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--$Id: census_tracts_functions.sql 7996 2011-10-21 12:01:12Z robe $
/***
*
* Copyright (C) 2012 Regina Obe and Leo Hsu (Paragon Corporation)
**/
-- This function given a geometry try will try to determine the tract.
-- It defaults to returning the tract name but can be changed to return track geoid id.
-- pass in 'tract_id' to get the full geoid, 'name' to get the short decimal name
CREATE OR REPLACE FUNCTION get_tract(IN loc_geom geometry, output_field text DEFAULT 'name')
RETURNS text AS
$$
DECLARE
var_state text := NULL;
var_stusps text := NULL;
var_result text := NULL;
var_loc_geom geometry;
var_stmt text;
var_debug boolean = false;
BEGIN
--$Id: census_tracts_functions.sql 7996 2011-10-21 12:01:12Z robe $
IF loc_geom IS NULL THEN
RETURN null;
ELSE
IF ST_SRID(loc_geom) = 4269 THEN
var_loc_geom := loc_geom;
ELSIF ST_SRID(loc_geom) > 0 THEN
var_loc_geom := ST_Transform(loc_geom, 4269);
ELSE --If srid is unknown, assume its 4269
var_loc_geom := ST_SetSRID(loc_geom, 4269);
END IF;
IF GeometryType(var_loc_geom) != 'POINT' THEN
var_loc_geom := ST_Centroid(var_loc_geom);
END IF;
END IF;
-- Determine state tables to check
-- this is needed to take advantage of constraint exclusion
IF var_debug THEN
RAISE NOTICE 'Get matching states start: %', clock_timestamp();
END IF;
SELECT statefp, stusps INTO var_state, var_stusps FROM state WHERE ST_Intersects(the_geom, var_loc_geom) LIMIT 1;
IF var_debug THEN
RAISE NOTICE 'Get matching states end: % - %', var_state, clock_timestamp();
END IF;
IF var_state IS NULL THEN
-- We don't have any data for this state
RAISE NOTICE 'No data for this state';
RETURN NULL;
END IF;
-- locate county
var_stmt := 'SELECT ' || quote_ident(output_field) || ' FROM tract WHERE statefp = $1 AND ST_Intersects(the_geom, $2) LIMIT 1;';
EXECUTE var_stmt INTO var_result USING var_state, var_loc_geom ;
RETURN var_result;
END;
$$
LANGUAGE plpgsql IMMUTABLE
COST 500;
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