From 8f944f64349be6c434d5e47d9453c85db82d0144 Mon Sep 17 00:00:00 2001
From: Till <2353100+S7evinK@users.noreply.github.com>
Date: Tue, 20 Feb 2024 08:38:51 +0100
Subject: [PATCH] Limit filter to `limit/2` for before/after events on
 `/context` (#3332)

Part of https://github.com/matrix-org/dendrite/issues/3224
---
 syncapi/routing/context.go | 6 ++++++
 syncapi/syncapi_test.go    | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/syncapi/routing/context.go b/syncapi/routing/context.go
index b0c91c40..b136c69a 100644
--- a/syncapi/routing/context.go
+++ b/syncapi/routing/context.go
@@ -110,6 +110,7 @@ func Context(
 	}
 
 	stateFilter := synctypes.StateFilter{
+		Limit:                   filter.Limit,
 		NotSenders:              filter.NotSenders,
 		NotTypes:                filter.NotTypes,
 		Senders:                 filter.Senders,
@@ -157,6 +158,11 @@ func Context(
 		}
 	}
 
+	// Limit is split up for before/after events
+	if filter.Limit > 1 {
+		filter.Limit = filter.Limit / 2
+	}
+
 	eventsBefore, err := snapshot.SelectContextBeforeEvent(ctx, id, roomID, filter)
 	if err != nil && err != sql.ErrNoRows {
 		logrus.WithError(err).Error("unable to fetch before events")
diff --git a/syncapi/syncapi_test.go b/syncapi/syncapi_test.go
index 0a2c38ab..0392f209 100644
--- a/syncapi/syncapi_test.go
+++ b/syncapi/syncapi_test.go
@@ -1136,7 +1136,7 @@ func testContext(t *testing.T, dbType test.DBType) {
 		},
 		{
 			name:             "events are not limited",
-			wantBeforeLength: 7,
+			wantBeforeLength: 5,
 		},
 		{
 			name: "all events are limited",