search/python/sortoptions.py

   1 #!/usr/bin/python
   2 #
   3 # Copyright 2012 Google Inc. All Rights Reserved.
   4
   5
   6 import logging
   7
   8 from google.appengine.api import search
   9
  10
  11 def get_sort_options(expressions=None, match_scorer=None, limit=1000):
  12   """Constructs sort options for 1.6.4 and 1.6.5 API differences.
  13
  14  An example of usage (NOTE: Do NOT set limit on SortExpression or MatchScorer):
  15
  16   expr_list = [
  17       search.SortExpression(expression='author', default_value='',
  18                             direction=search.SortExpression.DESCENDING)]
  19   sort_opts = get_sort_options(expression=expr_list, limit=sort_limit)
  20
  21   The returned value is used in constructing the query options:
  22
  23   options=search.QueryOptions(limit=doc_limit, sort_options=sort_opts)
  24
  25   Another example illustrating sorting on an expression based on a
  26   MatchScorer score:
  27
  28   expr_list = [
  29       search.SortExpression(expression='_score + 0.001 * rating',
  30                             default_value='',
  31                             direction=search.SortExpression.DESCENDING)]
  32   sort_opts = get_sort_options(expression=expr_list,
  33                               match_scorer=search.MatchScorer(),
  34                               limit=sort_limit)
  35
  36
  37   Args:
  38     expression: a list of search.SortExpression. Do not set limit parameter on
  39       SortExpression
  40     match_scorer: a search.MatchScorer or search.RescoringMatchScorer. Do not
  41       set limit parameter on either scorer
  42     limit: the scoring limit
  43
  44   Returns: the sort options value, either list of SortOption (1.6.4) or
  45   SortOptions (1.6.5), to set the sort_options field in the QueryOptions object.
  46   """
  47   try:
  48     # using 1.6.5 or greater
  49     if search.SortOptions:
  50       logging.info("search.SortOptions is defined.")
  51       return search.SortOptions(
  52           expressions=expressions, match_scorer=match_scorer, limit=limit)
  53
  54   # SortOptions not available, so using 1.6.4
  55   except AttributeError:
  56     logging.info("search.SortOptions is not defined.")
  57     expr_list = []
  58     # copy the sort expressions including the limit info
  59     if expressions:
  60       expr_list = [
  61           search.SortExpression(
  62               expression=e.expression, direction=e.direction,
  63               default_value=e.default_value, limit=limit)
  64           for e in expressions]
  65     # add the match scorer, if defined, to the expressions list.
  66     if isinstance(match_scorer, search.MatchScorer):
  67       expr_list.append(match_scorer.__class__(limit=limit))
  68     logging.debug("sort expressions: %s", expr_list)
  69     return expr_list