VectorTiles generated via the [openmaptiles-tools](https://github.com/openmaptiles/openmaptiles-tools) toolchain and using the OpenMaptiles-SQL-Layers as the query-source result in tiles which can contain duplicated keys.
This is because PostGIS `ST_AsMVT` is used to generate the Tiles and due to the way they [implemented parallelization](https://trac.osgeo.org/postgis/ticket/4310).
Although it is not prohibited by the Mapbox-Vector-Tile-Specification MapBox as well as MapLibre depending on version either throw a lot of warnings or even crash when encountering tiles with duplicated keys.
https://github.com/mapbox/vector-tile/issues/55https://github.com/maplibre/maplibre-native/issues/795
After investigating I identified the boundary layer in zoom-leves 1 - 4 as the only layers containing duplicated keys.
Fixes#1156Fixes#810Fixes#1228
This PR replaces `osmborder`, which is no longer maintained, with `imposm` mappings and SQL code to generate borders. Key features that were moved into the imposm/SQL layer:
1. Grouping by `osm_id` and aggregating by lowest `admin_level` value so that there's only one copy of ways that are members of multiple relations.
2. Filtering out of point features in boundary relations (typically `admin_centre` and `label` roles).
3. Move disputed boundary detection logic into SQL.
This will increase the database size slightly because of the limits of what imposm can do, as some of the filtering is done in the SQL layer after importing, rather than being done in `osmborder`.
Fixes#1055
This PR moves Natural Earth zoom 7.7 boundary lines into zoom 4.
> Hi, thank you for PR. In github-actions statistics there is a pretty high size increase in zooms 3, 2, 1, which are using data from zoom 4. Maybe keep your change to move `min_zoom <= 7.7` just for zoom 4, but for zoom 3 add a condition `min_zoom <= 7` (that subsequently the condition bubbles into zoom 2 and 1). What do you think?
I agree that this makes sense, and thank you for pointing it out. It didn't occur to me that the zoom 1-3 tables were unbounded. I made the change to pull the `min_zoom` column into the zoom 4 generalized table and filter for `min_zoom< 7`.
With this change, here is Algeria, zoom 3:
Algeria, zoom 4:
This PR adds state name to national borders (`admin_level=2`)
From zoom level 3 there is an added `adm0_l` and `adm0_r` attribute for national borders.
There is 3 main steps:
1) union border lines from OSM and keep separate LineString between intersects
2) create polygons from step 1), create a point in each state polygon, add to this point a state abbreviation from NaturalEarth Data
3) create a short parallel line on the left and right of a small part of the border in 70m distance, and add information about which state overlap this short line.
* Change NE 50m by NE 10m state provinces dataset
* update documentation
Fixes#977
This PR implements the change discussed at #977 to replace Natural Earth 10m states and provinces by the 50m version, since the 10m only covers state borders for US, Canada, Brazil, and Australia.
A few remarks:
* This change only affects zooms 1 to 4, not making any change in borders based in the `OSM Borders` source.
* The `min_zoom<=7` shows the first level regions (level 4 in OSM) as you can check for example for France, Italy, or Spain.
* I don't think it's necessary to simplify the geometries, it would mean adding a new materialized view, or a slower tile generation process.
* This change does not need any change in the styles, even someone could argue it could be interesting to add the country code in this layer as a new field, allowing style editors to filter features by country, but I would prefer to leave that change for another PR.
`disputed_name` is filled for disputed lines of NaturalEarth sources - it contains `ogc_fid` as suggested in https://github.com/openmaptiles/openmaptiles/issues/964. This way it is possible to filter disputed lines in style.
* All functions that access database must be declared as `STABLE`, not `IMMUTABLE` -- because database can change at any moment, e.g. during an update
* there are a few functions that could be made `STRICT` -- passing `NULL` as a parameter will always result in a `NULL`, but for some reason that causes a significant decrease in perf.
* tagged one function as parallel safe
NOTE: somehow `ST_AsMVT()` method of tile generation is showing 70-90% slowdown with this patch. I am not sure of why this is happening. If the reason is the `IMMUTABLE` -> `STABLE` change, we may have to dig deeper into PG optimization
I would like to reformat all of our SQL to have a concise coding style.
This makes it far easier to understand the code for a casual contributor,
and lets us spot errors more easily.
Most importantly, it makes it much easier to grep (search) the code because it is more likely to be in the same syntax
Some key changes:
* SQL keywords are always UPPERCASE, e.g. `SELECT WHEN AS END ...`
* types, variables, aliases, and field names (identifiers) are always lower case
* `LANGUAGE 'plpgsql'` is now `LANGUAGE plpgsql` (no quotes)
* a few minor spacing/semicolon cleanups
P.S. Per @TomPohys request, `TABLE` is spelled using upper case despite being a type for consistency with PG Docs. Same for `LANGUAGE SQL` vs `LANGUAGE plpgsql`.
This PR allows queries to be parallelized on recent versions of Postgres. The `PARALLEL SAFE` modifier has been added to the layer functions and a PLPGSQL function to convert strings into number has been replaced.
`PARALLEL SAFE` is a modifier for `CREATE FUNCTION` available since Postgres 9.6, so this change does not break current OpenMapTiles supported database version. More details about this topic [here](https://www.postgresql.org/docs/current/parallel-safety.html) and at the reference documentation for [`CREATE FUNCTION`](https://www.postgresql.org/docs/current/sql-createfunction.html).
### Testing procedure
The procedure to test this was:
* Imported `spain.pbf` in a clean environment
* Dumped the OpenMapTiles database from the Postgres Docker image
* Created a clean Postgres 12 database using the default Docker image
* Installed `postgis` 3 from the default Debian package and `osml10n` 2.5.8 from the repository (`make`, etc.)
* Restored the dump
* Lowered the postgres planner parameters for triggering parallel plans:
```sql
set parallel_setup_cost = 5;
set parallel_tuple_cost = 0.005;
```
* Manually added the `PARALLEL SAFE` modifier to each function involved in layer queries (not on updates or inserting functions).
* For each layer, run a testing query to confirm parallel workers were created, something like this:
```sql
explain analyze
select * from layer_aerodrome_label(tilebbox(8,128,95),10,null)
union all
select * from layer_aerodrome_label(tilebbox(8,128,97),10,null);
```
* After all the layers were processed and confirmed to start parallel executions, a more complete example was run. This example just retrieves the geometries for all the layers from the same tile but without using any MVT related function.
<details><summary>Testing query</summary>
```sql
-- Using the function layer_landuse
explain analyze
select geometry from layer_water(tilebbox(14,8020,6178),14)
union all
select geometry from layer_waterway(tilebbox(14,8020,6178),14)
union all
select geometry from layer_landcover(tilebbox(14,8020,6178),14)
union all
select geometry from layer_landuse(tilebbox(14,8020,6178),14)
union all
select geometry from layer_mountain_peak(tilebbox(14,8020,6178),14)
union all
select geometry from layer_park(tilebbox(14,8020,6178),14)
union all
select geometry from layer_boundary(tilebbox(14,8020,6178),14)
union all
select geometry from layer_aeroway(tilebbox(14,8020,6178),14)
union all
select geometry from layer_transportation(tilebbox(14,8020,6178),14)
union all
select geometry from layer_building(tilebbox(14,8020,6178),14)
union all
select geometry from layer_water_name(tilebbox(14,8020,6178),14)
union all
select geometry from layer_transportation_name(tilebbox(14,8020,6178),14)
union all
select geometry from layer_place(tilebbox(14,8020,6178),14)
union all
select geometry from layer_housenumber(tilebbox(14,8020,6178),14)
union all
select geometry from layer_poi(tilebbox(14,8020,6178),14)
union all
select geometry from layer_aerodrome_label(tilebbox(14,8020,6178),14);
```
</details>
You can inspect the execution plan and results on [this page](https://explain.dalibo.com/plan/3z). Also [attaching](https://github.com/openmaptiles/openmaptiles/files/3951822/explain-tile-simple.tar.gz) the query and JSON output for future reference. The website gives a ton of details, but you may want to search for nodes mentioning `workers` or `parallel` like in this area referring to `osm_border` or `osm_aeroway_linestring` entities
### Next steps
Since the execution plan is not showing a parallel append at the top level, meaning it's not running each layer individually, I want to continue experimenting with parameters and queries to see if it's possible to even parallelize more the request.
I will post my finding here, even no change in the code should happen.
cc. @nyurik
Co-authored-by: Yuri Astrakhan <yuriastrakhan@gmail.com>
* Move simplified border tables to OMT as MAT VIEWs
Consolidate derived table creation in OMT repository.
Move all non-original simplified geometry tables from import-osmborder
image to this repo, allowing further optimization.
Later we can remove derived table creation fro mthe import-osmborder image.
Natural earth has released new data and now some sql query are invalid
should fix#352
I don't really know how natural earth data versioning is maintained
though 😕
benedikt-brandtner-bikemap
