def iter_query_conditions(self, geom_type):
'''
Yields tags, columns and conditions for the current scale.
:param geom_type: one of ``'point'``, ``'line'`` or ``'polygon'``
:yields: ``[tags,]``, ``[columns,]``,
``[sqlalchemy binary expressions,]``
'''
db_class = GEOM_TYPES[geom_type]
# only one condition so it can be combined with others to get better
# performance
simple_conds = collections.defaultdict(list)
# multiple contitions
complex_conds = []
# columns which need to be fetched from database
columns = collections.defaultdict(set)
for style in self.stylesheet.iter_styles(self.mapobj.scale, geom_type):
if len(style.tag_value) == 1:
tag, value = style.tag_value.iteritems().next()
simple_conds[tag].append(value)
column_key = tag
else:
complex_conds.append(style.tag_value)
column_key = utils.dict2key(style.tag_value)
#: search for additional columns which need to be fetched from
#: from database
for attr in COLUMN_ATTRS:
if style.get(attr) in db_class.__dict__:
columns[column_key].add(style.get(attr))
for tag, names in simple_conds.iteritems():
yield [tag], columns[tag], [getattr(db_class, tag).in_(names)]
for conds in complex_conds:
tags = []
query_conds = []
for key, value in conds.iteritems():
tags.append(key)
query_conds.append(getattr(db_class, key)==value)
yield tags, columns[utils.dict2key(conds)], query_conds
def update(self, style):
'''
Adds style or overwrites existing style with new attributes.
:param style: :class:`mapython.style.Style` object
'''
#: overwrite if style is already set for this level
existing = self.get(self.zoomlevels[style.level][0], style.geom_type,
style.tag_value)
if existing is not None:
existing.attrs.update(style.attrs)
else: # style not set for this level
self.styles[style.level][style.geom_type] \
[utils.dict2key(style.tag_value)] = style
def get(self, scale, geom_type, tag_value, default=None):
'''
Returns style or default for given settings.
:param scale: metres per pixel or point
:param geom_type: one of ``'point'``, ``'line'`` or ``'polygon'``
:param tag_value: dict specifying the tags and values of the style,
e.g. ``{'highway':'motorway', ...}``
:param default: default value if no style is found
:returns: :class:`mapython.style.Style` or default
'''
level = self.get_level(scale)
try:
return self.styles[level][geom_type][utils.dict2key(tag_value)]
except KeyError:
return default
