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signup: Avoid bloated Stream objects for default streams.

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Basically, I eliminate the use of select_all() in a query
that still makes a single round trip.  We have good test
enforcement that Django never needs to lazily fetch
objects off the Stream object. (It used to be common
to fetch stream.realm a while back, but we upgraded
bulk_add_subscription, in particular, a while back.)
This commit is contained in:
Steve Howell
2023-07-09 11:30:19 +00:00
committed by Tim Abbott
parent 8894ff89ac
commit 1156a50109
2 changed files with 22 additions and 26 deletions
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31
zerver/lib/default_streams.py
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@@ -4,14 +4,18 @@ from zerver.lib.types import APIStreamDict
from zerver.models import DefaultStream, Stream
def get_default_streams_for_realm(realm_id: int) -> List[Stream]:
# TODO: Deprecate this extremely expensive query. We can't immediately
# just improve it by removing select_related(), because then you
# may get the opposite problem of multiple round trips.
return [
default.stream
for default in DefaultStream.objects.select_related().filter(realm_id=realm_id)
]
def get_slim_realm_default_streams(realm_id: int) -> List[Stream]:
# We really want this query to be simple and just get "thin" Stream objects
# in one round trip.
#
# The above is enforced by at least three tests that verify query counts,
# and test_query_count in test_subs.py makes sure that the query itself is
# not like 11000 bytes, which is what we had in a prior version that used
# select_related() with not arguments (and thus joined to too many tables).
#
# Please be careful about modifying this code, as it has had a history
# of performance problems.
return list(Stream.objects.filter(defaultstream__realm_id=realm_id))
def get_default_stream_ids_for_realm(realm_id: int) -> Set[int]:
@@ -23,11 +27,6 @@ def get_default_streams_for_realm_as_dicts(realm_id: int) -> List[APIStreamDict]
Return all the default streams for a realm using a list of dictionaries sorted
by stream name.
"""
# This slightly convoluted construction makes it so that the Django ORM gets
# all the data it needs to serialize default streams as a list of dictionaries
# using a single query without using select_related().
# This is enforced by test_query_count in test_subs.py.
stream_ids = DefaultStream.objects.filter(realm_id=realm_id).values_list("stream_id")
streams = Stream.objects.filter(id__in=stream_ids)
return sorted((stream.to_dict() for stream in streams), key=lambda elt: elt["name"])
streams = get_slim_realm_default_streams(realm_id)
stream_dicts = [stream.to_dict() for stream in streams]
return sorted(stream_dicts, key=lambda stream: stream["name"])