Batch process handling state groups
Erik Johnston
parent
67a1e315cc
commit
47a9da28ca
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@ -37,6 +37,7 @@ from synapse.metrics.background_process_metrics import run_as_background_process
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from synapse.storage.background_updates import BackgroundUpdateStore
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from synapse.storage.event_federation import EventFederationStore
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from synapse.storage.events_worker import EventsWorkerStore
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from synapse.storage.state import StateGroupWorkerStore
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from synapse.types import RoomStreamToken, get_domain_from_id
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from synapse.util.async_helpers import ObservableDeferred
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from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
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@ -203,7 +204,8 @@ def _retry_on_integrity_error(func):
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# inherits from EventFederationStore so that we can call _update_backward_extremities
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# and _handle_mult_prev_events (though arguably those could both be moved in here)
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class EventsStore(EventFederationStore, EventsWorkerStore, BackgroundUpdateStore):
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class EventsStore(StateGroupWorkerStore, EventFederationStore, EventsWorkerStore,
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BackgroundUpdateStore):
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EVENT_ORIGIN_SERVER_TS_NAME = "event_origin_server_ts"
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EVENT_FIELDS_SENDER_URL_UPDATE_NAME = "event_fields_sender_url"
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@ -1995,70 +1997,29 @@ class EventsStore(EventFederationStore, EventsWorkerStore, BackgroundUpdateStore
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logger.info("[purge] finding redundant state groups")
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# Get all state groups that are only referenced by events that are
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# to be deleted.
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# This works by first getting state groups that we may want to delete,
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# joining against event_to_state_groups to get events that use that
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# state group, then left joining against events_to_purge again. Any
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# state group where the left join produce *no nulls* are referenced
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# only by events that are going to be purged.
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# Get all state groups that are referenced by events that are to be
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# deleted. We then go and check if they are referenced by other events
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# or state groups, and if not we delete them.
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txn.execute("""
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SELECT state_group FROM
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(
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SELECT DISTINCT state_group FROM events_to_purge
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INNER JOIN event_to_state_groups USING (event_id)
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) AS sp
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INNER JOIN event_to_state_groups USING (state_group)
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LEFT JOIN events_to_purge AS ep USING (event_id)
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GROUP BY state_group
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HAVING SUM(CASE WHEN ep.event_id IS NULL THEN 1 ELSE 0 END) = 0
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SELECT DISTINCT state_group FROM events_to_purge
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INNER JOIN event_to_state_groups USING (event_id)
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""")
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state_rows = txn.fetchall()
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logger.info("[purge] found %i redundant state groups", len(state_rows))
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referenced_state_groups = set(sg for sg, in txn)
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logger.info(
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"[purge] found %i referenced state groups",
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len(referenced_state_groups),
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)
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# make a set of the redundant state groups, so that we can look them up
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# efficiently
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state_groups_to_delete = set([sg for sg, in state_rows])
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logger.info("[purge] finding state groups that can be deleted")
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# Now we get all the state groups that rely on these state groups
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logger.info("[purge] finding state groups which depend on redundant"
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" state groups")
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remaining_state_groups = []
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unreferenced_state_groups = 0
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for i in range(0, len(state_rows), 100):
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chunk = [sg for sg, in state_rows[i:i + 100]]
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# look for state groups whose prev_state_group is one we are about
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# to delete
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rows = self._simple_select_many_txn(
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txn,
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table="state_group_edges",
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column="prev_state_group",
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iterable=chunk,
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retcols=["state_group"],
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keyvalues={},
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)
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for row in rows:
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sg = row["state_group"]
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if sg in state_groups_to_delete:
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# exclude state groups we are about to delete: no point in
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# updating them
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continue
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if not self._is_state_group_referenced(txn, sg):
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# Let's also delete unreferenced state groups while we're
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# here, since otherwise we'd need to de-delta them
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state_groups_to_delete.add(sg)
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unreferenced_state_groups += 1
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continue
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remaining_state_groups.append(sg)
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state_groups_to_delete, remaining_state_groups = self._find_unreferenced_groups(
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txn, referenced_state_groups,
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)
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logger.info(
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"[purge] found %i extra unreferenced state groups to delete",
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unreferenced_state_groups,
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"[purge] found %i state groups to delete",
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len(state_groups_to_delete),
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)
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logger.info(
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@ -2109,11 +2070,11 @@ class EventsStore(EventFederationStore, EventsWorkerStore, BackgroundUpdateStore
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logger.info("[purge] removing redundant state groups")
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txn.executemany(
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"DELETE FROM state_groups_state WHERE state_group = ?",
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state_rows
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((sg,) for sg in state_groups_to_delete),
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)
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txn.executemany(
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"DELETE FROM state_groups WHERE id = ?",
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state_rows
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((sg,) for sg in state_groups_to_delete),
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)
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logger.info("[purge] removing events from event_to_state_groups")
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@ -1041,55 +1041,85 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
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return count
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def _is_state_group_referenced(self, txn, state_group):
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"""Checks if a given state group is referenced, or is safe to delete.
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def _find_unreferenced_groups(self, txn, state_groups):
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"""Used when purging history to figure out which state groups can be
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deleted and which need to be de-delta'ed (due to one of its prev groups
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being scheduled for deletion).
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A state group is referenced if it or any of its descendants are
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pointed at by an event. (A descendant is a state_group whose chain of
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prev_groups includes the given state_group.)
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Args:
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txn
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state_groups (set[int]): Set of state groups referenced by events
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that are going to be deleted.
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Returns:
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tuple[set[int], set[int]]: The set of state groups that can be
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deleted and the set of state groups that need to be de-delta'ed
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"""
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# Graph of state group -> previous group
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graph = {}
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# We check this by doing a depth first search to look for any
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# descendant referenced by `event_to_state_groups`.
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# Set of events that we have found to be referenced by events
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referenced_groups = set()
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# State groups we need to check, contains state groups that are
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# descendants of `state_group`
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state_groups_to_search = [state_group]
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# Set of state groups we've already seen
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state_groups_seen = set(state_groups)
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# Set of state groups we've already checked
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state_groups_searched = set()
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# Set of state groups to handle next.
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next_to_search = set(state_groups)
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while next_to_search:
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# We bound size of groups we're looking up at once, to stop the
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# SQL query getting too big
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if len(next_to_search) < 100:
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current_search = next_to_search
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next_to_search = set()
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else:
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lst = list(next_to_search)
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current_search = set(lst[:100])
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next_to_search = set(lst[100:])
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while state_groups_to_search:
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state_group = state_groups_to_search.pop() # Next state group to check
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# Check if state groups are referenced
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sql = """
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SELECT state_group, count(*) FROM event_to_state_groups
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LEFT JOIN events_to_purge AS ep USING (event_id)
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WHERE state_group IN (%s) AND ep.event_id IS NULL
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GROUP BY state_group
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""" % (",".join("?" for _ in current_search),)
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txn.execute(sql, list(current_search))
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is_referenced = self._simple_select_one_onecol_txn(
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txn,
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table="event_to_state_groups",
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keyvalues={"state_group": state_group},
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retcol="event_id",
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allow_none=True,
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)
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if is_referenced:
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# A descendant is referenced by event_to_state_groups, so
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# original state group is referenced.
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return True
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referenced = set(sg for sg, cnt in txn if cnt > 0)
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referenced_groups |= referenced
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state_groups_searched.add(state_group)
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# We don't continue iterating up the state group graphs for state
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# groups that are referenced.
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current_search -= referenced
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# Find all children of current state group and add to search
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references = self._simple_select_onecol_txn(
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rows = self._simple_select_many_txn(
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txn,
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table="state_group_edges",
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keyvalues={"prev_state_group": state_group},
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retcol="state_group",
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column="prev_state_group",
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iterable=current_search,
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keyvalues={},
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retcols=("prev_state_group", "state_group",),
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)
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state_groups_to_search.extend(references)
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# Lets be paranoid and check for cycles
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if state_groups_searched.intersection(references):
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raise Exception("State group %s has cyclic dependency", state_group)
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next_to_search.update(row["state_group"] for row in rows)
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# We don't bother re-handling groups we've already seen
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next_to_search -= state_groups_seen
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state_groups_seen |= next_to_search
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return False
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for row in rows:
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# Note: Each state group can have at most one prev group
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graph[row["state_group"]] = row["prev_state_group"]
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to_delete = state_groups_seen - referenced_groups
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to_dedelta = set()
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for sg in referenced_groups:
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prev_sg = graph.get(sg)
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if prev_sg and prev_sg in to_delete:
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to_dedelta.add(sg)
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return to_delete, to_dedelta
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class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
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