predictors: db tool workaround to solve sqlite3 compatibility problem.

tools/resource_prefetch_predictor/prefetch_predictor_tool.py

 #!/usr/bin/python
 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Inspection of the prefetch predictor database.
 
 On Android, the database can be extracted using:
 adb pull \
   '/data/user/0/$package_name/app_chrome/Default/Network Action Predictor'
   predictor_db
 """
 
 import argparse
 import sqlite3
+import os
 
 from resource_prefetch_predictor_pb2 import (PrefetchData, ResourceData)
 
 
 class Entry(object):
   """Represents an entry in the predictor database."""
   def __init__(
       self, primary_key, proto_buffer):
     self.primary_key = primary_key
     self.prefetch_data = PrefetchData()
@@ skipping 44 matching lines @@
   def PrettyPrintCandidates(self):
     """Prints the candidates for prefetch."""
     print 'primary_key: %s' % self.prefetch_data.primary_key
     for resource in self.prefetch_data.resources:
       confidence = float(resource.number_of_hits) / (
           resource.number_of_hits + resource.number_of_misses)
       if resource.number_of_hits < 2 or confidence < .7:
         continue
       self._PrettyPrintResource(resource)
 
+# The version of python sqlite3 library we have in Ubuntu 14.04 LTS doesn't
+# support views but command line util does.
+# TODO(alexilin): get rid of this when python sqlite3 adds view support.
+def CreateCompatibleDatabaseCopy(filename):
+  import tempfile, shutil, subprocess
+  _, tmpfile = tempfile.mkstemp()
+  shutil.copy2(filename, tmpfile)
+  subprocess.call(['sqlite3', tmpfile, 'DROP VIEW MmapStatus'])
+  return tmpfile
 
 def DatabaseStats(filename, domain):
   connection = sqlite3.connect(filename)
   c = connection.cursor()
   query = ('SELECT key, proto FROM resource_prefetch_predictor_host')
   entries = [Entry.FromRow(row) for row in c.execute(query)]
   for x in entries:
     if domain is None or x.primary_key == domain:
       x.PrettyPrintCandidates()
 
 
 def main():
   parser = argparse.ArgumentParser()
   parser.add_argument('-f', dest='database_filename', required=True,
                       help='Path to the database')
   parser.add_argument('-d', dest='domain', default=None, help='Domain')
   args = parser.parse_args()
-  DatabaseStats(args.database_filename, args.domain)
+  try:
+    database_copy = CreateCompatibleDatabaseCopy(args.database_filename)
+    DatabaseStats(database_copy, args.domain)
+  finally:
+    if os.path.exists(database_copy):
+      os.remove(database_copy)
 
 
 if __name__ == '__main__':
   main()