app/django/contrib/gis/db/backend/postgis/field.py
author Sverre Rabbelier <srabbelier@gmail.com>
Sat, 06 Dec 2008 14:23:53 +0000
changeset 679 77a286ff6667
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Introduce dynamic scope_path regexps Instead of relying on scope_path's being "one slash deep", we should instead allow for either: 1. scope_paths that have a pre-defined depth 2. scope_paths that can be arbitrarily deep We achieve 1 by setting an entities scope_logic to another logic module. We then recursively call getScopeDepth until we get to the topmost entity (that is, an unscoped entity). A little different is the solution to 2, since some entities can have an arbitrarily deep scope (such as Documents), we need to have some way of signaling this to getScopePattern. A clean solution is to return None, rather than a number. If None is returned, the SCOPE_PATH_ARG_PATTERN is returned as regexp instead, which will match an arbitrarily deeply nested scope. The solution for 2 requires that we return None somewhere in the scope_logic chain, the most straight forward method to do so is to override getScopeDepth anywhere such a scope is needed and make it return None. A more elegant solution however, is to set the scope_logic to that module in all entities that require it. Patch by: Sverre Rabbelier

from django.db import connection
from django.db.models.fields import Field # Django base Field class
from django.contrib.gis.db.backend.util import gqn
from django.contrib.gis.db.backend.postgis.query import TRANSFORM

# Quotename & geographic quotename, respectively
qn = connection.ops.quote_name

class PostGISField(Field):
    """
    The backend-specific geographic field for PostGIS.
    """

    def _add_geom(self, style, db_table):
        """
        Constructs the addition of the geometry to the table using the
        AddGeometryColumn(...) PostGIS (and OGC standard) stored procedure.

        Takes the style object (provides syntax highlighting) and the
        database table as parameters.
        """
        sql = style.SQL_KEYWORD('SELECT ') + \
              style.SQL_TABLE('AddGeometryColumn') + '(' + \
              style.SQL_TABLE(gqn(db_table)) + ', ' + \
              style.SQL_FIELD(gqn(self.column)) + ', ' + \
              style.SQL_FIELD(str(self._srid)) + ', ' + \
              style.SQL_COLTYPE(gqn(self._geom)) + ', ' + \
              style.SQL_KEYWORD(str(self._dim)) + ');'

        if not self.null:
            # Add a NOT NULL constraint to the field
            sql += '\n' + \
                   style.SQL_KEYWORD('ALTER TABLE ') + \
                   style.SQL_TABLE(qn(db_table)) + \
                   style.SQL_KEYWORD(' ALTER ') + \
                   style.SQL_FIELD(qn(self.column)) + \
                   style.SQL_KEYWORD(' SET NOT NULL') + ';'
        return sql
    
    def _geom_index(self, style, db_table,
                    index_type='GIST', index_opts='GIST_GEOMETRY_OPS'):
        "Creates a GiST index for this geometry field."
        sql = style.SQL_KEYWORD('CREATE INDEX ') + \
              style.SQL_TABLE(qn('%s_%s_id' % (db_table, self.column))) + \
              style.SQL_KEYWORD(' ON ') + \
              style.SQL_TABLE(qn(db_table)) + \
              style.SQL_KEYWORD(' USING ') + \
              style.SQL_COLTYPE(index_type) + ' ( ' + \
              style.SQL_FIELD(qn(self.column)) + ' ' + \
              style.SQL_KEYWORD(index_opts) + ' );'
        return sql

    def post_create_sql(self, style, db_table):
        """
        Returns SQL that will be executed after the model has been
        created. Geometry columns must be added after creation with the
        PostGIS AddGeometryColumn() function.
        """

        # Getting the AddGeometryColumn() SQL necessary to create a PostGIS
        # geometry field.
        post_sql = self._add_geom(style, db_table)

        # If the user wants to index this data, then get the indexing SQL as well.
        if self._index:
            return (post_sql, self._geom_index(style, db_table))
        else:
            return (post_sql,)

    def _post_delete_sql(self, style, db_table):
        "Drops the geometry column."
        sql = style.SQL_KEYWORD('SELECT ') + \
            style.SQL_KEYWORD('DropGeometryColumn') + '(' + \
            style.SQL_TABLE(gqn(db_table)) + ', ' + \
            style.SQL_FIELD(gqn(self.column)) +  ');'
        return sql

    def db_type(self):
        """
        PostGIS geometry columns are added by stored procedures, should be
        None.
        """
        return None

    def get_placeholder(self, value):
        """
        Provides a proper substitution value for Geometries that are not in the
        SRID of the field.  Specifically, this routine will substitute in the
        ST_Transform() function call.
        """
        if value is None or value.srid == self._srid:
            return '%s'
        else:
            # Adding Transform() to the SQL placeholder.
            return '%s(%%s, %s)' % (TRANSFORM, self._srid)