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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.util import gqn |
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4 from django.contrib.gis.db.backend.postgis.query import TRANSFORM |
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5 |
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6 # Quotename & geographic quotename, respectively |
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7 qn = connection.ops.quote_name |
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8 |
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9 class PostGISField(Field): |
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10 """ |
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11 The backend-specific geographic field for PostGIS. |
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12 """ |
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13 |
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14 def _add_geom(self, style, db_table): |
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15 """ |
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16 Constructs the addition of the geometry to the table using the |
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17 AddGeometryColumn(...) PostGIS (and OGC standard) stored procedure. |
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18 |
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19 Takes the style object (provides syntax highlighting) and the |
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20 database table as parameters. |
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21 """ |
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22 sql = style.SQL_KEYWORD('SELECT ') + \ |
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23 style.SQL_TABLE('AddGeometryColumn') + '(' + \ |
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24 style.SQL_TABLE(gqn(db_table)) + ', ' + \ |
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25 style.SQL_FIELD(gqn(self.column)) + ', ' + \ |
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26 style.SQL_FIELD(str(self._srid)) + ', ' + \ |
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27 style.SQL_COLTYPE(gqn(self._geom)) + ', ' + \ |
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28 style.SQL_KEYWORD(str(self._dim)) + ');' |
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29 |
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30 if not self.null: |
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31 # Add a NOT NULL constraint to the field |
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32 sql += '\n' + \ |
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33 style.SQL_KEYWORD('ALTER TABLE ') + \ |
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34 style.SQL_TABLE(qn(db_table)) + \ |
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35 style.SQL_KEYWORD(' ALTER ') + \ |
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36 style.SQL_FIELD(qn(self.column)) + \ |
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37 style.SQL_KEYWORD(' SET NOT NULL') + ';' |
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38 return sql |
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39 |
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40 def _geom_index(self, style, db_table, |
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41 index_type='GIST', index_opts='GIST_GEOMETRY_OPS'): |
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42 "Creates a GiST index for this geometry field." |
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43 sql = style.SQL_KEYWORD('CREATE INDEX ') + \ |
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44 style.SQL_TABLE(qn('%s_%s_id' % (db_table, self.column))) + \ |
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45 style.SQL_KEYWORD(' ON ') + \ |
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46 style.SQL_TABLE(qn(db_table)) + \ |
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47 style.SQL_KEYWORD(' USING ') + \ |
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48 style.SQL_COLTYPE(index_type) + ' ( ' + \ |
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49 style.SQL_FIELD(qn(self.column)) + ' ' + \ |
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50 style.SQL_KEYWORD(index_opts) + ' );' |
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51 return sql |
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52 |
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53 def post_create_sql(self, style, db_table): |
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54 """ |
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55 Returns SQL that will be executed after the model has been |
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56 created. Geometry columns must be added after creation with the |
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57 PostGIS AddGeometryColumn() function. |
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58 """ |
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59 |
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60 # Getting the AddGeometryColumn() SQL necessary to create a PostGIS |
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61 # geometry field. |
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62 post_sql = self._add_geom(style, db_table) |
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63 |
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64 # If the user wants to index this data, then get the indexing SQL as well. |
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65 if self._index: |
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66 return (post_sql, self._geom_index(style, db_table)) |
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67 else: |
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68 return (post_sql,) |
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69 |
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70 def _post_delete_sql(self, style, db_table): |
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71 "Drops the geometry column." |
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72 sql = style.SQL_KEYWORD('SELECT ') + \ |
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73 style.SQL_KEYWORD('DropGeometryColumn') + '(' + \ |
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74 style.SQL_TABLE(gqn(db_table)) + ', ' + \ |
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75 style.SQL_FIELD(gqn(self.column)) + ');' |
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76 return sql |
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77 |
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78 def db_type(self): |
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79 """ |
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80 PostGIS geometry columns are added by stored procedures, should be |
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81 None. |
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82 """ |
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83 return None |
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84 |
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85 def get_placeholder(self, value): |
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86 """ |
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87 Provides a proper substitution value for Geometries that are not in the |
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88 SRID of the field. Specifically, this routine will substitute in the |
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89 ST_Transform() function call. |
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90 """ |
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91 if value is None or value.srid == self._srid: |
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92 return '%s' |
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93 else: |
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94 # Adding Transform() to the SQL placeholder. |
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95 return '%s(%%s, %s)' % (TRANSFORM, self._srid) |