sdks/python/apache_beam/testing/benchmarks/nexmark/queries/query7.py

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"""
Query 7, 'Highest Bid'. Select the bids with the highest bid price in the
last minute. In CQL syntax::

  SELECT Rstream(B.auction, B.price, B.bidder)
  FROM Bid [RANGE 1 MINUTE SLIDE 1 MINUTE] B
  WHERE B.price = (SELECT MAX(B1.price)
                   FROM BID [RANGE 1 MINUTE SLIDE 1 MINUTE] B1);

We will use a shorter window to help make testing easier. We'll also
implement this using a side-input in order to exercise that functionality.
(A combiner, as used in Query 5, is a more efficient approach.).
"""

import apache_beam as beam
from apache_beam.testing.benchmarks.nexmark.queries import nexmark_query_util
from apache_beam.transforms import window


def load(events, metadata=None, pipeline_options=None):
  # window bids into fixed window
  sliding_bids = (
      events
      | nexmark_query_util.JustBids()
      | beam.WindowInto(window.FixedWindows(metadata.get('window_size_sec'))))
  # find the largest price in all bids per window
  max_prices = (
      sliding_bids
      | beam.Map(lambda bid: bid.price)
      | beam.CombineGlobally(max).without_defaults())
  return (
      sliding_bids
      | 'select_bids' >> beam.ParDo(
          SelectMaxBidFn(), beam.pvalue.AsSingleton(max_prices)))


class SelectMaxBidFn(beam.DoFn):
  def process(self, element, max_bid_price):
    if element.price == max_bid_price:
      yield element