Add support for persisting event format versions

Currently we only have the one event format version defined, but this
adds the necessary infrastructure to persist and fetch the format
versions alongside the events.

We specify the format version rather than the room version as:

1. We don't necessarily know the room version, existing events may be
   either v1 or v2.
2. We'd need to be careful to prevent/handle correctly if different
   events in the same room reported to be of different versions, which
   sounds annoying.

1 files changed, 15 insertions, 4 deletions

diff --git a/synapse/storage/events_worker.py b/synapse/storage/events_worker.py
index a8326f5296..8dff91e5f8 100644
--- a/synapse/storage/events_worker.py
+++ b/synapse/storage/events_worker.py
@@ -21,11 +21,11 @@ from canonicaljson import json
 
 from twisted.internet import defer
 
+from synapse.api.constants import EventFormatVersions
 from synapse.api.errors import NotFoundError
 # these are only included to make the type annotations work
-from synapse.events import EventBase  # noqa: F401
-from synapse.events import FrozenEvent
 from synapse.events.snapshot import EventContext  # noqa: F401
+from synapse.events import FrozenEvent
 from synapse.events.utils import prune_event
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.util.logcontext import (
@@ -353,6 +353,7 @@ class EventsWorkerStore(SQLBaseStore):
                     self._get_event_from_row,
                     row["internal_metadata"], row["json"], row["redacts"],
                     rejected_reason=row["rejects"],
+                    format_version=row["format_version"],
                 )
                 for row in rows
             ],
@@ -377,6 +378,7 @@ class EventsWorkerStore(SQLBaseStore):
                 " e.event_id as event_id, "
                 " e.internal_metadata,"
                 " e.json,"
+                " e.format_version, "
                 " r.redacts as redacts,"
                 " rej.event_id as rejects "
                 " FROM event_json as e"
@@ -392,7 +394,7 @@ class EventsWorkerStore(SQLBaseStore):
 
     @defer.inlineCallbacks
     def _get_event_from_row(self, internal_metadata, js, redacted,
-                            rejected_reason=None):
+                            format_version, rejected_reason=None):
         with Measure(self._clock, "_get_event_from_row"):
             d = json.loads(js)
             internal_metadata = json.loads(internal_metadata)
@@ -405,8 +407,17 @@ class EventsWorkerStore(SQLBaseStore):
                     desc="_get_event_from_row_rejected_reason",
                 )
 
+            if format_version is None:
+                # This means that we stored the event before we had the concept
+                # of a event format version, so it must be a V1 event.
+                format_version = EventFormatVersions.V1
+
+            # TODO: When we implement new event formats we'll need to use a
+            # different event python type
+            assert format_version == EventFormatVersions.V1
+
             original_ev = FrozenEvent(
-                d,
+                event_dict=d,
                 internal_metadata_dict=internal_metadata,
                 rejected_reason=rejected_reason,
             )