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1553dc00e0
This class encapsulates the mapping of stream ids to recipient ids, and it is optimized for bulk use and repeated use (i.e. it remembers values it already fetched). This particular commit barely improves the performance of gather_subscriptions_helper, but it sets us up for further optimizations. Long term, we may try to denormalize stream_id on to the Subscriber table or otherwise modify the database so we don't have to jump through hoops to do this kind of mapping. This commit will help enable those changes, because we isolate the mapping to this one new class.
103 lines
3.3 KiB
Python
103 lines
3.3 KiB
Python
from __future__ import absolute_import
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from __future__ import print_function
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from typing import (Dict, List)
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from django.db import connection
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from zerver.models import Recipient
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class StreamRecipientMap(object):
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'''
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This class maps stream_id -> recipient_id and vice versa.
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It is useful for bulk operations. Call the populate_* methods
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to initialize the data structures. You should try to avoid
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excessive queries by finding ids up front, but you can call
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this repeatedly, and it will only look up new ids.
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You should ONLY use this class for READ operations.
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Note that this class uses raw SQL, because we want to highly
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optimize page loads.
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'''
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def __init__(self):
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# type: () -> None
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self.recip_to_stream = dict() # type: Dict[int, int]
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self.stream_to_recip = dict() # type: Dict[int, int]
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def populate_for_stream_ids(self, stream_ids):
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# type: (List[int]) -> None
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stream_ids = sorted([
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stream_id for stream_id in stream_ids
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if stream_id not in self.stream_to_recip
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])
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if not stream_ids:
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return
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# see comment at the top of the class
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id_list = ', '.join(str(stream_id) for stream_id in stream_ids)
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query = '''
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SELECT
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zerver_recipient.id as recipient_id,
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zerver_stream.id as stream_id
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FROM
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zerver_stream
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INNER JOIN zerver_recipient ON
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zerver_stream.id = zerver_recipient.type_id
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WHERE
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zerver_recipient.type = %d
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AND
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zerver_stream.id in (%s)
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''' % (Recipient.STREAM, id_list)
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self._process_query(query)
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def populate_for_recipient_ids(self, recipient_ids):
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# type: (List[int]) -> None
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recipient_ids = sorted([
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recip_id for recip_id in recipient_ids
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if recip_id not in self.recip_to_stream
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])
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if not recipient_ids:
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return
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# see comment at the top of the class
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id_list = ', '.join(str(recip_id) for recip_id in recipient_ids)
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query = '''
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SELECT
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zerver_recipient.id as recipient_id,
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zerver_stream.id as stream_id
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FROM
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zerver_recipient
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INNER JOIN zerver_stream ON
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zerver_stream.id = zerver_recipient.type_id
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WHERE
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zerver_recipient.type = %d
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AND
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zerver_recipient.id in (%s)
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''' % (Recipient.STREAM, id_list)
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self._process_query(query)
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def _process_query(self, query):
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# type: (str) -> None
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cursor = connection.cursor()
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cursor.execute(query)
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rows = cursor.fetchall()
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cursor.close()
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for recip_id, stream_id in rows:
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self.recip_to_stream[recip_id] = stream_id
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self.stream_to_recip[stream_id] = recip_id
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def recipient_id_for(self, stream_id):
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# type: (int) -> int
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return self.stream_to_recip[stream_id]
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def stream_id_for(self, recip_id):
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# type: (int) -> int
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return self.recip_to_stream[recip_id]
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def recipient_to_stream_id_dict(self):
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# type: () -> Dict[int, int]
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return self.recip_to_stream
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