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| author | richvdh <richvdh@users.noreply.github.com> | 2022-09-27 19:44:10 +0000 |
|---|---|---|
| committer | richvdh <richvdh@users.noreply.github.com> | 2022-09-27 19:44:10 +0000 |
| commit | 9475d1aef0b2936bafbe28bad5692055353a7c08 (patch) | |
| tree | ef277f849496170f91f93f0a9b36f78386b5f782 /develop/print.html | |
| parent | deploy: 9bd442e202ce55966045820671c000aca25d6d6c (diff) | |
| download | synapse-9475d1aef0b2936bafbe28bad5692055353a7c08.tar.xz | |
deploy: 35e9d6a6161c05db491a36e8c194f9cb6b0af073
Diffstat (limited to 'develop/print.html')
| -rw-r--r-- | develop/print.html | 28 |
1 files changed, 14 insertions, 14 deletions
diff --git a/develop/print.html b/develop/print.html index e2549b6e1c..0a6eab1f9a 100644 --- a/develop/print.html +++ b/develop/print.html @@ -15380,21 +15380,21 @@ in Python, evaluates to <code>True</code>.</p> </li> </ul> <h2 id="event_id-global-uniqueness"><a class="header" href="#event_id-global-uniqueness"><code>event_id</code> global uniqueness</a></h2> -<p>In room versions <code>1</code> and <code>2</code> it's possible to end up with two events with the -same <code>event_id</code> (in the same or different rooms). After room version <code>3</code>, that -can only happen with a hash collision, which we basically hope will never -happen.</p> -<p>There are several places in Synapse and even Matrix APIs like <a href="https://spec.matrix.org/v1.1/server-server-api/#get_matrixfederationv1eventeventid"><code>GET /_matrix/federation/v1/event/{eventId}</code></a> -where we assume that event IDs are globally unique.</p> -<p>But hash collisions are still possible, and by treating event IDs as room -scoped, we can reduce the possibility of a hash collision. When scoping -<code>event_id</code> in the database schema, it should be also accompanied by <code>room_id</code> -(<code>PRIMARY KEY (room_id, event_id)</code>) and lookups should be done through the pair -<code>(room_id, event_id)</code>.</p> -<p>There has been a lot of debate on this in places like -https://github.com/matrix-org/matrix-spec-proposals/issues/2779 and +<p><code>event_id</code>'s can be considered globally unique although there has been a lot of +debate on this topic in places like +<a href="https://github.com/matrix-org/matrix-spec-proposals/issues/2779">MSC2779</a> and <a href="https://github.com/matrix-org/matrix-spec-proposals/pull/2848">MSC2848</a> which -has no resolution yet (as of 2022-09-01).</p> +has no resolution yet (as of 2022-09-01). There are several places in Synapse +and even in the Matrix APIs like <a href="https://spec.matrix.org/v1.1/server-server-api/#get_matrixfederationv1eventeventid"><code>GET /_matrix/federation/v1/event/{eventId}</code></a> +where we assume that event IDs are globally unique.</p> +<p>When scoping <code>event_id</code> in a database schema, it is often nice to accompany it +with <code>room_id</code> (<code>PRIMARY KEY (room_id, event_id)</code> and a <code>FOREIGN KEY(room_id) REFERENCES rooms(room_id)</code>) which makes flexible lookups easy. For example it +makes it very easy to find and clean up everything in a room when it needs to be +purged (no need to use sub-<code>select</code> query or join from the <code>events</code> table).</p> +<p>A note on collisions: In room versions <code>1</code> and <code>2</code> it's possible to end up with +two events with the same <code>event_id</code> (in the same or different rooms). After room +version <code>3</code>, that can only happen with a hash collision, which we basically hope +will never happen (SHA256 has a massive big key space).</p> <div style="break-before: page; page-break-before: always;"></div><h1 id="implementing-experimental-features-in-synapse"><a class="header" href="#implementing-experimental-features-in-synapse">Implementing experimental features in Synapse</a></h1> <p>It can be desirable to implement "experimental" features which are disabled by default and must be explicitly enabled via the Synapse configuration. This is |