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.mysql.query import GEOM_FROM_TEXT
# Quotename & geographic quotename, respectively.
qn = connection.ops.quote_name
class MySQLGeoField(Field):
"""
The backend-specific geographic field for MySQL.
"""
def _geom_index(self, style, db_table):
"""
Creates a spatial index for the geometry column. If MyISAM tables are
used an R-Tree index is created, otherwise a B-Tree index is created.
Thus, for best spatial performance, you should use MyISAM tables
(which do not support transactions). For more information, see Ch.
16.6.1 of the MySQL 5.0 documentation.
"""
# Getting the index name.
idx_name = '%s_%s_id' % (db_table, self.column)
sql = style.SQL_KEYWORD('CREATE SPATIAL INDEX ') + \
style.SQL_TABLE(qn(idx_name)) + \
style.SQL_KEYWORD(' ON ') + \
style.SQL_TABLE(qn(db_table)) + '(' + \
style.SQL_FIELD(qn(self.column)) + ');'
return sql
def _post_create_sql(self, style, db_table):
"""
Returns SQL that will be executed after the model has been
created.
"""
# Getting the geometric index for this Geometry column.
if self._index:
return (self._geom_index(style, db_table),)
else:
return ()
def db_type(self):
"The OpenGIS name is returned for the MySQL database column type."
return self._geom
def get_placeholder(self, value):
"""
The placeholder here has to include MySQL's WKT constructor. Because
MySQL does not support spatial transformations, there is no need to
modify the placeholder based on the contents of the given value.
"""
return '%s(%%s)' % GEOM_FROM_TEXT