and unique.

SQLite has a built in rowid that is globally unique, but for rtree indexes to work with subqueries we still need to autodetect its name: #821

Postgis.input just increments a count, so we need to add a key_field argument (done/fixed in r3056) so the user can supply the primary key field, or detect it automatically (#804)

Ideally all plugins would provide globally unique feature ids.