from itertools import izip from django.db.models.query import sql from django.db.models.fields import FieldDoesNotExist from django.db.models.fields.related import ForeignKey from django.contrib.gis.db.backend import SpatialBackend from django.contrib.gis.db.models.fields import GeometryField from django.contrib.gis.db.models.sql.where import GeoWhereNode from django.contrib.gis.measure import Area, Distance # Valid GIS query types. ALL_TERMS = sql.constants.QUERY_TERMS.copy() ALL_TERMS.update(SpatialBackend.gis_terms) class GeoQuery(sql.Query): """ A single spatial SQL query. """ # Overridding the valid query terms. query_terms = ALL_TERMS #### Methods overridden from the base Query class #### def __init__(self, model, conn): super(GeoQuery, self).__init__(model, conn, where=GeoWhereNode) # The following attributes are customized for the GeoQuerySet. # The GeoWhereNode and SpatialBackend classes contain backend-specific # routines and functions. self.aggregate = False self.custom_select = {} self.transformed_srid = None self.extra_select_fields = {} def clone(self, *args, **kwargs): obj = super(GeoQuery, self).clone(*args, **kwargs) # Customized selection dictionary and transformed srid flag have # to also be added to obj. obj.aggregate = self.aggregate obj.custom_select = self.custom_select.copy() obj.transformed_srid = self.transformed_srid obj.extra_select_fields = self.extra_select_fields.copy() return obj def get_columns(self, with_aliases=False): """ Return the list of columns to use in the select statement. If no columns have been specified, returns all columns relating to fields in the model. If 'with_aliases' is true, any column names that are duplicated (without the table names) are given unique aliases. This is needed in some cases to avoid ambiguitity with nested queries. This routine is overridden from Query to handle customized selection of geometry columns. """ qn = self.quote_name_unless_alias qn2 = self.connection.ops.quote_name result = ['(%s) AS %s' % (self.get_extra_select_format(alias) % col[0], qn2(alias)) for alias, col in self.extra_select.iteritems()] aliases = set(self.extra_select.keys()) if with_aliases: col_aliases = aliases.copy() else: col_aliases = set() if self.select: # This loop customized for GeoQuery. for col, field in izip(self.select, self.select_fields): if isinstance(col, (list, tuple)): r = self.get_field_select(field, col[0]) if with_aliases and col[1] in col_aliases: c_alias = 'Col%d' % len(col_aliases) result.append('%s AS %s' % (r, c_alias)) aliases.add(c_alias) col_aliases.add(c_alias) else: result.append(r) aliases.add(r) col_aliases.add(col[1]) else: result.append(col.as_sql(quote_func=qn)) if hasattr(col, 'alias'): aliases.add(col.alias) col_aliases.add(col.alias) elif self.default_cols: cols, new_aliases = self.get_default_columns(with_aliases, col_aliases) result.extend(cols) aliases.update(new_aliases) # This loop customized for GeoQuery. if not self.aggregate: for (table, col), field in izip(self.related_select_cols, self.related_select_fields): r = self.get_field_select(field, table) if with_aliases and col in col_aliases: c_alias = 'Col%d' % len(col_aliases) result.append('%s AS %s' % (r, c_alias)) aliases.add(c_alias) col_aliases.add(c_alias) else: result.append(r) aliases.add(r) col_aliases.add(col) self._select_aliases = aliases return result def get_default_columns(self, with_aliases=False, col_aliases=None, start_alias=None, opts=None, as_pairs=False): """ Computes the default columns for selecting every field in the base model. Returns a list of strings, quoted appropriately for use in SQL directly, as well as a set of aliases used in the select statement. This routine is overridden from Query to handle customized selection of geometry columns. """ result = [] if opts is None: opts = self.model._meta if start_alias: table_alias = start_alias else: table_alias = self.tables[0] root_pk = opts.pk.column seen = {None: table_alias} aliases = set() for field, model in opts.get_fields_with_model(): try: alias = seen[model] except KeyError: alias = self.join((table_alias, model._meta.db_table, root_pk, model._meta.pk.column)) seen[model] = alias if as_pairs: result.append((alias, field.column)) continue # This part of the function is customized for GeoQuery. We # see if there was any custom selection specified in the # dictionary, and set up the selection format appropriately. field_sel = self.get_field_select(field, alias) if with_aliases and field.column in col_aliases: c_alias = 'Col%d' % len(col_aliases) result.append('%s AS %s' % (field_sel, c_alias)) col_aliases.add(c_alias) aliases.add(c_alias) else: r = field_sel result.append(r) aliases.add(r) if with_aliases: col_aliases.add(field.column) if as_pairs: return result, None return result, aliases def get_ordering(self): """ This routine is overridden to disable ordering for aggregate spatial queries. """ if not self.aggregate: return super(GeoQuery, self).get_ordering() else: return () def resolve_columns(self, row, fields=()): """ This routine is necessary so that distances and geometries returned from extra selection SQL get resolved appropriately into Python objects. """ values = [] aliases = self.extra_select.keys() # Have to set a starting row number offset that is used for # determining the correct starting row index -- needed for # doing pagination with Oracle. rn_offset = 0 if SpatialBackend.oracle: if self.high_mark is not None or self.low_mark: rn_offset = 1 index_start = rn_offset + len(aliases) # Converting any extra selection values (e.g., geometries and # distance objects added by GeoQuerySet methods). values = [self.convert_values(v, self.extra_select_fields.get(a, None)) for v, a in izip(row[rn_offset:index_start], aliases)] if SpatialBackend.oracle: # This is what happens normally in OracleQuery's `resolve_columns`. for value, field in izip(row[index_start:], fields): values.append(self.convert_values(value, field)) else: values.extend(row[index_start:]) return values def convert_values(self, value, field): """ Using the same routines that Oracle does we can convert our extra selection objects into Geometry and Distance objects. TODO: Make converted objects 'lazy' for less overhead. """ if SpatialBackend.oracle: # Running through Oracle's first. value = super(GeoQuery, self).convert_values(value, field) if isinstance(field, DistanceField): # Using the field's distance attribute, can instantiate # `Distance` with the right context. value = Distance(**{field.distance_att : value}) elif isinstance(field, AreaField): value = Area(**{field.area_att : value}) elif isinstance(field, GeomField): value = SpatialBackend.Geometry(value) return value #### Routines unique to GeoQuery #### def get_extra_select_format(self, alias): sel_fmt = '%s' if alias in self.custom_select: sel_fmt = sel_fmt % self.custom_select[alias] return sel_fmt def get_field_select(self, fld, alias=None): """ Returns the SELECT SQL string for the given field. Figures out if any custom selection SQL is needed for the column The `alias` keyword may be used to manually specify the database table where the column exists, if not in the model associated with this `GeoQuery`. """ sel_fmt = self.get_select_format(fld) if fld in self.custom_select: field_sel = sel_fmt % self.custom_select[fld] else: field_sel = sel_fmt % self._field_column(fld, alias) return field_sel def get_select_format(self, fld): """ Returns the selection format string, depending on the requirements of the spatial backend. For example, Oracle and MySQL require custom selection formats in order to retrieve geometries in OGC WKT. For all other fields a simple '%s' format string is returned. """ if SpatialBackend.select and hasattr(fld, '_geom'): # This allows operations to be done on fields in the SELECT, # overriding their values -- used by the Oracle and MySQL # spatial backends to get database values as WKT, and by the # `transform` method. sel_fmt = SpatialBackend.select # Because WKT doesn't contain spatial reference information, # the SRID is prefixed to the returned WKT to ensure that the # transformed geometries have an SRID different than that of the # field -- this is only used by `transform` for Oracle backends. if self.transformed_srid and SpatialBackend.oracle: sel_fmt = "'SRID=%d;'||%s" % (self.transformed_srid, sel_fmt) else: sel_fmt = '%s' return sel_fmt # Private API utilities, subject to change. def _check_geo_field(self, model, name_param): """ Recursive utility routine for checking the given name parameter on the given model. Initially, the name parameter is a string, of the field on the given model e.g., 'point', 'the_geom'. Related model field strings like 'address__point', may also be used. If a GeometryField exists according to the given name parameter it will be returned, otherwise returns False. """ if isinstance(name_param, basestring): # This takes into account the situation where the name is a # lookup to a related geographic field, e.g., 'address__point'. name_param = name_param.split(sql.constants.LOOKUP_SEP) name_param.reverse() # Reversing so list operates like a queue of related lookups. elif not isinstance(name_param, list): raise TypeError try: # Getting the name of the field for the model (by popping the first # name from the `name_param` list created above). fld, mod, direct, m2m = model._meta.get_field_by_name(name_param.pop()) except (FieldDoesNotExist, IndexError): return False # TODO: ManyToManyField? if isinstance(fld, GeometryField): return fld # A-OK. elif isinstance(fld, ForeignKey): # ForeignKey encountered, return the output of this utility called # on the _related_ model with the remaining name parameters. return self._check_geo_field(fld.rel.to, name_param) # Recurse to check ForeignKey relation. else: return False def _field_column(self, field, table_alias=None): """ Helper function that returns the database column for the given field. The table and column are returned (quoted) in the proper format, e.g., `"geoapp_city"."point"`. If `table_alias` is not specified, the database table associated with the model of this `GeoQuery` will be used. """ if table_alias is None: table_alias = self.model._meta.db_table return "%s.%s" % (self.quote_name_unless_alias(table_alias), self.connection.ops.quote_name(field.column)) def _geo_field(self, field_name=None): """ Returns the first Geometry field encountered; or specified via the `field_name` keyword. The `field_name` may be a string specifying the geometry field on this GeoQuery's model, or a lookup string to a geometry field via a ForeignKey relation. """ if field_name is None: # Incrementing until the first geographic field is found. for fld in self.model._meta.fields: if isinstance(fld, GeometryField): return fld return False else: # Otherwise, check by the given field name -- which may be # a lookup to a _related_ geographic field. return self._check_geo_field(self.model, field_name) ### Field Classes for `convert_values` #### class AreaField(object): def __init__(self, area_att): self.area_att = area_att class DistanceField(object): def __init__(self, distance_att): self.distance_att = distance_att # Rather than use GeometryField (which requires a SQL query # upon instantiation), use this lighter weight class. class GeomField(object): pass