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# Copyright (C) 2008, One Laptop Per Child
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
import logging
import time
import os
import gobject
import xapian
from xapian import WritableDatabase, Document, Enquire, Query, QueryParser
from olpc.datastore import layoutmanager
from olpc.datastore.layoutmanager import MAX_QUERY_LIMIT
_VALUE_UID = 0
_VALUE_TIMESTAMP = 1
_PREFIX_UID = 'Q'
_PREFIX_ACTIVITY = 'A'
_PREFIX_MIME_TYPE = 'M'
# Force a flush every _n_ changes to the db
_FLUSH_THRESHOLD = 20
# Force a flush after _n_ seconds since the last change to the db
_FLUSH_TIMEOUT = 60
_PROPERTIES_NOT_TO_INDEX = ['timestamp', 'activity_id', 'keep', 'preview']
_MAX_RESULTS = int(2 ** 31 - 1)
class IndexStore(object):
"""Index metadata and provide rich query facilities on it.
"""
def __init__(self):
self._database = None
self._flush_timeout = None
self._pending_writes = 0
def open_index(self):
index_path = layoutmanager.get_instance().get_index_path()
self._database = WritableDatabase(index_path, xapian.DB_CREATE_OR_OPEN)
def close_index(self):
self._database.flush()
self._database = None
def remove_index(self):
index_path = layoutmanager.get_instance().get_index_path()
if not os.path.exists(index_path):
return
for f in os.listdir(index_path):
os.remove(os.path.join(index_path, f))
def contains(self, uid):
postings = self._database.postlist(_PREFIX_UID + uid)
try:
postlist_item = postings.next()
except StopIteration:
return False
return True
def store(self, uid, properties):
document = Document()
document.add_term(_PREFIX_UID + uid)
document.add_term(_PREFIX_ACTIVITY + properties.get('activity', ''))
document.add_term(_PREFIX_MIME_TYPE + properties['mime_type'])
document.add_value(_VALUE_UID, uid)
document.add_value(_VALUE_TIMESTAMP, str(properties['timestamp']))
term_generator = xapian.TermGenerator()
# TODO: we should do stemming, but in which language?
#if language is not None:
# term_generator.set_stemmer(_xapian.Stem(language))
# TODO: we should use a stopper
#if stop is not None:
# stopper = _xapian.SimpleStopper()
# for term in stop:
# stopper.add (term)
# term_generator.set_stopper (stopper)
term_generator.set_document(document)
term_generator.index_text_without_positions(
self._extract_text(properties), 1, '')
if not self.contains(uid):
self._database.add_document(document)
else:
self._database.replace_document(_PREFIX_UID + uid, document)
self._flush()
def _extract_text(self, properties):
text = ''
for key, value in properties.items():
if key not in _PROPERTIES_NOT_TO_INDEX:
if text:
text += ' '
if isinstance(value, unicode):
value = value.encode('utf-8')
elif not isinstance(value, basestring):
value = str(value)
text += value
return text
def find(self, query):
enquire = Enquire(self._database)
enquire.set_query(self._parse_query(query))
offset = query.get('offset', 0)
limit = query.get('limit', MAX_QUERY_LIMIT)
# This will assure that the results count is exact.
check_at_least = offset + limit + 1
enquire.set_sort_by_value(_VALUE_TIMESTAMP, True)
query_result = enquire.get_mset(offset, limit, check_at_least)
total_count = query_result.get_matches_estimated()
uids = []
for hit in query_result:
uids.append(hit.document.get_value(_VALUE_UID))
return (uids, total_count)
def _parse_query(self, query_dict):
logging.debug('_parse_query %r' % query_dict)
queries = []
if query_dict.has_key('query'):
query_parser = QueryParser()
query_parser.set_database(self._database)
#query_parser.set_default_op(Query.OP_AND)
# TODO: we should do stemming, but in which language?
#query_parser.set_stemmer(_xapian.Stem(lang))
#query_parser.set_stemming_strategy(qp.STEM_SOME)
query = query_parser.parse_query(
query_dict['query'],
QueryParser.FLAG_PHRASE |
QueryParser.FLAG_BOOLEAN |
QueryParser.FLAG_LOVEHATE |
QueryParser.FLAG_WILDCARD,
'')
queries.append(query)
self._replace_mtime(query_dict)
if query_dict.has_key('timestamp'):
start = str(query_dict['timestamp'].pop('start', 0))
end = str(query_dict['timestamp'].pop('end', _MAX_RESULTS))
query = Query(Query.OP_VALUE_RANGE, _VALUE_TIMESTAMP, start, end)
queries.append(query)
if query_dict.has_key('uid'):
queries.append(Query(_PREFIX_UID + query_dict['uid']))
if query_dict.has_key('activity'):
queries.append(Query(_PREFIX_ACTIVITY + query_dict['activity']))
if query_dict.has_key('mime_type'):
mime_queries = []
for mime_type in query_dict['mime_type']:
mime_queries.append(Query(_PREFIX_MIME_TYPE + mime_type))
queries.append(Query(Query.OP_OR, mime_queries))
if not queries:
queries.append(Query(''))
return Query(Query.OP_AND, queries)
def _replace_mtime(self, query):
# TODO: Just a hack for the current journal that filters by mtime
DATE_FORMAT = '%Y-%m-%dT%H:%M:%S'
if query.has_key('mtime'):
mtime_range = query.pop('mtime')
start = mtime_range['start'][:-7]
start = time.mktime(time.strptime(start, DATE_FORMAT))
end = mtime_range['end'][:-7]
# FIXME: this will give an unexpected result if the journal is in a
# different timezone
end = time.mktime(time.strptime(end, DATE_FORMAT))
query['timestamp'] = {'start': int(start), 'end': int(end)}
def delete(self, uid):
self._database.delete_document(_PREFIX_UID + uid)
def get_activities(self):
activities = []
for term in self._database.allterms(_PREFIX_ACTIVITY):
activities.append(term.term[len(_PREFIX_ACTIVITY):])
return activities
def _flush_timeout_cb(self):
self._flush(True)
return False
def _flush(self, force=False):
"""Called after any database mutation"""
logging.debug('IndexStore.flush: %r %r' % (force, self._pending_writes))
if self._flush_timeout is not None:
gobject.source_remove(self._flush_timeout)
self._flush_timeout = None
self._pending_writes += 1
if force or self._pending_writes > _FLUSH_THRESHOLD:
self._database.flush()
self._pending_writes = 0
else:
self._flush_timeout = gobject.timeout_add(_FLUSH_TIMEOUT * 1000,
self._flush_timeout_cb)
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