1 from django.db import connection |
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2 from django.db.models.fields import Field # Django base Field class |
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3 from django.contrib.gis.db.backend.mysql.query import GEOM_FROM_TEXT |
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4 |
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5 # Quotename & geographic quotename, respectively. |
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6 qn = connection.ops.quote_name |
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7 |
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8 class MySQLGeoField(Field): |
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9 """ |
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10 The backend-specific geographic field for MySQL. |
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11 """ |
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12 |
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13 def _geom_index(self, style, db_table): |
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14 """ |
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15 Creates a spatial index for the geometry column. If MyISAM tables are |
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16 used an R-Tree index is created, otherwise a B-Tree index is created. |
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17 Thus, for best spatial performance, you should use MyISAM tables |
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18 (which do not support transactions). For more information, see Ch. |
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19 16.6.1 of the MySQL 5.0 documentation. |
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20 """ |
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21 |
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22 # Getting the index name. |
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23 idx_name = '%s_%s_id' % (db_table, self.column) |
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24 |
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25 sql = (style.SQL_KEYWORD('CREATE SPATIAL INDEX ') + |
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26 style.SQL_TABLE(qn(idx_name)) + |
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27 style.SQL_KEYWORD(' ON ') + |
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28 style.SQL_TABLE(qn(db_table)) + '(' + |
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29 style.SQL_FIELD(qn(self.column)) + ');') |
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30 return sql |
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31 |
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32 def post_create_sql(self, style, db_table): |
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33 """ |
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34 Returns SQL that will be executed after the model has been |
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35 created. |
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36 """ |
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37 # Getting the geometric index for this Geometry column. |
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38 if self.spatial_index: |
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39 return (self._geom_index(style, db_table),) |
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40 else: |
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41 return () |
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42 |
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43 def db_type(self): |
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44 "The OpenGIS name is returned for the MySQL database column type." |
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45 return self.geom_type |
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46 |
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47 def get_placeholder(self, value): |
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48 """ |
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49 The placeholder here has to include MySQL's WKT constructor. Because |
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50 MySQL does not support spatial transformations, there is no need to |
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51 modify the placeholder based on the contents of the given value. |
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52 """ |
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53 return '%s(%%s)' % GEOM_FROM_TEXT |
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