PR #1168 removed several `WHERE` clauses in the `transportation_merge_*` table series. With those removed, it appears that `osm_transportation_merge_linestring_gen_z8` and `osm_transportation_merge_linestring` are nearly identical, with the former simply adding an `ST_Simplify()` operation.
A grep of the codebase indicates that the _only_ use for `osm_transportation_merge_linestring` is to hold the intermediate result of an `ST_Dump(geometry))` before it is fed into `ST_Simplify()`. Therefore, it appears that we're holding an entire zoom 8 copy of the transportation layer (all motorway/trunk/primary roads) in a materialized view for absolutely no reason at all.
This PR removes the `osm_transportation_merge_linestring` intermediate table and changes the definition of `osm_transportation_merge_linestring_gen_z8` to perform the `ST_Dump()` and `ST_Simplify()` transformations directly from the `osm_highway_linestring` table in a single operation.
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.
To avoid discontinuous transportation lines between zooms 9 and 11.
- Originally limit geometry by length for z9 - z11 (`ST_Length(geometry) > ZRes(11)`)
- highway z9 to z11 was generalized during import-osm
- now just create a filtered and generalized z11 table
- then merge segments in the same way as from (full-featured) osm_highway_linestring and used this merged z11 for mat.view z10 and z9
Close#1107
Seems like etl and mapping diagrams have been neglected
for a long time. Now it regenerates the files and places
them in the source dir.
This PR also fixes two broken files:
* layers/aerodrome_label/mapping_diagram.png
* layers/housenumber/mapping_diagram.png
They were generated using the newest tools version with the fix
https://github.com/openmaptiles/openmaptiles-tools/pull/65
