nominatim/tools/postcodes.py

   1 """
   2 Functions for importing, updating and otherwise maintaining the table
   3 of artificial postcode centroids.
   4 """
   5 import csv
   6 import gzip
   7 import logging
   8 from math import isfinite
   9
  10 from psycopg2.extras import execute_values
  11
  12 from nominatim.db.connection import connect
  13
  14 LOG = logging.getLogger()
  15
  16 def _to_float(num, max_value):
  17     """ Convert the number in string into a float. The number is expected
  18         to be in the range of [-max_value, max_value]. Otherwise rises a
  19         ValueError.
  20     """
  21     num = float(num)
  22     if not isfinite(num) or num <= -max_value or num >= max_value:
  23         raise ValueError()
  24
  25     return num
  26
  27 class _CountryPostcodesCollector:
  28     """ Collector for postcodes of a single country.
  29     """
  30
  31     def __init__(self, country):
  32         self.country = country
  33         self.collected = dict()
  34
  35
  36     def add(self, postcode, x, y):
  37         """ Add the given postcode to the collection cache. If the postcode
  38             already existed, it is overwritten with the new centroid.
  39         """
  40         self.collected[postcode] = (x, y)
  41
  42
  43     def commit(self, conn, analyzer, project_dir):
  44         """ Update postcodes for the country from the postcodes selected so far
  45             as well as any externally supplied postcodes.
  46         """
  47         self._update_from_external(analyzer, project_dir)
  48         to_add, to_delete, to_update = self._compute_changes(conn)
  49
  50         LOG.info("Processing country '%s' (%s added, %s deleted, %s updated).",
  51                  self.country, len(to_add), len(to_delete), len(to_update))
  52
  53         with conn.cursor() as cur:
  54             if to_add:
  55                 execute_values(cur,
  56                                """INSERT INTO location_postcode
  57                                       (place_id, indexed_status, country_code,
  58                                        postcode, geometry) VALUES %s""",
  59                                to_add,
  60                                template="""(nextval('seq_place'), 1, '{}',
  61                                            %s, 'SRID=4326;POINT(%s %s)')
  62                                         """.format(self.country))
  63             if to_delete:
  64                 cur.execute("""DELETE FROM location_postcode
  65                                WHERE country_code = %s and postcode = any(%s)
  66                             """, (self.country, to_delete))
  67             if to_update:
  68                 execute_values(cur,
  69                                """UPDATE location_postcode
  70                                   SET indexed_status = 2,
  71                                       geometry = ST_SetSRID(ST_Point(v.x, v.y), 4326)
  72                                   FROM (VALUES %s) AS v (pc, x, y)
  73                                   WHERE country_code = '{}' and postcode = pc
  74                                """.format(self.country),
  75                                to_update)
  76
  77
  78     def _compute_changes(self, conn):
  79         """ Compute which postcodes from the collected postcodes have to be
  80             added or modified and which from the location_postcode table
  81             have to be deleted.
  82         """
  83         to_update = []
  84         to_delete = []
  85         with conn.cursor() as cur:
  86             cur.execute("""SELECT postcode, ST_X(geometry), ST_Y(geometry)
  87                            FROM location_postcode
  88                            WHERE country_code = %s""",
  89                         (self.country, ))
  90             for postcode, x, y in cur:
  91                 newx, newy = self.collected.pop(postcode, (None, None))
  92                 if newx is not None:
  93                     dist = (x - newx)**2 + (y - newy)**2
  94                     if dist > 0.0000001:
  95                         to_update.append((postcode, newx, newy))
  96                 else:
  97                     to_delete.append(postcode)
  98
  99         to_add = [(k, v[0], v[1]) for k, v in self.collected.items()]
 100         self.collected = []
 101
 102         return to_add, to_delete, to_update
 103
 104
 105     def _update_from_external(self, analyzer, project_dir):
 106         """ Look for an external postcode file for the active country in
 107             the project directory and add missing postcodes when found.
 108         """
 109         csvfile = self._open_external(project_dir)
 110         if csvfile is None:
 111             return
 112
 113         try:
 114             reader = csv.DictReader(csvfile)
 115             for row in reader:
 116                 if 'postcode' not in row or 'lat' not in row or 'lon' not in row:
 117                     LOG.warning("Bad format for external postcode file for country '%s'."
 118                                 " Ignored.", self.country)
 119                     return
 120                 postcode = analyzer.normalize_postcode(row['postcode'])
 121                 if postcode not in self.collected:
 122                     try:
 123                         self.collected[postcode] = (_to_float(row['lon'], 180),
 124                                                     _to_float(row['lat'], 90))
 125                     except ValueError:
 126                         LOG.warning("Bad coordinates %s, %s in %s country postcode file.",
 127                                     row['lat'], row['lon'], self.country)
 128
 129         finally:
 130             csvfile.close()
 131
 132
 133     def _open_external(self, project_dir):
 134         fname = project_dir / '{}_postcodes.csv'.format(self.country)
 135
 136         if fname.is_file():
 137             LOG.info("Using external postcode file '%s'.", fname)
 138             return open(fname, 'r')
 139
 140         fname = project_dir / '{}_postcodes.csv.gz'.format(self.country)
 141
 142         if fname.is_file():
 143             LOG.info("Using external postcode file '%s'.", fname)
 144             return gzip.open(fname, 'rt')
 145
 146         return None
 147
 148
 149 def update_postcodes(dsn, project_dir, tokenizer):
 150     """ Update the table of artificial postcodes.
 151
 152         Computes artificial postcode centroids from the placex table,
 153         potentially enhances it with external data and then updates the
 154         postcodes in the table 'location_postcode'.
 155     """
 156     with tokenizer.name_analyzer() as analyzer:
 157         with connect(dsn) as conn:
 158             # First get the list of countries that currently have postcodes.
 159             # (Doing this before starting to insert, so it is fast on import.)
 160             with conn.cursor() as cur:
 161                 cur.execute("SELECT DISTINCT country_code FROM location_postcode")
 162                 todo_countries = set((row[0] for row in cur))
 163
 164             # Recompute the list of valid postcodes from placex.
 165             with conn.cursor(name="placex_postcodes") as cur:
 166                 cur.execute("""
 167                 SELECT cc as country_code, pc, ST_X(centroid), ST_Y(centroid)
 168                 FROM (
 169                     SELECT
 170                         COALESCE(plx.country_code, get_country_code(ST_Centroid(pl.geometry))) as cc,
 171                         token_normalized_postcode(pl.address->'postcode') as pc,
 172                         COALESCE(ST_Centroid(ST_Collect(plx.centroid)), ST_Centroid(ST_Collect(ST_Centroid(pl.geometry)))) as centroid
 173                     FROM place AS pl LEFT OUTER JOIN placex AS plx ON pl.osm_id = plx.osm_id AND pl.osm_type = plx.osm_type
 174                     WHERE pl.address ? 'postcode' AND pl.geometry IS NOT null
 175                     GROUP BY cc, pc
 176                 ) xx
 177                 WHERE pc IS NOT null AND cc IS NOT null
 178                 ORDER BY country_code, pc""")
 179
 180                 collector = None
 181
 182                 for country, postcode, x, y in cur:
 183                     if collector is None or country != collector.country:
 184                         if collector is not None:
 185                             collector.commit(conn, analyzer, project_dir)
 186                         collector = _CountryPostcodesCollector(country)
 187                         todo_countries.discard(country)
 188                     collector.add(postcode, x, y)
 189
 190                 if collector is not None:
 191                     collector.commit(conn, analyzer, project_dir)
 192
 193             # Now handle any countries that are only in the postcode table.
 194             for country in todo_countries:
 195                 _CountryPostcodesCollector(country).commit(conn, analyzer, project_dir)
 196
 197             conn.commit()
 198
 199         analyzer.update_postcodes_from_db()
 200
 201 def can_compute(dsn):
 202     """
 203         Check that the place table exists so that
 204         postcodes can be computed.
 205     """
 206     with connect(dsn) as conn:
 207         return conn.table_exists('place')