Incorrect layering of breakwater at z=18

[AndrewKvalheim]

Expected behavior

man_made=pier+layer=1 (way 60786491) renders in front of man_made=breakwater (way 942959325).

Actual behavior

At zoom 18, the breakwater renders in front of the pier.

Screenshots illustrating the problem

Correct at zoom 19:

Incorrect at zoom 18:

Correct at zoom 17:

[imagico]

Thanks for the report.

This is not a zoom level problem and has nothing to do with the layer tag. It is because the layers piers-poly and piers-line lack explicit ordering so the drawing order is undefined and varies arbitrarily between tiles and zoom levels.

openstreetmap-carto/project.mml

Lines 365 to 390 in 871804d

	- id: piers-poly
	geometry: polygon
	<<: *extents
	Datasource:
	<<: *osm2pgsql
	table: |-
	(SELECT
	way, man_made
	FROM planet_osm_polygon
	WHERE man_made IN ('pier', 'breakwater', 'groyne')
	) AS piers_poly
	properties:
	minzoom: 12
	- id: piers-line
	geometry: linestring
	<<: *extents
	Datasource:
	<<: *osm2pgsql
	table: |-
	(SELECT
	way, man_made
	FROM planet_osm_line
	WHERE man_made IN ('pier', 'breakwater', 'groyne')
	) AS piers_line
	properties:
	minzoom: 12

Related to #330 by the way.