src/dctv/subset.py

# Copyright (C) 2020 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http:#www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Utility to extract parts of a trace based on a SQL expression"""
import sys
import logging

from .model import TraceAnalysisSession, FileTraceContext
from .sql import identifier_quote
from ._native import dump_events_to_fd
from .util import ureg

log = logging.getLogger(__name__)

def run_subset(*,
               trace_file_name,
               filter_expression,
               absolute_time=False,
               out_file=None):
  """Run the subset command-line utility"""
  trace_session = TraceAnalysisSession()
  time_basis_override = 0 if absolute_time else None
  trace_session.mount_trace(["trace"],
                            FileTraceContext(
                              trace_file_name,
                              time_basis_override=time_basis_override),
                            temp_hack_lenient_metadata=True)
  q = "SELECT type FROM trace.found_event_types"
  found_event_types = trace_session.sql_query1(q).tolist()
  if not found_event_types:
    log.warning("no events found in trace?!")
    return

  def _query_for_event_type(event_type):
    return "SELECT _pos FROM trace.raw_events.{} WHERE ({})".format(
      identifier_quote(event_type), filter_expression)
  queries = [_query_for_event_type(event_type)
             for event_type in found_event_types]

  valid_queries = []
  for event_type, query in zip(found_event_types, queries):
    try:
      trace_session.parse_sql_query(query)
    except Exception as ex:
      log.warning("query %r does not work for event type %r: "
                  "filtering out this event type", query, event_type)
      log.warning("query error was %r", ex)
      continue
    valid_queries.append(query)
  if not valid_queries:
    log.warning("no events could, syntactically, match filter!")
    return
  q = " UNION ALL ".join(
    "({})".format(query) for query in valid_queries) + " ORDER BY _pos"

  cursor = trace_session.sql_query(q,
                                   output_format="rows",
                                   want_schema=True)
  trace_info = trace_session.get_mounted_trace(["trace"])
  nr_cpus = trace_info.metadata.get("nr_cpus")
  out_file = out_file or sys.stdout
  if nr_cpus is not None:
    out_file.write("cpus={}\n".format(nr_cpus))
    out_file.flush()
  mapping = trace_info.mapped_trace.mapping
  for row, _is_eof in cursor:
    pos_array, pos_schema = row["_pos"]
    assert pos_schema.unit == ureg().bytes
    dump_events_to_fd(mapping, pos_array, out_file.fileno())
  out_file.flush()