4d6945b935
I was reading through the SQL used to generalise the landcover layer ([`layers/landcover/generalized.sql`](596f44aa26/layers/landcover/generalized.sql)) and I noticed that when creating the generalised landcover tables for zooms 9-13, the SQL was doing something like this: ```sql SELECT * FROM simplify_vw_z13 WHERE ST_NPoints(geometry) < 50 UNION ALL SELECT * FROM simplify_vw_z13 WHERE ST_NPoints(geometry) >= 50 AND ST_NPoints(geometry) < 300 ``` As in, the simplification/clustering of landcover generalisations was being done in two steps: once for polygons with fewer than fifty points, and once for polygons with 50+ points. As far as I can see, there's no benefit to doing this — it's probably just an artefact of the dev work done for the [original pull request](https://github.com/openmaptiles/openmaptiles/pull/1035). Of course, I might be completely missing the reason for clustering polygons into two groups (<50 points and 50+ points). But assuming I haven't, I've created this pull request to simplify the SQL used in the generalisation, merging the two steps into something like this: ```sql SELECT * FROM simplify_vw_z13 WHERE ST_NPoints(geometry) < 300 ``` The effect is to slightly reduce the number of landcover features (polygons with <50 points can now be clustered/unioned with those 50+), and to reduce the time taken to generalise the landcover tables (in a small test using OSM's Iceland data I saw a 7% reduction in the time spent). It doesn't alter the features that are shown on the map. Builds upon work from commits4a1b0afa26andda689f9e42.
287 lines
8.6 KiB
SQL
287 lines
8.6 KiB
SQL
DROP TABLE IF EXISTS osm_landcover_gen_z7;
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DROP TABLE IF EXISTS osm_landcover_gen_z8;
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DROP TABLE IF EXISTS osm_landcover_gen_z9;
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DROP TABLE IF EXISTS osm_landcover_gen_z10;
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DROP TABLE IF EXISTS osm_landcover_gen_z11;
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DROP TABLE IF EXISTS osm_landcover_gen_z12;
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DROP TABLE IF EXISTS osm_landcover_gen_z13;
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DROP TABLE IF EXISTS simplify_vw_z7 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z8 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z9 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z10 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z11 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z12 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z13 CASCADE;
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-- etldoc: osm_landcover_polygon -> simplify_vw_z13
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CREATE TABLE simplify_vw_z13 AS
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(
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SELECT subclass,
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ST_MakeValid(
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ST_SnapToGrid(
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ST_SimplifyVW(geometry, power(zres(13),2)),
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0.001)) AS geometry
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FROM osm_landcover_polygon
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WHERE ST_Area(geometry) > power(zres(10),2)
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);
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CREATE INDEX ON simplify_vw_z13 USING GIST (geometry);
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-- etldoc: simplify_vw_z13 -> osm_landcover_gen_z13
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CREATE TABLE osm_landcover_gen_z13 AS
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(
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SELECT subclass, ST_MakeValid((ST_dump(ST_Union(geometry))).geom) AS geometry
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FROM (
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SELECT subclass,
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ST_ClusterDBSCAN(geometry, eps := 0, minpoints := 1) over () AS cid, geometry
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FROM simplify_vw_z13
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WHERE ST_NPoints(geometry) < 300
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AND subclass IN ('wood', 'forest')) union_geom300
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GROUP BY subclass,
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cid
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UNION ALL
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SELECT subclass,
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geometry
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FROM simplify_vw_z13
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WHERE (ST_NPoints(geometry) >= 300 AND subclass IN ('wood', 'forest'))
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OR (subclass NOT IN ('wood', 'forest'))
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);
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CREATE INDEX ON osm_landcover_gen_z13 USING GIST (geometry);
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-- etldoc: simplify_vw_z13 -> simplify_vw_z12
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CREATE TABLE simplify_vw_z12 AS
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(
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SELECT subclass,
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ST_MakeValid(
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ST_SnapToGrid(
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ST_SimplifyVW(geometry, power(zres(12),2)),
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0.001)) AS geometry
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FROM simplify_vw_z13
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WHERE ST_Area(geometry) > power(zres(9),2)
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);
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CREATE INDEX ON simplify_vw_z12 USING GIST (geometry);
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-- etldoc: simplify_vw_z12 -> osm_landcover_gen_z12
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CREATE TABLE osm_landcover_gen_z12 AS
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(
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SELECT subclass, ST_MakeValid((ST_dump(ST_Union(geometry))).geom) AS geometry
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FROM (
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SELECT subclass,
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ST_ClusterDBSCAN(geometry, eps := 0, minpoints := 1) over () AS cid, geometry
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FROM simplify_vw_z12
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WHERE ST_NPoints(geometry) < 300
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AND subclass IN ('wood', 'forest')) union_geom300
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GROUP BY subclass,
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cid
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UNION ALL
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SELECT subclass,
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geometry
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FROM simplify_vw_z12
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WHERE (ST_NPoints(geometry) >= 300 AND subclass IN ('wood', 'forest'))
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OR (subclass NOT IN ('wood', 'forest'))
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);
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CREATE INDEX ON osm_landcover_gen_z12 USING GIST (geometry);
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-- etldoc: simplify_vw_z12 -> simplify_vw_z11
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CREATE TABLE simplify_vw_z11 AS
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(
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SELECT subclass,
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ST_MakeValid(
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ST_SnapToGrid(
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ST_SimplifyVW(geometry, power(zres(11),2)),
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0.001)) AS geometry
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FROM simplify_vw_z12
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WHERE ST_Area(geometry) > power(zres(8),2)
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);
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CREATE INDEX ON simplify_vw_z11 USING GIST (geometry);
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-- etldoc: simplify_vw_z11 -> osm_landcover_gen_z11
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CREATE TABLE osm_landcover_gen_z11 AS
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(
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SELECT subclass, ST_MakeValid((ST_dump(ST_Union(geometry))).geom) AS geometry
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FROM (
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SELECT subclass,
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ST_ClusterDBSCAN(geometry, eps := 0, minpoints := 1) over () AS cid, geometry
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FROM simplify_vw_z11
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WHERE ST_NPoints(geometry) < 300
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AND subclass IN ('wood', 'forest')) union_geom300
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GROUP BY subclass,
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cid
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UNION ALL
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SELECT subclass,
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geometry
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FROM simplify_vw_z11
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WHERE (ST_NPoints(geometry) >= 300 AND subclass IN ('wood', 'forest'))
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OR (subclass NOT IN ('wood', 'forest'))
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);
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CREATE INDEX ON osm_landcover_gen_z11 USING GIST (geometry);
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-- etldoc: simplify_vw_z11 -> simplify_vw_z10
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CREATE TABLE simplify_vw_z10 AS
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(
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SELECT subclass,
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ST_MakeValid(
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ST_SnapToGrid(
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ST_SimplifyVW(geometry, power(zres(10),2)),
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0.001)) AS geometry
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FROM simplify_vw_z11
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WHERE ST_Area(geometry) > power(zres(8),2)
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);
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CREATE INDEX ON simplify_vw_z10 USING GIST (geometry);
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-- etldoc: simplify_vw_z10 -> osm_landcover_gen_z10
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CREATE TABLE osm_landcover_gen_z10 AS
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(
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SELECT subclass, ST_MakeValid((ST_dump(ST_Union(geometry))).geom) AS geometry
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FROM (
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SELECT subclass,
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ST_ClusterDBSCAN(geometry, eps := 0, minpoints := 1) over () AS cid, geometry
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FROM simplify_vw_z10
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WHERE ST_NPoints(geometry) < 300
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AND subclass IN ('wood', 'forest')) union_geom300
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GROUP BY subclass,
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cid
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UNION ALL
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SELECT subclass,
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geometry
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FROM simplify_vw_z10
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WHERE (ST_NPoints(geometry) >= 300 AND subclass IN ('wood', 'forest'))
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OR (subclass NOT IN ('wood', 'forest'))
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);
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CREATE INDEX ON osm_landcover_gen_z10 USING GIST (geometry);
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-- etldoc: simplify_vw_z10 -> simplify_vw_z9
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CREATE TABLE simplify_vw_z9 AS
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(
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SELECT subclass,
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ST_MakeValid(
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ST_SnapToGrid(
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ST_SimplifyVW(geometry, power(zres(9),2)),
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0.001)) AS geometry
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FROM simplify_vw_z10
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WHERE ST_Area(geometry) > power(zres(7),2)
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);
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CREATE INDEX ON simplify_vw_z9 USING GIST (geometry);
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-- etldoc: simplify_vw_z9 -> osm_landcover_gen_z9
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CREATE TABLE osm_landcover_gen_z9 AS
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(
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SELECT subclass, ST_MakeValid((ST_dump(ST_Union(geometry))).geom) AS geometry
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FROM (
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SELECT subclass,
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ST_ClusterDBSCAN(geometry, eps := 0, minpoints := 1) over () AS cid, geometry
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FROM simplify_vw_z9
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WHERE ST_NPoints(geometry) < 300
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AND subclass IN ('wood', 'forest')) union_geom300
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GROUP BY subclass,
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cid
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UNION ALL
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SELECT subclass,
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ST_MakeValid(
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(ST_Dump(
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ST_Union(geometry))).geom) AS geometry
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FROM (
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SELECT subclass,
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ST_ClusterDBSCAN(geometry, eps := 0, minpoints := 1) over () AS cid, geometry
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FROM simplify_vw_z9
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WHERE ST_NPoints(geometry) >= 300
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AND subclass IN ('wood', 'forest')) union_geom_rest
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GROUP BY subclass,
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cid
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UNION ALL
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SELECT subclass,
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geometry
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FROM simplify_vw_z9
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WHERE subclass NOT IN ('wood', 'forest')
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);
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CREATE INDEX ON osm_landcover_gen_z9 USING GIST (geometry);
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-- etldoc: simplify_vw_z9 -> simplify_vw_z8
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CREATE TABLE simplify_vw_z8 AS
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(
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SELECT subclass,
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ST_MakeValid(
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ST_SnapToGrid(
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ST_SimplifyVW(geometry, power(zres(8),2)),
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0.001)) AS geometry
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FROM simplify_vw_z9
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WHERE ST_Area(geometry) > power(zres(6),2)
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);
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CREATE INDEX ON simplify_vw_z8 USING GIST (geometry);
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-- etldoc: simplify_vw_z8 -> osm_landcover_gen_z8
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CREATE TABLE osm_landcover_gen_z8 AS
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(
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SELECT subclass,
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ST_MakeValid(
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(ST_Dump(
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ST_Union(geometry))).geom) AS geometry
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FROM
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(
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SELECT subclass,
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ST_ClusterDBSCAN(geometry, eps := 0, minpoints := 1) OVER () AS cid,
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geometry
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FROM simplify_vw_z8
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) union_geom
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GROUP BY subclass,
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cid
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UNION ALL
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SELECT subclass,
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geometry
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FROM simplify_vw_z8
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WHERE subclass NOT IN ('wood', 'forest')
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);
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CREATE INDEX ON osm_landcover_gen_z8 USING GIST (geometry);
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-- etldoc: simplify_vw_z8 -> simplify_vw_z7
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CREATE TABLE simplify_vw_z7 AS
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(
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SELECT subclass,
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ST_MakeValid(
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ST_SnapToGrid(
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ST_SimplifyVW(geometry, power(zres(7),2)),
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0.001)) AS geometry
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FROM simplify_vw_z8
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WHERE ST_Area(geometry) > power(zres(5),2)
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);
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CREATE INDEX ON simplify_vw_z7 USING GIST (geometry);
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-- etldoc: simplify_vw_z7 -> osm_landcover_gen_z7
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CREATE TABLE osm_landcover_gen_z7 AS
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(
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SELECT subclass,
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ST_MakeValid(
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(ST_Dump(
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ST_Union(geometry))).geom) AS geometry
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FROM
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(
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SELECT subclass,
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ST_ClusterDBSCAN(geometry, eps := 0, minpoints := 1) OVER () AS cid,
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geometry
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FROM simplify_vw_z7
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) union_geom
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GROUP BY subclass,
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cid
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);
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CREATE INDEX ON osm_landcover_gen_z7 USING GIST (geometry);
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DROP TABLE IF EXISTS simplify_vw_z7 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z8 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z9 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z10 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z11 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z12 CASCADE;
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DROP TABLE IF EXISTS simplify_vw_z13 CASCADE;
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