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1 """ |
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2 This module contains the spatial lookup types, and the `get_geo_where_clause` |
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3 routine for MySQL. |
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4 |
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5 Please note that MySQL only supports bounding box queries, also |
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6 known as MBRs (Minimum Bounding Rectangles). Moreover, spatial |
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7 indices may only be used on MyISAM tables -- if you need |
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8 transactions, take a look at PostGIS. |
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9 """ |
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10 from django.db import connection |
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11 qn = connection.ops.quote_name |
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12 |
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13 # To ease implementation, WKT is passed to/from MySQL. |
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14 GEOM_FROM_TEXT = 'GeomFromText' |
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15 GEOM_FROM_WKB = 'GeomFromWKB' |
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16 GEOM_SELECT = 'AsText(%s)' |
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17 |
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18 # WARNING: MySQL is NOT compliant w/the OpenGIS specification and |
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19 # _every_ one of these lookup types is on the _bounding box_ only. |
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20 MYSQL_GIS_FUNCTIONS = { |
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21 'bbcontains' : 'MBRContains', # For consistency w/PostGIS API |
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22 'bboverlaps' : 'MBROverlaps', # .. .. |
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23 'contained' : 'MBRWithin', # .. .. |
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24 'contains' : 'MBRContains', |
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25 'disjoint' : 'MBRDisjoint', |
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26 'equals' : 'MBREqual', |
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27 'exact' : 'MBREqual', |
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28 'intersects' : 'MBRIntersects', |
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29 'overlaps' : 'MBROverlaps', |
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30 'same_as' : 'MBREqual', |
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31 'touches' : 'MBRTouches', |
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32 'within' : 'MBRWithin', |
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33 } |
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34 |
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35 # This lookup type does not require a mapping. |
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36 MISC_TERMS = ['isnull'] |
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37 |
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38 # Assacceptable lookup types for Oracle spatial. |
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39 MYSQL_GIS_TERMS = MYSQL_GIS_FUNCTIONS.keys() |
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40 MYSQL_GIS_TERMS += MISC_TERMS |
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41 MYSQL_GIS_TERMS = dict((term, None) for term in MYSQL_GIS_TERMS) # Making dictionary |
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42 |
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43 def get_geo_where_clause(table_alias, name, lookup_type, geo_annot): |
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44 "Returns the SQL WHERE clause for use in MySQL spatial SQL construction." |
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45 # Getting the quoted field as `geo_col`. |
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46 geo_col = '%s.%s' % (qn(table_alias), qn(name)) |
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47 |
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48 # See if a MySQL Geometry function matches the lookup type next |
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49 lookup_info = MYSQL_GIS_FUNCTIONS.get(lookup_type, False) |
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50 if lookup_info: |
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51 return "%s(%s, %%s)" % (lookup_info, geo_col) |
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52 |
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53 # Handling 'isnull' lookup type |
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54 # TODO: Is this needed because MySQL cannot handle NULL |
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55 # geometries in its spatial indices. |
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56 if lookup_type == 'isnull': |
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57 return "%s IS %sNULL" % (geo_col, (not geo_annot.value and 'NOT ' or '')) |
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58 |
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59 raise TypeError("Got invalid lookup_type: %s" % repr(lookup_type)) |