I discovered this bug while investigating issues with the updates process related to #1190#1292, and #814.
The `transportation_name` layer produces slightly different `tags` hstore values in the `osm_transportation_name_linestring` table during the initial import versus when running an update. As currently written, the import code produces null-value keys in the `tags` column, while the update code suppresses them. This PR removes that difference and makes the import code use same method that is currently used in the update code.
With a test case I've written, the import code produces a tags hstore that looks like this:
`"name"=>"OpenMapTiles Secondary 2", "name:de"=>NULL, "name:en"=>NULL, "name_int"=>"OpenMapTiles Secondary 2", "name:latin"=>"OpenMapTiles Secondary 2"`
...while the update code produces a tags hstore that looks like this:
`"name"=>"OpenMapTiles Secondary 2", "name_int"=>"OpenMapTiles Secondary 2", "name:latin"=>"OpenMapTiles Secondary 2"`
Note the missing NULL values.
This bug causes a small amount of space wastage after an update is run, because the update matching code detects the `tags` value as different, resulting in a duplicate copy of the tags value if that row is updated. This causes duplicate objects and breaks GROUP BY clauses that expect to group same-tagged features together. I've tested this by inspection of a generated mbtiles, database spot checks, and the unit test code included in this PR.
Closes#271
This PR adds track and path rendering at lower zooms than currently provided, and also achieves near-parity with openstreetmap-carto on track and path rendering. A previously-abandoned attempt, with significant discussion, was #1169.
Fixes#1128
This PR adds 6 new columns to the `transportation_name` column, named `route_1` through `route_6`. These columns contain route information for a section of roadway. The value is stored in the form **network=ref**. For example, Interstate 95 in the United States would be `US:I=95`. Thus, each `route_N` value contains enough information to render a highway shield. Since a section of road can be a part of more than one route, the `route_2`, `route_3`, etc, will contain the 2nd, 3rd, etc., concurrent routes.
The technical approach was to extend the change in #1135, which added ordered concurrency indexes to the `osm_route_member` table by joining up to the the first six entries to the `osm_transportation_name_network` table. In addition, that PR provided a ranking system for concurrent highways, ordering first by `network_type` (for example, `us-interstate`, `us-state`, etc), then alphabetically by network name, and then by ref in ascending order. This ordering of concurrent route memberships is now exposed in this PR in the sequential `route_N` values, meaning that rendered concurrent highway shields will be reasonably sorted.
The renderings below were generated using this branch of OpenMapTiles, as well as a separate branch of openstreetmap-americana:
https://github.com/ZeLonewolf/openstreetmap-americana/tree/openmaptilers-new-features-test
The rendering approach is to use the [formatted expressions](https://maplibre.org/maplibre-gl-js-docs/style-spec/expressions/) feature in mapLibre to insert images into a string of text. Blank shields are added to the sprite sheet for all possible route networks. Next, a [styleimagemissing](https://maplibre.org/maplibre-gl-js-docs/api/map/) callback is registered. As each shield ID is requested, the callback retrieves the sprite shield blank associated with the route's network, draw the `ref` text on the shield, and insert the complete shield back into the map.
Of note, this approach currently results in shields which are rotated about the road rather than being viewport aligned. This issue is currently documented as maplibre/maplibre-gl-js#188. A separate repository (https://github.com/ZeLonewolf/maplibre-shield-rotation-sample) has been created as a test case to fix this rotation issue.
Adding route concurrency information to OpenMapTiles would be a major step forward in achieving comprehensive highway shield renderings in a vector map!
**Renderings**:
This PR adds a layer for `highway=motorway_junction` features.
This implementation of highway exits in the transportation_name layer add to the existing layer table structure, and renames the internal column name from "construction" (which was already overloaded with non-construction usages) to "subclass", which will be less confusing to future developers. The string 'junction' is used as the universal sub-class for highway exits.
A new documentation PR has been opened at openmaptiles/www.openmaptiles.org#69 to reflect these changes in the documentation.
Nicholas Skehin
