Alternative PR for: Some bytes/str issues in py3 w/ zlib and json (#2558)

* sql_lab.py: compress via utils

* utils.py: added zlib_compress and zlib_compress_to_string

* core.py: converted to use zlib_decompress_to_string; renamed uncompress to decompress in utils.py

* utils_tests.py: added test for compress/decompress

* fixed broken utils test; removed redundant code and empty lines from utils.py

* utils.py: corrected docstrings, removed unnecessary 'else'

* removed yet another superfluous else

superset/sql_lab.py

@@ -6,7 +6,6 @@ import logging
 import pandas as pd
 import sqlalchemy
 import uuid
-import zlib
 
 from sqlalchemy.pool import NullPool
 from sqlalchemy.orm import sessionmaker
@@ -185,7 +184,7 @@ def get_sql_results(self, query_id, return_results=True, store_results=False):
     if store_results:
         key = '{}'.format(uuid.uuid4())
         logging.info("Storing results in results backend, key: {}".format(key))
-        results_backend.set(key, zlib.compress(payload))
+        results_backend.set(key, utils.zlib_compress(payload))
         query.results_key = key
 
     session.merge(query)

superset/utils.py

@@ -16,6 +16,8 @@ import smtplib
 import sqlalchemy as sa
 import signal
 import uuid
+import sys
+import zlib
 
 from builtins import object
 from datetime import date, datetime, time
@@ -41,7 +43,7 @@ from sqlalchemy.types import TypeDecorator, TEXT
 
 logging.getLogger('MARKDOWN').setLevel(logging.INFO)
 
-
+PY3K = sys.version_info >= (3, 0)
 EPOCH = datetime(1970, 1, 1)
 DTTM_ALIAS = '__timestamp'
 
@@ -572,3 +574,34 @@ def setup_cache(app, cache_config):
     """Setup the flask-cache on a flask app"""
     if cache_config and cache_config.get('CACHE_TYPE') != 'null':
         return Cache(app, config=cache_config)
+
+
+def zlib_compress(data):
+    """
+    Compress things in a py2/3 safe fashion
+    >>> json_str = '{"test": 1}'
+    >>> blob = zlib_compress(json_str)
+    """
+    if PY3K:
+        if isinstance(data, str):
+            return zlib.compress(bytes(data, "utf-8"))
+        return zlib.compress(data)
+    return zlib.compress(data)
+
+
+def zlib_decompress_to_string(blob):
+    """
+    Decompress things to a string in a py2/3 safe fashion
+    >>> json_str = '{"test": 1}'
+    >>> blob = zlib_compress(json_str)
+    >>> got_str = zlib_decompress_to_string(blob)
+    >>> got_str == json_str
+    True
+    """
+    if PY3K:
+        if isinstance(blob, bytes):
+            decompressed = zlib.decompress(blob)
+        else:
+            decompressed = zlib.decompress(bytes(blob, "utf-8"))
+        return decompressed.decode("utf-8")
+    return zlib.decompress(blob)

superset/views/core.py

@@ -11,7 +11,6 @@ import pickle
 import re
 import time
 import traceback
-import zlib
 
 import sqlalchemy as sqla
 
@@ -1878,7 +1877,7 @@ class Superset(BaseSupersetView):
             return json_error_response(get_datasource_access_error_msg(
                 '{}'.format(rejected_tables)))
 
-        payload = zlib.decompress(blob)
+        payload = utils.zlib_decompress_to_string(blob)
         display_limit = app.config.get('DISPLAY_SQL_MAX_ROW', None)
         if display_limit:
             payload_json = json.loads(payload)
@@ -2018,7 +2017,7 @@ class Superset(BaseSupersetView):
         if results_backend and query.results_key:
             blob = results_backend.get(query.results_key)
         if blob:
-            json_payload = zlib.decompress(blob)
+            json_payload = utils.zlib_decompress_to_string(blob)
             obj = json.loads(json_payload)
             columns = [c['name'] for c in obj['columns']]
             df = pd.DataFrame.from_records(obj['data'], columns=columns)

tests/utils_tests.py

@@ -1,7 +1,7 @@
 from datetime import datetime, date, timedelta, time
 from decimal import Decimal
 from superset.utils import (
-    json_int_dttm_ser, json_iso_dttm_ser, base_json_conv, parse_human_timedelta
+    json_int_dttm_ser, json_iso_dttm_ser, base_json_conv, parse_human_timedelta, zlib_compress, zlib_decompress_to_string
 )
 import unittest
 import uuid
@@ -45,3 +45,10 @@ class UtilsTestCase(unittest.TestCase):
     def test_parse_human_timedelta(self, mock_now):
         mock_now.return_value = datetime(2016, 12, 1)
         self.assertEquals(parse_human_timedelta('now'), timedelta(0))
+
+    def test_zlib_compression(self):
+        json_str = """{"test": 1}"""
+        blob = zlib_compress(json_str)
+        got_str = zlib_decompress_to_string(blob)
+        self.assertEquals(json_str, got_str)
+