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https://github.com/element-hq/synapse
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Delete unreferened state groups during purge
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parent
d86794325f
commit
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2 changed files with 77 additions and 6 deletions
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@ -2025,6 +2025,7 @@ class EventsStore(EventFederationStore, EventsWorkerStore, BackgroundUpdateStore
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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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@ -2037,13 +2038,33 @@ class EventsStore(EventFederationStore, EventsWorkerStore, BackgroundUpdateStore
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retcols=["state_group"],
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keyvalues={},
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)
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remaining_state_groups.extend(
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row["state_group"] for row in rows
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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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if row["state_group"] not in state_groups_to_delete
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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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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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)
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logger.info(
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"[purge] de-delta-ing %i remaining state groups",
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len(remaining_state_groups),
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)
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# Now we turn the state groups that reference to-be-deleted state
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# groups to non delta versions.
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@ -1041,6 +1041,56 @@ 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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A state groups is referenced if it or any of its descendants are
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pointed at by an event. (A descendant is a group which has the given
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state_group as a prev group)
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"""
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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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# 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 checked
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state_groups_searched = set()
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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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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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state_groups_searched.add(state_group)
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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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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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)
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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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return False
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class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
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""" Keeps track of the state at a given event.
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