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| -rw-r--r-- | changelog.d/11469.doc | 1 | ||||
| -rw-r--r-- | docs/development/room-dag-concepts.md | 16 |
2 files changed, 8 insertions, 9 deletions
diff --git a/changelog.d/11469.doc b/changelog.d/11469.doc new file mode 100644 index 0000000000..51602aa968 --- /dev/null +++ b/changelog.d/11469.doc @@ -0,0 +1 @@ +Update section about backward extremities in the room DAG concepts doc to correct the misconception about backward extremities indicating whether we have fetched an events' `prev_events`. diff --git a/docs/development/room-dag-concepts.md b/docs/development/room-dag-concepts.md index 5eed72bec6..cbc7cf2949 100644 --- a/docs/development/room-dag-concepts.md +++ b/docs/development/room-dag-concepts.md @@ -38,16 +38,15 @@ Most-recent-in-time events in the DAG which are not referenced by any other even The forward extremities of a room are used as the `prev_events` when the next event is sent. -## Backwards extremity +## Backward extremity The current marker of where we have backfilled up to and will generally be the -oldest-in-time events we know of in the DAG. +`prev_events` of the oldest-in-time events we have in the DAG. This gives a starting point when +backfilling history. -This is an event where we haven't fetched all of the `prev_events` for. - -Once we have fetched all of its `prev_events`, it's unmarked as a backwards -extremity (although we may have formed new backwards extremities from the prev -events during the backfilling process). +When we persist a non-outlier event, we clear it as a backward extremity and set +all of its `prev_events` as the new backward extremities if they aren't already +persisted in the `events` table. ## Outliers @@ -56,8 +55,7 @@ We mark an event as an `outlier` when we haven't figured out the state for the room at that point in the DAG yet. We won't *necessarily* have the `prev_events` of an `outlier` in the database, -but it's entirely possible that we *might*. The status of whether we have all of -the `prev_events` is marked as a [backwards extremity](#backwards-extremity). +but it's entirely possible that we *might*. For example, when we fetch the event auth chain or state for a given event, we mark all of those claimed auth events as outliers because we haven't done the |