[Maposmatic-dev] [PATCH ocitysmap] Improve the map_areas table name parametrization

[Maxime Petazzoni]

Previously, the map_areas table name was taken from the ocitysmap.conf
configuration file (from the wrong section when compared to the provided
configuration file example...), falling back to a sensible default. This
didn't really help make things easier to run several ocitysmap rendering
processes in parallel, as they would need separate, pre-existing
configuration files.

A table name prefix can now be provided to the OCitySMap initalization
function instead of through the configuration file. The map_areas table
name is then constructed from this prefix with '<prefix>map_areas'.
Example prefixes are: 'RENDERERNAME_PID_', 'myjob_', 'another_'.

The temporary table is also now automatically cleaned up after
processing (failing or not).
---
 ocitysmap-render          |    5 ++-
 ocitysmap.conf            |    1 -
 ocitysmap/street_index.py |   70 ++++++++++++++++++++++++++++----------------
 3 files changed, 47 insertions(+), 29 deletions(-)

diff --git a/ocitysmap-render b/ocitysmap-render
index d0800af..881e0e9 100755
--- a/ocitysmap-render
+++ b/ocitysmap-render
@@ -134,8 +134,9 @@ def main():
             return 1
 
     try:
-        renderer = OCitySMap(options.config_file, city_name, boundingbox,
-                             osmid, options.language)
+        prefix = 'ocitysmap_render_%d' % os.getpid()
+        renderer = OCitySMap(options.config_file, prefix, city_name,
+                             boundingbox, osmid, options.language)
     except BaseOCitySMapError, e:
         sys.stderr.write('ERROR: %s\n' % e)
         return 1
diff --git a/ocitysmap.conf b/ocitysmap.conf
index c9ed096..0d6bb04 100644
--- a/ocitysmap.conf
+++ b/ocitysmap.conf
@@ -27,7 +27,6 @@ dbname=maposmatic
 
 [mapnik]
 map=/path/to/mapnik-osm/osm.xml
-map_areas_table_name=some_name_for_the_map_areas_table
 
 [ocitysmap]
 copyright_logo=/path/to/ocitysmap/Openstreetmap_logo.png
diff --git a/ocitysmap/street_index.py b/ocitysmap/street_index.py
index 0b7a8c9..034e245 100644
--- a/ocitysmap/street_index.py
+++ b/ocitysmap/street_index.py
@@ -235,12 +235,13 @@ class IndexPageGenerator:
                 x += colwidth
 
 class OCitySMap:
-    def __init__(self, config_file=None, city_name=None, boundingbox=None,
-                 osmid=None, language=None):
+    def __init__(self, config_file=None, map_areas_prefix=None,
+                 city_name=None, boundingbox=None, osmid=None, language=None):
         """Creates a new OCitySMap renderer instance for the given city.
 
         Args:
-            config_file: location of the config file
+            config_file (string): location of the config file
+            map_areas_prefix (string): map_areas table name prefix
             city_name (string): The name of the city we're created the map of.
             boundingbox (BoundingBox): An optional BoundingBox object defining
                 the city's bounding box. If not given, OCitySMap will try to
@@ -279,10 +280,9 @@ class OCitySMap:
         self.i18n = i18n.install_translation(language, locale_path)
         LOG.info('Language: ' + self.i18n.language_code())
 
-        self._map_areas_table_name = "map_areas"
-        if self.parser.has_option('ocitysmap', 'map_areas_table_name'):
-            self._map_areas_table_name = self.parser.get('ocitysmap',
-                                                         
'map_areas_table_name')
+        # Create the map_areas table name string using the provided prefix
+        map_areas_prefix = map_areas_prefix or ''
+        self._map_areas_table_name = '%smap_areas' % map_areas_prefix
 
         self.SELECTED_AMENITIES = [
             (_(u"Places of worship"), "place_of_worship", _(u"Place of 
worship")),
@@ -326,24 +326,29 @@ class OCitySMap:
 
         self.griddesc = grid.GridDescriptor(self.boundingbox, db)
 
-        self._gen_map_areas(db)
-
-        if self.osmid:
-            self.streets = self.get_streets_by_osmid(db, self.osmid)
-            self.amenities = self.get_amenities_by_osmid(db, self.osmid)
-        elif self.city_name:
-            self.streets = self.get_streets_by_name(db, self.city_name)
-            self.amenities = self.get_amenities_by_name(db, self.city_name)
-        else:
-            self.streets = self.get_streets_by_name(db, None)
-            self.amenities = self.get_amenities_by_name(db, None)
+        try:
+            self._gen_map_areas(db)
+
+            if self.osmid:
+                self.streets = self.get_streets_by_osmid(db, self.osmid)
+                self.amenities = self.get_amenities_by_osmid(db, self.osmid)
+            elif self.city_name:
+                self.streets = self.get_streets_by_name(db, self.city_name)
+                self.amenities = self.get_amenities_by_name(db, self.city_name)
+            else:
+                self.streets = self.get_streets_by_name(db, None)
+                self.amenities = self.get_amenities_by_name(db, None)
 
-        if self.city_name:
-            self.contour = self.get_city_contour_by_name(db, self.city_name)
-        elif self.osmid:
-            self.contour = self.get_city_contour_by_osmid(db, self.osmid)
-        else:
-            self.contour = None
+            if self.city_name:
+                self.contour = self.get_city_contour_by_name(db, 
self.city_name)
+            elif self.osmid:
+                self.contour = self.get_city_contour_by_osmid(db, self.osmid)
+            else:
+                self.contour = None
+        finally:
+            LOG.debug('Restoring database state...')
+            db.rollback()
+            self._del_map_areas(db)
 
         LOG.info('City bounding box is %s.' % str(self.boundingbox))
 
@@ -493,9 +498,13 @@ class OCitySMap:
         LOG.debug('Call gen_map_areas table: %s...'
                   % self._map_areas_table_name)
 
-        LOG.debug('drop...')
+        # Make sure our map_areas table does not exist already. We don't call
+        # _del_map_areas here because we want this to be part of the local
+        # DB transaction.
+        LOG.debug('drop %s...' % self._map_areas_table_name)
         cursor.execute("drop table if exists %s" % self._map_areas_table_name)
-        LOG.debug('create table...')
+
+        LOG.debug('create table %s...' % self._map_areas_table_name)
         cursor.execute("create table %s (x integer, y integer)"
                        % self._map_areas_table_name)
         LOG.debug('addgeometrycolumn...')
@@ -523,6 +532,15 @@ class OCitySMap:
         LOG.debug('Done with gen_map_areas for %s.'
                   % self._map_areas_table_name)
 
+    def _del_map_areas(self, db):
+        """Destroys the map_areas table used by this OCitySMap instance
+        (parametrized by its prefix)."""
+
+        cursor = db.cursor()
+        LOG.debug('drop %s...' % self._map_areas_table_name)
+        cursor.execute("drop table if exists %s" % self._map_areas_table_name)
+        db.commit()
+
     # Given a list of street and their corresponding squares, do some
     # cleanup and pass it through the internationalization layer to
     # get proper sorting, filtering of common prefixes, etc. Returns a
-- 
1.6.3.3.277.g88938c