Remove stream ordering from Metadata dict (#8452)

There's no need for it to be in the dict as well as the events table. Instead,
we store it in a separate attribute in the EventInternalMetadata object, and
populate that on load.

This means that we can rely on it being correctly populated for any event which
has been persited to the database.

1 files changed, 4 insertions, 2 deletions

diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py
index dc49df0812..7a51d0a22f 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -97,13 +97,16 @@ class DefaultDictProperty(DictProperty):
 
 
 class _EventInternalMetadata:
-    __slots__ = ["_dict"]
+    __slots__ = ["_dict", "stream_ordering"]
 
     def __init__(self, internal_metadata_dict: JsonDict):
         # we have to copy the dict, because it turns out that the same dict is
         # reused. TODO: fix that
         self._dict = dict(internal_metadata_dict)
 
+        # the stream ordering of this event. None, until it has been persisted.
+        self.stream_ordering = None  # type: Optional[int]
+
     outlier = DictProperty("outlier")  # type: bool
     out_of_band_membership = DictProperty("out_of_band_membership")  # type: bool
     send_on_behalf_of = DictProperty("send_on_behalf_of")  # type: str
@@ -113,7 +116,6 @@ class _EventInternalMetadata:
     redacted = DictProperty("redacted")  # type: bool
     txn_id = DictProperty("txn_id")  # type: str
     token_id = DictProperty("token_id")  # type: str
-    stream_ordering = DictProperty("stream_ordering")  # type: int
 
     # XXX: These are set by StreamWorkerStore._set_before_and_after.
     # I'm pretty sure that these are never persisted to the database, so shouldn't