Fix queries with wildcards

[esemeniuc]

This patch fixes queries that use wildcards (%) in SQLAlchemy. The params argument is an empty dict if no extra parameters are provided. This causes line 256 of presto.py to always branch to the else case, which causes an error (see the bottom).

Here is a minimal example to trigger the bug:

from sqlalchemy.engine import create_engine
engine = create_engine('presto://localhost:8080/hive/importdemo4')
engine.execute("CREATE TABLE demo_table (X VARCHAR)")
resultProxy = engine.execute("SELECT * FROM demo_table where x like 'a%'")
print(resultProxy.fetchone())

Resulting error:

Traceback (most recent call last):
  File "/Users/e.semeniuc/dev/SDB-Health-Report/prestodemo.py", line 31, in <module>
    resultProxy = engine.execute("SELECT * FROM demo_table where x like 'a%'")
  File "/Users/e.semeniuc/dev/SDB-Health-Report/venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py", line 2238, in execute
    return connection.execute(statement, *multiparams, **params)
  File "/Users/e.semeniuc/dev/SDB-Health-Report/venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py", line 1006, in execute
    return self._execute_text(object_, multiparams, params)
  File "/Users/e.semeniuc/dev/SDB-Health-Report/venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py", line 1175, in _execute_text
    ret = self._execute_context(
  File "/Users/e.semeniuc/dev/SDB-Health-Report/venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py", line 1317, in _execute_context
    self._handle_dbapi_exception(
  File "/Users/e.semeniuc/dev/SDB-Health-Report/venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py", line 1515, in _handle_dbapi_exception
    util.raise_(exc_info[1], with_traceback=exc_info[2])
  File "/Users/e.semeniuc/dev/SDB-Health-Report/venv/lib/python3.8/site-packages/sqlalchemy/util/compat.py", line 178, in raise_
    raise exception
  File "/Users/e.semeniuc/dev/SDB-Health-Report/venv/lib/python3.8/site-packages/sqlalchemy/engine/base.py", line 1277, in _execute_context
    self.dialect.do_execute(
  File "/Users/e.semeniuc/dev/SDB-Health-Report/venv/lib/python3.8/site-packages/sqlalchemy/engine/default.py", line 593, in do_execute
    cursor.execute(statement, parameters)
  File "/Users/e.semeniuc/dev/SDB-Health-Report/venv/lib/python3.8/site-packages/pyhive/presto.py", line 249, in execute
    sql = operation % _escaper.escape_args(parameters)
ValueError: unsupported format character ''' (0x27) at index 41

[codecov[bot]]

Codecov Report

Merging #351 (6ef94d1) into master (1548ecc) will decrease coverage by 0.12%. The diff coverage is 100.00%.

:exclamation: Current head 6ef94d1 differs from pull request most recent head 80691ff. Consider uploading reports for the commit 80691ff to get more accurate results

@@            Coverage Diff             @@
##           master     #351      +/-   ##
==========================================
- Coverage   93.36%   93.23%   -0.13%     
==========================================
  Files          14       14              
  Lines        1553     1553              
  Branches      167      167              
==========================================
- Hits         1450     1448       -2     
- Misses         75       77       +2     
  Partials       28       28              

Impacted Files	Coverage Δ
pyhive/presto.py	85.27% <100.00%> (-1.23%)	:arrow_down:

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[esemeniuc]

Could I get a review?

[esemeniuc]

Follow up if this can be merged

[Khrol]

We are also affected by this issue. Is there any way to merge/release this PR?

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