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-- location_extract(streetAddressString, stateAbbreviation)
-- This function extracts a location name from the end of the given string.
-- The first attempt is to find an exact match against the place_lookup
-- table. If this fails, a word-by-word soundex match is tryed against the
-- same table. If multiple candidates are found, the one with the smallest
-- levenshtein distance from the given string is assumed the correct one.
-- If no match is found against the place_lookup table, the same tests are
-- run against the countysub_lookup table.
--
-- The section of the given string corresponding to the location found is
-- returned, rather than the string found from the tables. All the searching
-- is done largely to determine the length (words) of the location, to allow
-- the intended street name to be correctly identified.
CREATE OR REPLACE FUNCTION location_extract(fullStreet VARCHAR, stateAbbrev VARCHAR) RETURNS VARCHAR
AS $_$
DECLARE
ws VARCHAR;
location VARCHAR;
lstate VARCHAR;
stmt VARCHAR;
street_array text[];
word_count INTEGER;
rec RECORD;
best INTEGER := 0;
tempString VARCHAR;
BEGIN
IF fullStreet IS NULL THEN
RETURN NULL;
END IF;
ws := E'[ ,.\n\f\t]';
IF stateAbbrev IS NOT NULL THEN
lstate := statefp FROM state_lookup WHERE abbrev = stateAbbrev;
END IF;
lstate := COALESCE(lstate,'');
street_array := regexp_split_to_array(fullStreet,ws);
word_count := array_upper(street_array,1);
tempString := '';
FOR i IN 1..word_count LOOP
CONTINUE WHEN street_array[word_count-i+1] IS NULL OR street_array[word_count-i+1] = '';
tempString := COALESCE(street_array[word_count-i+1],'') || tempString;
stmt := ' SELECT'
|| ' 1,'
|| ' name,'
|| ' levenshtein_ignore_case(' || quote_literal(tempString) || ',name) as rating,'
|| ' length(name) as len'
|| ' FROM place'
|| ' WHERE ' || CASE WHEN stateAbbrev IS NOT NULL THEN 'statefp = ' || quote_literal(lstate) || ' AND ' ELSE '' END
|| ' soundex(' || quote_literal(tempString) || ') = soundex(name)'
|| ' AND levenshtein_ignore_case(' || quote_literal(tempString) || ',name) <= 2 '
|| ' UNION ALL SELECT'
|| ' 2,'
|| ' name,'
|| ' levenshtein_ignore_case(' || quote_literal(tempString) || ',name) as rating,'
|| ' length(name) as len'
|| ' FROM cousub'
|| ' WHERE ' || CASE WHEN stateAbbrev IS NOT NULL THEN 'statefp = ' || quote_literal(lstate) || ' AND ' ELSE '' END
|| ' soundex(' || quote_literal(tempString) || ') = soundex(name)'
|| ' AND levenshtein_ignore_case(' || quote_literal(tempString) || ',name) <= 2 '
|| ' ORDER BY '
|| ' 3 ASC, 1 ASC, 4 DESC'
|| ' LIMIT 1;'
;
EXECUTE stmt INTO rec;
IF rec.rating >= best THEN
location := tempString;
best := rec.rating;
END IF;
tempString := ' ' || tempString;
END LOOP;
location := replace(location,' ',ws || '+');
location := substring(fullStreet,'(?i)' || location || '$');
RETURN location;
END;
$_$ LANGUAGE plpgsql STABLE COST 100;
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