Implement asynchronus cursor (refs #19)

[laughingman7743]

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import concurrent

from pyathena import connect
from pyathena.async_cursor import AsyncCursor


def done_callback(future):
    result_set = future.result()
    print(result_set.state)
    print(result_set.description)
    for r in result_set:
        print(r)


def main():
    futures = []
    cursor = connect(s3_staging_dir='s3://YOUR_BUCKET/path/to/',
                     region_name='us-west-2',
                     cursor_class=AsyncCursor).cursor(max_workers=10)

    query_id, future = cursor.execute("SELECT * FROM many_rows LIMIT 10")
    print(query_id)
    future.add_done_callback(done_callback)
    futures.append(future)

    query_id, future = cursor.execute("SELECT * FROM one_row_complex")
    print(query_id)
    future.add_done_callback(done_callback)
    futures.append(future)

    query_id, future = cursor.execute("SELECT does_not_exist FROM this_really_does_not_exist")
    print(query_id)
    future.add_done_callback(done_callback)
    futures.append(future)

    # blocking
    for _ in concurrent.futures.as_completed(futures):
        pass
    # shutdown all worker
    cursor.close()


if __name__ == '__main__':
    main()

[codecov-io]

Codecov Report

Merging #21 into master will increase coverage by 1.92%.
The diff coverage is 91.94%.

@@            Coverage Diff             @@
##           master      #21      +/-   ##
==========================================
+ Coverage   90.29%   92.22%   +1.92%     
==========================================
  Files           8       12       +4     
  Lines         567      772     +205     
==========================================
+ Hits          512      712     +200     
- Misses         55       60       +5

Impacted Files	Coverage Δ
pyathena/connection.py	92% <100%> (+0.51%)	⬆️
pyathena/cursor.py	100% <100%> (+11.88%)	⬆️
pyathena/__init__.py	82.14% <100%> (ø)	⬆️
pyathena/result_set.py	89.18% <89.18%> (ø)
pyathena/common.py	89.9% <89.9%> (ø)
pyathena/model.py	92.15% <92.15%> (ø)
pyathena/async_cursor.py	93.47% <93.47%> (ø)
... and 1 more

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[SamProtas]

👍 Looking forward to this feature. Thanks!