50 lines
1.5 KiB
PL/PgSQL
50 lines
1.5 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(
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id integer,
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name text,
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way geometry
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) as $$
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declare
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c record;
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cc record;
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changed boolean;
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begin
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while (select count(1) from wm_rivers_tmp) > 0 loop
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select * from wm_rivers_tmp limit 1 into c;
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delete from wm_rivers_tmp a where a.id = c.id;
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changed = true;
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while changed loop
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changed = false;
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for cc in (
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select * from wm_rivers_tmp a where
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a.name = c.name and
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st_dwithin(a.way, c.way, 500)
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) loop
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c.way = st_linemerge(st_union(c.way, cc.way));
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delete from wm_rivers_tmp a where a.id = cc.id;
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changed = true;
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end loop;
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end loop; -- while changed
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return query select c.id, c.name, c.way;
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end loop; -- count(1) from wm_rivers_tmp > 0
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return;
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end
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$$ language plpgsql;
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drop index if exists wm_rivers_tmp_id;
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drop index if exists wm_rivers_tmp_gix;
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drop table if exists wm_rivers_tmp;
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create temporary table wm_rivers_tmp (id serial, name text, way geometry);
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create index wm_rivers_tmp_id on wm_rivers_tmp(id);
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create index wm_rivers_tmp_gix on wm_rivers_tmp using gist(way) include(name);
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insert into wm_rivers_tmp (name, way)
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select p.vardas as name, p.shape as way from :srctable p;
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drop table if exists :dsttable;
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create table :dsttable as (
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select * from aggregate_rivers() where st_length(way) >= 50000
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);
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drop table wm_rivers_tmp;
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