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