tests/comparison/data_generator_mapper.py

#!/usr/bin/env python
#
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# to you under the Apache License, Version 2.0 (the
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#   http://www.apache.org/licenses/LICENSE-2.0
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'''This is a mapper for use with hadoop streaming. See data_generator.DatabasePopulator
   for more information on how this file is used.
'''

import os
import random
import sys

# When running locally, the PYTHONPATH needed by impala-shell interferes with python
# through YARN. Specifically, when the data generator needs to import common.py, python
# looks at $IMPALA_HOME/tests/common and errors when it doesn't find what was asked for.
sys.path.insert(1, os.getcwd())

from data_generator_mapred_common import (
    deserialize,
    estimate_rows_per_reducer,
    MB_PER_REDUCER,
    serialize)

for line in sys.stdin:
  table_data_generator = deserialize(line)
  random.seed(table_data_generator.randomization_seed)
  row_count = table_data_generator.row_count
  rows_per_batch = estimate_rows_per_reducer(table_data_generator, MB_PER_REDUCER)
  batch_idx = 0
  while row_count > 0:
    table_data_generator.row_count = min(row_count, rows_per_batch)
    table_data_generator.randomization_seed = int(random.random() * sys.maxint)

    # Generate input for the reducers.
    print("%s\t%s\t%s" % (table_data_generator.table.name, batch_idx,
        serialize(table_data_generator)))

    batch_idx += 1
    row_count -= rows_per_batch