Support very large channel membership lists (#11939)

Fixes the channel membership dialogue for the zed channel by not
downloading all 111k people in one go.

Release Notes:

- N/A

crates/collab/src/db/queries/buffers.rs

@@ -440,12 +440,7 @@ impl Database {
         channel_id: ChannelId,
         user: UserId,
         operations: &[proto::Operation],
-    ) -> Result<(
-        Vec<ConnectionId>,
-        Vec<UserId>,
-        i32,
-        Vec<proto::VectorClockEntry>,
-    )> {
+    ) -> Result<(HashSet<ConnectionId>, i32, Vec<proto::VectorClockEntry>)> {
         self.transaction(move |tx| async move {
             let channel = self.get_channel_internal(channel_id, &tx).await?;
 
@@ -479,7 +474,6 @@ impl Database {
                 .filter_map(|op| operation_to_storage(op, &buffer, serialization_version))
                 .collect::<Vec<_>>();
 
-            let mut channel_members;
             let max_version;
 
             if !operations.is_empty() {
@@ -504,12 +498,6 @@ impl Database {
                 )
                 .await?;
 
-                channel_members = self.get_channel_participants(&channel, &tx).await?;
-                let collaborators = self
-                    .get_channel_buffer_collaborators_internal(channel_id, &tx)
-                    .await?;
-                channel_members.retain(|member| !collaborators.contains(member));
-
                 buffer_operation::Entity::insert_many(operations)
                     .on_conflict(
                         OnConflict::columns([
@@ -524,11 +512,10 @@ impl Database {
                     .exec(&*tx)
                     .await?;
             } else {
-                channel_members = Vec::new();
                 max_version = Vec::new();
             }
 
-            let mut connections = Vec::new();
+            let mut connections = HashSet::default();
             let mut rows = channel_buffer_collaborator::Entity::find()
                 .filter(
                     Condition::all()
@@ -538,13 +525,13 @@ impl Database {
                 .await?;
             while let Some(row) = rows.next().await {
                 let row = row?;
-                connections.push(ConnectionId {
+                connections.insert(ConnectionId {
                     id: row.connection_id as u32,
                     owner_id: row.connection_server_id.0 as u32,
                 });
             }
 
-            Ok((connections, channel_members, buffer.epoch, max_version))
+            Ok((connections, buffer.epoch, max_version))
         })
         .await
     }