Mercurial > gemma
view schema/geo_functions.sql @ 5520:05db984d3db1
Improve performance of bottleneck area calculation
Avoid buffer calculations by replacing them with simple distance comparisons
and calculate the boundary of the result geometry only once per iteration.
In some edge cases with very large numbers of iterations, this reduced
the runtime of a bottleneck import by a factor of more than twenty.
author | Tom Gottfried <tom@intevation.de> |
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date | Thu, 21 Oct 2021 19:50:39 +0200 |
parents | eeeb7bf14217 |
children |
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-- This is Free Software under GNU Affero General Public License v >= 3.0 -- without warranty, see README.md and license for details. -- SPDX-License-Identifier: AGPL-3.0-or-later -- License-Filename: LICENSES/AGPL-3.0.txt -- Copyright (C) 2018, 2019 by via donau -- – Österreichische Wasserstraßen-Gesellschaft mbH -- Software engineering by Intevation GmbH -- Author(s): -- * Sascha L. Teichmann <sascha.teichmann@intevation.de> -- * Tom Gottfried <tom@intevation.de> CREATE OR REPLACE FUNCTION best_utm(g geography) RETURNS integer AS $$ DECLARE center geometry; BEGIN -- Centroid should be calculated on geography to get accurate results -- from lon/lat coordinates, but the respective PostGIS function returns -- POINT(-NaN NaN) for some invalid polygons, while the calculation on -- geometry seems to give reasonable approximations in this context. SELECT ST_Centroid(CAST(g AS geometry)) INTO center; RETURN CASE WHEN ST_Y(center) > 0 THEN 32600 ELSE 32700 END + floor((ST_X(center)+180)/6)::int + 1; END; $$ LANGUAGE plpgsql IMMUTABLE;