MM-41752: Batch update mention increment (#19596)

Previously, we were incrementing mentions one-by-one
all concurrently in an unbounded fashion.

This would cause a big spike in memory usage if there
were an `@all` mention in a large channel.

We fix this by changing the SQL query to take all userIDs
at once.

https://mattermost.atlassian.net/browse/MM-41752

```release-note
NONE
```

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

store/storetest/channel_store.go

@@ -4790,16 +4790,16 @@ func testChannelStoreIncrementMentionCount(t *testing.T, ss store.Store) {
 	_, err := ss.Channel().SaveMember(&m1)
 	require.NoError(t, err)
 
-	err = ss.Channel().IncrementMentionCount(m1.ChannelId, m1.UserId, false)
+	err = ss.Channel().IncrementMentionCount(m1.ChannelId, []string{m1.UserId}, false)
 	require.NoError(t, err, "failed to update")
 
-	err = ss.Channel().IncrementMentionCount(m1.ChannelId, "missing id", false)
+	err = ss.Channel().IncrementMentionCount(m1.ChannelId, []string{"missing id"}, false)
 	require.NoError(t, err, "failed to update")
 
-	err = ss.Channel().IncrementMentionCount("missing id", m1.UserId, false)
+	err = ss.Channel().IncrementMentionCount("missing id", []string{m1.UserId}, false)
 	require.NoError(t, err, "failed to update")
 
-	err = ss.Channel().IncrementMentionCount("missing id", "missing id", false)
+	err = ss.Channel().IncrementMentionCount("missing id", []string{"missing id"}, false)
 	require.NoError(t, err, "failed to update")
 }
 

store/storetest/mocks/ChannelStore.go

@@ -1508,13 +1508,13 @@ func (_m *ChannelStore) GroupSyncedChannelCount() (int64, error) {
 	return r0, r1
 }
 
-// IncrementMentionCount provides a mock function with given fields: channelID, userID, isRoot
-func (_m *ChannelStore) IncrementMentionCount(channelID string, userID string, isRoot bool) error {
-	ret := _m.Called(channelID, userID, isRoot)
+// IncrementMentionCount provides a mock function with given fields: channelID, userIDs, isRoot
+func (_m *ChannelStore) IncrementMentionCount(channelID string, userIDs []string, isRoot bool) error {
+	ret := _m.Called(channelID, userIDs, isRoot)
 
 	var r0 error
-	if rf, ok := ret.Get(0).(func(string, string, bool) error); ok {
-		r0 = rf(channelID, userID, isRoot)
+	if rf, ok := ret.Get(0).(func(string, []string, bool) error); ok {
+		r0 = rf(channelID, userIDs, isRoot)
 	} else {
 		r0 = ret.Error(0)
 	}

store/storetest/user_store.go

@@ -2285,6 +2285,15 @@ func testUserUnreadCount(t *testing.T, ss store.Store) {
 	_, nErr = ss.Team().SaveMember(&model.TeamMember{TeamId: teamId, UserId: u2.Id}, -1)
 	require.NoError(t, nErr)
 
+	u3 := &model.User{}
+	u3.Email = MakeEmail()
+	u3.Username = "user3" + model.NewId()
+	_, err = ss.User().Save(u3)
+	require.NoError(t, err)
+	defer func() { require.NoError(t, ss.User().PermanentDelete(u3.Id)) }()
+	_, nErr = ss.Team().SaveMember(&model.TeamMember{TeamId: teamId, UserId: u3.Id}, -1)
+	require.NoError(t, nErr)
+
 	_, nErr = ss.Channel().Save(&c1, -1)
 	require.NoError(t, nErr, "couldn't save item")
 
@@ -2301,6 +2310,14 @@ func testUserUnreadCount(t *testing.T, ss store.Store) {
 	_, nErr = ss.Channel().SaveMember(&m2)
 	require.NoError(t, nErr)
 
+	m3 := model.ChannelMember{}
+	m3.ChannelId = c1.Id
+	m3.UserId = u3.Id
+	m3.NotifyProps = model.GetDefaultChannelNotifyProps()
+
+	_, nErr = ss.Channel().SaveMember(&m3)
+	require.NoError(t, nErr)
+
 	m1.ChannelId = c2.Id
 	m2.ChannelId = c2.Id
 
@@ -2310,12 +2327,12 @@ func testUserUnreadCount(t *testing.T, ss store.Store) {
 	p1 := model.Post{}
 	p1.ChannelId = c1.Id
 	p1.UserId = u1.Id
-	p1.Message = "this is a message for @" + u2.Username
+	p1.Message = "this is a message for @" + u2.Username + " and " + "@" + u3.Username
 
 	// Post one message with mention to open channel
 	_, nErr = ss.Post().Save(&p1)
 	require.NoError(t, nErr)
-	nErr = ss.Channel().IncrementMentionCount(c1.Id, u2.Id, false)
+	nErr = ss.Channel().IncrementMentionCount(c1.Id, []string{u2.Id, u3.Id}, false)
 	require.NoError(t, nErr)
 
 	// Post 2 messages without mention to direct channel
@@ -2326,7 +2343,7 @@ func testUserUnreadCount(t *testing.T, ss store.Store) {
 
 	_, nErr = ss.Post().Save(&p2)
 	require.NoError(t, nErr)
-	nErr = ss.Channel().IncrementMentionCount(c2.Id, u2.Id, false)
+	nErr = ss.Channel().IncrementMentionCount(c2.Id, []string{u2.Id}, false)
 	require.NoError(t, nErr)
 
 	p3 := model.Post{}
@@ -2336,13 +2353,17 @@ func testUserUnreadCount(t *testing.T, ss store.Store) {
 	_, nErr = ss.Post().Save(&p3)
 	require.NoError(t, nErr)
 
-	nErr = ss.Channel().IncrementMentionCount(c2.Id, u2.Id, false)
+	nErr = ss.Channel().IncrementMentionCount(c2.Id, []string{u2.Id}, false)
 	require.NoError(t, nErr)
 
 	badge, unreadCountErr := ss.User().GetUnreadCount(u2.Id)
 	require.NoError(t, unreadCountErr)
 	require.Equal(t, int64(3), badge, "should have 3 unread messages")
 
+	badge, unreadCountErr = ss.User().GetUnreadCount(u3.Id)
+	require.NoError(t, unreadCountErr)
+	require.Equal(t, int64(1), badge, "should have 1 unread message")
+
 	badge, unreadCountErr = ss.User().GetUnreadCountForChannel(u2.Id, c1.Id)
 	require.NoError(t, unreadCountErr)
 	require.Equal(t, int64(1), badge, "should have 1 unread messages for that channel")