/[thuban]/branches/WIP-pyshapelib-bramz/Thuban/Model/transientdb.py
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revision 1043 by bh, Mon May 26 19:27:15 2003 UTC revision 1364 by bh, Thu Jul 3 13:09:43 2003 UTC
# Line 379  class TransientJoinedTable(TitledObject, Line 379  class TransientJoinedTable(TitledObject,
379          that the value of the left_field column the the left table is          that the value of the left_field column the the left table is
380          equal to the value of the right_field in the right_table.          equal to the value of the right_field in the right_table.
381    
382          The joined table contains all columns of the input tables with          The joined table contains all columns of the input tables,
383          one exception: Any column in the right_table with the same name          however, the column names of the right table may be changed
384          as one of the columns in the left_table will be omitted. This is          slightly to make them unique in the joined table. This is
385          somewhat of an implementation detail, but is done so that the          currently done by appending a sufficient number of underscores
386          column names of the joined table can be the same as the column          ('_').
         names of the input tables without having to create prefixes.  
387          """          """
388          TransientTableBase.__init__(self, transient_db)          TransientTableBase.__init__(self, transient_db)
389          self.dependencies = (left_table, right_table)          self.dependencies = (left_table, right_table)
# Line 410  class TransientJoinedTable(TitledObject, Line 409  class TransientJoinedTable(TitledObject,
409    
410          self.right_table.ensure_index(self.right_field)          self.right_table.ensure_index(self.right_field)
411    
412            # determine the internal column names to join on before
413            # coalescing the column information because if the external
414            # column names are the same they will be mapped to the same
415            # internal name afterwards.
416            internal_left_col = self.left_table.orig_to_internal[self.left_field]
417            internal_right_col =self.right_table.orig_to_internal[self.right_field]
418    
419          # Coalesce the column information          # Coalesce the column information
420          visited = {}          visited = {}
421          columns = []          columns = []
422          for col in self.left_table.columns + self.right_table.columns:          newcolumns = []
423              if col.name in visited:          for table in (self.left_table, self.right_table):
424                  # We can't allow multiple columns with the same original              for col in table.Columns():
425                  # name, so omit this one. FIXME: There should be a                  colname = col.name
426                  # better solution.                  # We can't allow multiple columns with the same
427                  continue                  # original name, so append '_' to this one until
428              columns.append(col)                  # it is unique.
429          TransientTableBase.create(self, columns)                  # FIXME: There should be a better solution.
430                    while colname in visited:
431                        colname = colname + '_'
432                    columns.append((table.tablename, col))
433                    newcol = ColumnReference(colname, col.type,
434                                                "Col%03d" % (len(newcolumns)+1))
435                    newcolumns.append(newcol)
436                    visited[colname] = 1
437            TransientTableBase.create(self, newcolumns)
438    
439          # Copy the joined data to the table.          # Copy the joined data to the table.
440          internal_names = [col.internal_name for col in self.columns]          newinternal_names = [col.internal_name for col in self.columns]
441            internal_references = ["%s.%s" % (table, col.internal_name)
442                                                        for table, col in columns]
443          if self.outer_join:          if self.outer_join:
444              join_operator = 'LEFT OUTER JOIN'              join_operator = 'LEFT OUTER JOIN'
445          else:          else:
446              join_operator = 'JOIN'              join_operator = 'JOIN'
447          stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"          stmt = ("INSERT INTO %s (id, %s) SELECT %s.id, %s FROM %s"
448                  " %s %s ON %s = %s;"                  " %s %s ON %s.%s = %s.%s;"
449                  % (self.tablename,                  % (self.tablename,
450                     ", ".join(internal_names),                     ", ".join(newinternal_names),
451                     self.left_table.tablename,                     self.left_table.tablename,
452                     ", ".join(internal_names),                     ", ".join(internal_references),
453                     self.left_table.tablename,                     self.left_table.tablename,
454                     join_operator,                     join_operator,
455                     self.right_table.tablename,                     self.right_table.tablename,
456                     self.orig_to_internal[self.left_field],                     self.left_table.tablename,
457                     self.orig_to_internal[self.right_field]))                     internal_left_col,
458                       self.right_table.tablename,
459                       internal_right_col))
460          self.db.execute(stmt)          self.db.execute(stmt)
461    
462      def Dependencies(self):      def Dependencies(self):
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