41 lines
1.6 KiB
PL/PgSQL
41 lines
1.6 KiB
PL/PgSQL
/* Aggregates rivers by name and proximity. */
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drop function if exists aggregate_rivers;
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create function aggregate_rivers() returns table(osm_id bigint, name text, way geometry) as $$
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declare
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c record;
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cc record;
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changed boolean;
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begin
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while (select count(1) from aggregate_rivers_tmp) > 0 loop
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select * from aggregate_rivers_tmp limit 1 into c;
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delete from aggregate_rivers_tmp a where a.osm_id = c.osm_id;
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changed = true;
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while changed loop
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changed = false;
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for cc in (select * from aggregate_rivers_tmp a where a.name = c.name and st_dwithin(a.way, c.way, 500)) loop
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c.way = st_linemerge(st_union(c.way, cc.way));
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delete from aggregate_rivers_tmp a where a.osm_id = cc.osm_id;
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changed = true;
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end loop;
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end loop; -- while changed
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return query select c.osm_id, c.name, c.way;
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end loop; -- count(1) from aggregate_rivers_tmp > 0
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return;
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end
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$$ language plpgsql;
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drop index if exists aggregate_rivers_tmp_id;
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drop index if exists aggregate_rivers_tmp_gix;
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drop table if exists aggregate_rivers_tmp;
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create temporary table aggregate_rivers_tmp (osm_id bigint, name text, way geometry);
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create index aggregate_rivers_tmp_id on aggregate_rivers_tmp(osm_id);
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create index aggregate_rivers_tmp_gix on aggregate_rivers_tmp using gist(way) include(name);
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insert into aggregate_rivers_tmp
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select p.osm_id, p.name, p.way from planet_osm_line p
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where waterway in ('river', 'stream', 'canal') and :where;
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drop table if exists agg_rivers;
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create table agg_rivers as (select * from aggregate_rivers() where st_length(way) >= 50000);
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drop table aggregate_rivers_tmp;
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