diff --git a/synapse/events/snapshot.py b/synapse/events/snapshot.py
index 6eaef8b57a..e0d82ad81c 100644
--- a/synapse/events/snapshot.py
+++ b/synapse/events/snapshot.py
@@ -11,6 +11,7 @@
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
+from abc import ABC, abstractmethod
from typing import TYPE_CHECKING, List, Optional, Tuple
import attr
@@ -26,8 +27,51 @@ if TYPE_CHECKING:
from synapse.types.state import StateFilter
+class UnpersistedEventContextBase(ABC):
+ """
+ This is a base class for EventContext and UnpersistedEventContext, objects which
+ hold information relevant to storing an associated event. Note that an
+ UnpersistedEventContexts must be converted into an EventContext before it is
+ suitable to send to the db with its associated event.
+
+ Attributes:
+ _storage: storage controllers for interfacing with the database
+ app_service: If the associated event is being sent by a (local) application service, that
+ app service.
+ """
+
+ def __init__(self, storage_controller: "StorageControllers"):
+ self._storage: "StorageControllers" = storage_controller
+ self.app_service: Optional[ApplicationService] = None
+
+ @abstractmethod
+ async def persist(
+ self,
+ event: EventBase,
+ ) -> "EventContext":
+ """
+ A method to convert an UnpersistedEventContext to an EventContext, suitable for
+ sending to the database with the associated event.
+ """
+ pass
+
+ @abstractmethod
+ async def get_prev_state_ids(
+ self, state_filter: Optional["StateFilter"] = None
+ ) -> StateMap[str]:
+ """
+ Gets the room state at the event (ie not including the event if the event is a
+ state event).
+
+ Args:
+ state_filter: specifies the type of state event to fetch from DB, example:
+ EventTypes.JoinRules
+ """
+ pass
+
+
@attr.s(slots=True, auto_attribs=True)
-class EventContext:
+class EventContext(UnpersistedEventContextBase):
"""
Holds information relevant to persisting an event
@@ -77,9 +121,6 @@ class EventContext:
delta_ids: If ``prev_group`` is not None, the state delta between ``prev_group``
and ``state_group``.
- app_service: If this event is being sent by a (local) application service, that
- app service.
-
partial_state: if True, we may be storing this event with a temporary,
incomplete state.
"""
@@ -122,6 +163,9 @@ class EventContext:
"""Return an EventContext instance suitable for persisting an outlier event"""
return EventContext(storage=storage)
+ async def persist(self, event: EventBase) -> "EventContext":
+ return self
+
async def serialize(self, event: EventBase, store: "DataStore") -> JsonDict:
"""Converts self to a type that can be serialized as JSON, and then
deserialized by `deserialize`
@@ -254,6 +298,128 @@ class EventContext:
)
+@attr.s(slots=True, auto_attribs=True)
+class UnpersistedEventContext(UnpersistedEventContextBase):
+ """
+ The event context holds information about the state groups for an event. It is important
+ to remember that an event technically has two state groups: the state group before the
+ event, and the state group after the event. If the event is not a state event, the state
+ group will not change (ie the state group before the event will be the same as the state
+ group after the event), but if it is a state event the state group before the event
+ will differ from the state group after the event.
+ This is a version of an EventContext before the new state group (if any) has been
+ computed and stored. It contains information about the state before the event (which
+ also may be the information after the event, if the event is not a state event). The
+ UnpersistedEventContext must be converted into an EventContext by calling the method
+ 'persist' on it before it is suitable to be sent to the DB for processing.
+
+ state_group_after_event:
+ The state group after the event. This will always be None until it is persisted.
+ If the event is not a state event, this will be the same as
+ state_group_before_event.
+
+ state_group_before_event:
+ The ID of the state group representing the state of the room before this event.
+
+ state_delta_due_to_event:
+ If the event is a state event, then this is the delta of the state between
+ `state_group` and `state_group_before_event`
+
+ prev_group_for_state_group_before_event:
+ If it is known, ``state_group_before_event``'s previous state group.
+
+ delta_ids_to_state_group_before_event:
+ If ``prev_group_for_state_group_before_event`` is not None, the state delta
+ between ``prev_group_for_state_group_before_event`` and ``state_group_before_event``.
+
+ partial_state:
+ Whether the event has partial state.
+
+ state_map_before_event:
+ A map of the state before the event, i.e. the state at `state_group_before_event`
+ """
+
+ _storage: "StorageControllers"
+ state_group_before_event: Optional[int]
+ state_group_after_event: Optional[int]
+ state_delta_due_to_event: Optional[dict]
+ prev_group_for_state_group_before_event: Optional[int]
+ delta_ids_to_state_group_before_event: Optional[StateMap[str]]
+ partial_state: bool
+ state_map_before_event: Optional[StateMap[str]] = None
+
+ async def get_prev_state_ids(
+ self, state_filter: Optional["StateFilter"] = None
+ ) -> StateMap[str]:
+ """
+ Gets the room state map, excluding this event.
+
+ Args:
+ state_filter: specifies the type of state event to fetch from DB
+
+ Returns:
+ Maps a (type, state_key) to the event ID of the state event matching
+ this tuple.
+ """
+ if self.state_map_before_event:
+ return self.state_map_before_event
+
+ assert self.state_group_before_event is not None
+ return await self._storage.state.get_state_ids_for_group(
+ self.state_group_before_event, state_filter
+ )
+
+ async def persist(self, event: EventBase) -> EventContext:
+ """
+ Creates a full `EventContext` for the event, persisting any referenced state that
+ has not yet been persisted.
+
+ Args:
+ event: event that the EventContext is associated with.
+
+ Returns: An EventContext suitable for sending to the database with the event
+ for persisting
+ """
+ assert self.partial_state is not None
+
+ # If we have a full set of state for before the event but don't have a state
+ # group for that state, we need to get one
+ if self.state_group_before_event is None:
+ assert self.state_map_before_event
+ state_group_before_event = await self._storage.state.store_state_group(
+ event.event_id,
+ event.room_id,
+ prev_group=self.prev_group_for_state_group_before_event,
+ delta_ids=self.delta_ids_to_state_group_before_event,
+ current_state_ids=self.state_map_before_event,
+ )
+ self.state_group_before_event = state_group_before_event
+
+ # if the event isn't a state event the state group doesn't change
+ if not self.state_delta_due_to_event:
+ state_group_after_event = self.state_group_before_event
+
+ # otherwise if it is a state event we need to get a state group for it
+ else:
+ state_group_after_event = await self._storage.state.store_state_group(
+ event.event_id,
+ event.room_id,
+ prev_group=self.state_group_before_event,
+ delta_ids=self.state_delta_due_to_event,
+ current_state_ids=None,
+ )
+
+ return EventContext.with_state(
+ storage=self._storage,
+ state_group=state_group_after_event,
+ state_group_before_event=self.state_group_before_event,
+ state_delta_due_to_event=self.state_delta_due_to_event,
+ partial_state=self.partial_state,
+ prev_group=self.state_group_before_event,
+ delta_ids=self.state_delta_due_to_event,
+ )
+
+
def _encode_state_dict(
state_dict: Optional[StateMap[str]],
) -> Optional[List[Tuple[str, str, str]]]:
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