python/lib/django-1.5/django/db/backends/oracle/compiler.py

   1 from django.db.models.sql import compiler
   2 # The izip_longest was renamed to zip_longest in py3
   3 try:
   4     from itertools import zip_longest
   5 except ImportError:
   6     from itertools import izip_longest as zip_longest
   7
   8
   9 class SQLCompiler(compiler.SQLCompiler):
  10     def resolve_columns(self, row, fields=()):
  11         # If this query has limit/offset information, then we expect the
  12         # first column to be an extra "_RN" column that we need to throw
  13         # away.
  14         if self.query.high_mark is not None or self.query.low_mark:
  15             rn_offset = 1
  16         else:
  17             rn_offset = 0
  18         index_start = rn_offset + len(self.query.extra_select)
  19         values = [self.query.convert_values(v, None, connection=self.connection)
  20                   for v in row[rn_offset:index_start]]
  21         for value, field in zip_longest(row[index_start:], fields):
  22             values.append(self.query.convert_values(value, field, connection=self.connection))
  23         return tuple(values)
  24
  25     def as_sql(self, with_limits=True, with_col_aliases=False):
  26         """
  27         Creates the SQL for this query. Returns the SQL string and list
  28         of parameters.  This is overriden from the original Query class
  29         to handle the additional SQL Oracle requires to emulate LIMIT
  30         and OFFSET.
  31
  32         If 'with_limits' is False, any limit/offset information is not
  33         included in the query.
  34         """
  35         if with_limits and self.query.low_mark == self.query.high_mark:
  36             return '', ()
  37
  38         # The `do_offset` flag indicates whether we need to construct
  39         # the SQL needed to use limit/offset with Oracle.
  40         do_offset = with_limits and (self.query.high_mark is not None
  41                                      or self.query.low_mark)
  42         if not do_offset:
  43             sql, params = super(SQLCompiler, self).as_sql(with_limits=False,
  44                     with_col_aliases=with_col_aliases)
  45         else:
  46             sql, params = super(SQLCompiler, self).as_sql(with_limits=False,
  47                                                     with_col_aliases=True)
  48
  49             # Wrap the base query in an outer SELECT * with boundaries on
  50             # the "_RN" column.  This is the canonical way to emulate LIMIT
  51             # and OFFSET on Oracle.
  52             high_where = ''
  53             if self.query.high_mark is not None:
  54                 high_where = 'WHERE ROWNUM <= %d' % (self.query.high_mark,)
  55             sql = 'SELECT * FROM (SELECT ROWNUM AS "_RN", "_SUB".* FROM (%s) "_SUB" %s) WHERE "_RN" > %d' % (sql, high_where, self.query.low_mark)
  56
  57         return sql, params
  58
  59
  60 class SQLInsertCompiler(compiler.SQLInsertCompiler, SQLCompiler):
  61     pass
  62
  63 class SQLDeleteCompiler(compiler.SQLDeleteCompiler, SQLCompiler):
  64     pass
  65
  66 class SQLUpdateCompiler(compiler.SQLUpdateCompiler, SQLCompiler):
  67     pass
  68
  69 class SQLAggregateCompiler(compiler.SQLAggregateCompiler, SQLCompiler):
  70     pass
  71
  72 class SQLDateCompiler(compiler.SQLDateCompiler, SQLCompiler):
  73     pass