finish implementing better state store

src/client_server/account.rs

@@ -249,6 +249,8 @@ pub async fn register_route(
 
         let room_id = RoomId::new(db.globals.server_name());
 
+        db.rooms.get_or_create_shortroomid(&room_id, &db.globals)?;
+
         let mutex_state = Arc::clone(
             db.globals
                 .roomid_mutex_state

src/client_server/context.rs

@@ -44,7 +44,7 @@ pub async fn get_context_route(
 
     let events_before = db
         .rooms
-        .pdus_until(&sender_user, &body.room_id, base_token)
+        .pdus_until(&sender_user, &body.room_id, base_token)?
         .take(
             u32::try_from(body.limit).map_err(|_| {
                 Error::BadRequest(ErrorKind::InvalidParam, "Limit value is invalid.")
@@ -66,7 +66,7 @@ pub async fn get_context_route(
 
     let events_after = db
         .rooms
-        .pdus_after(&sender_user, &body.room_id, base_token)
+        .pdus_after(&sender_user, &body.room_id, base_token)?
         .take(
             u32::try_from(body.limit).map_err(|_| {
                 Error::BadRequest(ErrorKind::InvalidParam, "Limit value is invalid.")

src/client_server/membership.rs

@@ -609,6 +609,8 @@ async fn join_room_by_id_helper(
             )
             .await?;
 
+        db.rooms.get_or_create_shortroomid(&room_id, &db.globals)?;
+
         let pdu = PduEvent::from_id_val(&event_id, join_event.clone())
             .map_err(|_| Error::BadServerResponse("Invalid join event PDU."))?;
 

src/client_server/message.rs

@@ -128,7 +128,7 @@ pub async fn get_message_events_route(
         get_message_events::Direction::Forward => {
             let events_after = db
                 .rooms
-                .pdus_after(&sender_user, &body.room_id, from)
+                .pdus_after(&sender_user, &body.room_id, from)?
                 .take(limit)
                 .filter_map(|r| r.ok()) // Filter out buggy events
                 .filter_map(|(pdu_id, pdu)| {
@@ -158,7 +158,7 @@ pub async fn get_message_events_route(
         get_message_events::Direction::Backward => {
             let events_before = db
                 .rooms
-                .pdus_until(&sender_user, &body.room_id, from)
+                .pdus_until(&sender_user, &body.room_id, from)?
                 .take(limit)
                 .filter_map(|r| r.ok()) // Filter out buggy events
                 .filter_map(|(pdu_id, pdu)| {

src/client_server/room.rs

@@ -33,6 +33,8 @@ pub async fn create_room_route(
 
     let room_id = RoomId::new(db.globals.server_name());
 
+    db.rooms.get_or_create_shortroomid(&room_id, &db.globals)?;
+
     let mutex_state = Arc::clone(
         db.globals
             .roomid_mutex_state
@@ -173,7 +175,6 @@ pub async fn create_room_route(
     )?;
 
     // 4. Canonical room alias
-
     if let Some(room_alias_id) = &alias {
         db.rooms.build_and_append_pdu(
             PduBuilder {
@@ -193,7 +194,7 @@ pub async fn create_room_route(
             &room_id,
             &db,
             &state_lock,
-        );
+        )?;
     }
 
     // 5. Events set by preset

src/client_server/sync.rs

@@ -205,7 +205,7 @@ async fn sync_helper(
 
         let mut non_timeline_pdus = db
             .rooms
-            .pdus_until(&sender_user, &room_id, u64::MAX)
+            .pdus_until(&sender_user, &room_id, u64::MAX)?
             .filter_map(|r| {
                 // Filter out buggy events
                 if r.is_err() {
@@ -248,13 +248,13 @@ async fn sync_helper(
 
         let first_pdu_before_since = db
             .rooms
-            .pdus_until(&sender_user, &room_id, since)
+            .pdus_until(&sender_user, &room_id, since)?
             .next()
             .transpose()?;
 
         let pdus_after_since = db
             .rooms
-            .pdus_after(&sender_user, &room_id, since)
+            .pdus_after(&sender_user, &room_id, since)?
             .next()
             .is_some();
 
@@ -286,7 +286,7 @@ async fn sync_helper(
 
                 for hero in db
                     .rooms
-                    .all_pdus(&sender_user, &room_id)
+                    .all_pdus(&sender_user, &room_id)?
                     .filter_map(|pdu| pdu.ok()) // Ignore all broken pdus
                     .filter(|(_, pdu)| pdu.kind == EventType::RoomMember)
                     .map(|(_, pdu)| {
@@ -328,11 +328,11 @@ async fn sync_helper(
                 }
             }
 
-            (
+            Ok::<_, Error>((
                 Some(joined_member_count),
                 Some(invited_member_count),
                 heroes,
-            )
+            ))
         };
 
         let (
@@ -343,7 +343,7 @@ async fn sync_helper(
             state_events,
         ) = if since_shortstatehash.is_none() {
             // Probably since = 0, we will do an initial sync
-            let (joined_member_count, invited_member_count, heroes) = calculate_counts();
+            let (joined_member_count, invited_member_count, heroes) = calculate_counts()?;
 
             let current_state_ids = db.rooms.state_full_ids(current_shortstatehash)?;
             let state_events = current_state_ids
@@ -510,7 +510,7 @@ async fn sync_helper(
             }
 
             let (joined_member_count, invited_member_count, heroes) = if send_member_count {
-                calculate_counts()
+                calculate_counts()?
             } else {
                 (None, None, Vec::new())
             };

src/database.rs

@@ -28,7 +28,7 @@ use ruma::{DeviceId, EventId, RoomId, ServerName, UserId};
 use serde::{de::IgnoredAny, Deserialize};
 use std::{
     collections::{BTreeMap, HashMap, HashSet},
-    convert::TryFrom,
+    convert::{TryFrom, TryInto},
     fs::{self, remove_dir_all},
     io::Write,
     mem::size_of,
@@ -266,7 +266,6 @@ impl Database {
                 shortroomid_roomid: builder.open_tree("shortroomid_roomid")?,
                 roomid_shortroomid: builder.open_tree("roomid_shortroomid")?,
 
-                stateid_shorteventid: builder.open_tree("stateid_shorteventid")?,
                 shortstatehash_statediff: builder.open_tree("shortstatehash_statediff")?,
                 eventid_shorteventid: builder.open_tree("eventid_shorteventid")?,
                 shorteventid_eventid: builder.open_tree("shorteventid_eventid")?,
@@ -431,7 +430,6 @@ impl Database {
             }
 
             if db.globals.database_version()? < 6 {
-                // TODO update to 6
                 // Set room member count
                 for (roomid, _) in db.rooms.roomid_shortstatehash.iter() {
                     let room_id =
@@ -445,207 +443,27 @@ impl Database {
                 println!("Migration: 5 -> 6 finished");
             }
 
-            fn load_shortstatehash_info(
-                shortstatehash: &[u8],
-                db: &Database,
-                lru: &mut LruCache<
-                    Vec<u8>,
-                    Vec<(
-                        Vec<u8>,
-                        HashSet<Vec<u8>>,
-                        HashSet<Vec<u8>>,
-                        HashSet<Vec<u8>>,
-                    )>,
-                >,
-            ) -> Result<
-                Vec<(
-                    Vec<u8>,          // sstatehash
-                    HashSet<Vec<u8>>, // full state
-                    HashSet<Vec<u8>>, // added
-                    HashSet<Vec<u8>>, // removed
-                )>,
-            > {
-                if let Some(result) = lru.get_mut(shortstatehash) {
-                    return Ok(result.clone());
-                }
-
-                let value = db
-                    .rooms
-                    .shortstatehash_statediff
-                    .get(shortstatehash)?
-                    .ok_or_else(|| Error::bad_database("State hash does not exist"))?;
-                let parent = value[0..size_of::<u64>()].to_vec();
-
-                let mut add_mode = true;
-                let mut added = HashSet::new();
-                let mut removed = HashSet::new();
-
-                let mut i = size_of::<u64>();
-                while let Some(v) = value.get(i..i + 2 * size_of::<u64>()) {
-                    if add_mode && v.starts_with(&0_u64.to_be_bytes()) {
-                        add_mode = false;
-                        i += size_of::<u64>();
-                        continue;
-                    }
-                    if add_mode {
-                        added.insert(v.to_vec());
-                    } else {
-                        removed.insert(v.to_vec());
-                    }
-                    i += 2 * size_of::<u64>();
-                }
-
-                if parent != 0_u64.to_be_bytes() {
-                    let mut response = load_shortstatehash_info(&parent, db, lru)?;
-                    let mut state = response.last().unwrap().1.clone();
-                    state.extend(added.iter().cloned());
-                    for r in &removed {
-                        state.remove(r);
-                    }
-
-                    response.push((shortstatehash.to_vec(), state, added, removed));
-
-                    lru.insert(shortstatehash.to_vec(), response.clone());
-                    Ok(response)
-                } else {
-                    let mut response = Vec::new();
-                    response.push((shortstatehash.to_vec(), added.clone(), added, removed));
-                    lru.insert(shortstatehash.to_vec(), response.clone());
-                    Ok(response)
-                }
-            }
-
-            fn update_shortstatehash_level(
-                current_shortstatehash: &[u8],
-                statediffnew: HashSet<Vec<u8>>,
-                statediffremoved: HashSet<Vec<u8>>,
-                diff_to_sibling: usize,
-                mut parent_states: Vec<(
-                    Vec<u8>,          // sstatehash
-                    HashSet<Vec<u8>>, // full state
-                    HashSet<Vec<u8>>, // added
-                    HashSet<Vec<u8>>, // removed
-                )>,
-                db: &Database,
-            ) -> Result<()> {
-                let diffsum = statediffnew.len() + statediffremoved.len();
-
-                if parent_states.len() > 3 {
-                    // Number of layers
-                    // To many layers, we have to go deeper
-                    let parent = parent_states.pop().unwrap();
-
-                    let mut parent_new = parent.2;
-                    let mut parent_removed = parent.3;
-
-                    for removed in statediffremoved {
-                        if !parent_new.remove(&removed) {
-                            parent_removed.insert(removed);
-                        }
-                    }
-                    parent_new.extend(statediffnew);
-
-                    update_shortstatehash_level(
-                        current_shortstatehash,
-                        parent_new,
-                        parent_removed,
-                        diffsum,
-                        parent_states,
-                        db,
-                    )?;
-
-                    return Ok(());
-                }
-
-                if parent_states.len() == 0 {
-                    // There is no parent layer, create a new state
-                    let mut value = 0_u64.to_be_bytes().to_vec(); // 0 means no parent
-                    for new in &statediffnew {
-                        value.extend_from_slice(&new);
-                    }
-
-                    if !statediffremoved.is_empty() {
-                        warn!("Tried to create new state with removals");
-                    }
-
-                    db.rooms
-                        .shortstatehash_statediff
-                        .insert(&current_shortstatehash, &value)?;
-
-                    return Ok(());
-                };
-
-                // Else we have two options.
-                // 1. We add the current diff on top of the parent layer.
-                // 2. We replace a layer above
-
-                let parent = parent_states.pop().unwrap();
-                let parent_diff = parent.2.len() + parent.3.len();
-
-                if diffsum * diffsum >= 2 * diff_to_sibling * parent_diff {
-                    // Diff too big, we replace above layer(s)
-                    let mut parent_new = parent.2;
-                    let mut parent_removed = parent.3;
-
-                    for removed in statediffremoved {
-                        if !parent_new.remove(&removed) {
-                            parent_removed.insert(removed);
-                        }
-                    }
-
-                    parent_new.extend(statediffnew);
-                    update_shortstatehash_level(
-                        current_shortstatehash,
-                        parent_new,
-                        parent_removed,
-                        diffsum,
-                        parent_states,
-                        db,
-                    )?;
-                } else {
-                    // Diff small enough, we add diff as layer on top of parent
-                    let mut value = parent.0.clone();
-                    for new in &statediffnew {
-                        value.extend_from_slice(&new);
-                    }
-
-                    if !statediffremoved.is_empty() {
-                        value.extend_from_slice(&0_u64.to_be_bytes());
-                        for removed in &statediffremoved {
-                            value.extend_from_slice(&removed);
-                        }
-                    }
-
-                    db.rooms
-                        .shortstatehash_statediff
-                        .insert(&current_shortstatehash, &value)?;
-                }
-
-                Ok(())
-            }
-
             if db.globals.database_version()? < 7 {
                 // Upgrade state store
-                let mut lru = LruCache::new(1000);
+                let mut last_roomstates: HashMap<RoomId, u64> = HashMap::new();
-                let mut last_roomstates: HashMap<RoomId, Vec<u8>> = HashMap::new();
+                let mut current_sstatehash: Option<u64> = None;
-                let mut current_sstatehash: Vec<u8> = Vec::new();
                 let mut current_room = None;
                 let mut current_state = HashSet::new();
                 let mut counter = 0;
-                for (k, seventid) in db._db.open_tree("stateid_shorteventid")?.iter() {
+
-                    let sstatehash = k[0..size_of::<u64>()].to_vec();
+                let mut handle_state =
-                    let sstatekey = k[size_of::<u64>()..].to_vec();
+                    |current_sstatehash: u64,
-                    if sstatehash != current_sstatehash {
+                     current_room: &RoomId,
-                        if !current_sstatehash.is_empty() {
+                     current_state: HashSet<_>,
+                     last_roomstates: &mut HashMap<_, _>| {
                         counter += 1;
                         println!("counter: {}", counter);
-                            let current_room = current_room.as_ref().unwrap();
+                        let last_roomsstatehash = last_roomstates.get(current_room);
-                            let last_roomsstatehash = last_roomstates.get(&current_room);
 
                         let states_parents = last_roomsstatehash.map_or_else(
                             || Ok(Vec::new()),
-                                |last_roomsstatehash| {
+                            |&last_roomsstatehash| {
-                                    load_shortstatehash_info(&last_roomsstatehash, &db, &mut lru)
+                                db.rooms.load_shortstatehash_info(dbg!(last_roomsstatehash))
                             },
                         )?;
 
@@ -667,17 +485,16 @@ impl Database {
                                 (current_state, HashSet::new())
                             };
 
-                            update_shortstatehash_level(
+                        db.rooms.save_state_from_diff(
-                                &current_sstatehash,
+                            dbg!(current_sstatehash),
                             statediffnew,
                             statediffremoved,
                             2, // every state change is 2 event changes on average
                             states_parents,
-                                &db,
                         )?;
 
                         /*
-                            let mut tmp = load_shortstatehash_info(&current_sstatehash, &db)?;
+                        let mut tmp = db.rooms.load_shortstatehash_info(&current_sstatehash, &db)?;
                         let state = tmp.pop().unwrap();
                         println!(
                             "{}\t{}{:?}: {:?} + {:?} - {:?}",
@@ -698,10 +515,26 @@ impl Database {
                         );
                         */
 
-                            last_roomstates.insert(current_room.clone(), current_sstatehash);
+                        Ok::<_, Error>(())
+                    };
+
+                for (k, seventid) in db._db.open_tree("stateid_shorteventid")?.iter() {
+                    let sstatehash = utils::u64_from_bytes(&k[0..size_of::<u64>()])
+                        .expect("number of bytes is correct");
+                    let sstatekey = k[size_of::<u64>()..].to_vec();
+                    if Some(sstatehash) != current_sstatehash {
+                        if let Some(current_sstatehash) = current_sstatehash {
+                            handle_state(
+                                current_sstatehash,
+                                current_room.as_ref().unwrap(),
+                                current_state,
+                                &mut last_roomstates,
+                            )?;
+                            last_roomstates
+                                .insert(current_room.clone().unwrap(), current_sstatehash);
                         }
                         current_state = HashSet::new();
-                        current_sstatehash = sstatehash;
+                        current_sstatehash = Some(sstatehash);
 
                         let event_id = db
                             .rooms
@@ -721,7 +554,16 @@ impl Database {
 
                     let mut val = sstatekey;
                     val.extend_from_slice(&seventid);
-                    current_state.insert(val);
+                    current_state.insert(val.try_into().expect("size is correct"));
+                }
+
+                if let Some(current_sstatehash) = current_sstatehash {
+                    handle_state(
+                        current_sstatehash,
+                        current_room.as_ref().unwrap(),
+                        current_state,
+                        &mut last_roomstates,
+                    )?;
                 }
 
                 db.globals.bump_database_version(7)?;
@@ -761,11 +603,28 @@ impl Database {
 
                 db.rooms.pduid_pdu.insert_batch(&mut batch)?;
 
-                for (key, _) in db.rooms.pduid_pdu.iter() {
+                let mut batch2 = db.rooms.eventid_pduid.iter().filter_map(|(k, value)| {
-                    if key.starts_with(b"!") {
+                    if !value.starts_with(b"!") {
-                        db.rooms.pduid_pdu.remove(&key);
+                        return None;
-                    }
                     }
+                    let mut parts = value.splitn(2, |&b| b == 0xff);
+                    let room_id = parts.next().unwrap();
+                    let count = parts.next().unwrap();
+
+                    let short_room_id = db
+                        .rooms
+                        .roomid_shortroomid
+                        .get(&room_id)
+                        .unwrap()
+                        .expect("shortroomid should exist");
+
+                    let mut new_value = short_room_id;
+                    new_value.extend_from_slice(count);
+
+                    Some((k, new_value))
+                });
+
+                db.rooms.eventid_pduid.insert_batch(&mut batch2)?;
 
                 db.globals.bump_database_version(8)?;
 
@@ -803,7 +662,7 @@ impl Database {
 
                 for (key, _) in db.rooms.tokenids.iter() {
                     if key.starts_with(b"!") {
-                        db.rooms.pduid_pdu.remove(&key)?;
+                        db.rooms.tokenids.remove(&key)?;
                     }
                 }
 
@@ -811,8 +670,6 @@ impl Database {
 
                 println!("Migration: 8 -> 9 finished");
             }
-
-            panic!();
         }
 
         let guard = db.read().await;

src/database/abstraction/sqlite.rs

@@ -9,13 +9,13 @@ use std::{
     path::{Path, PathBuf},
     pin::Pin,
     sync::Arc,
-    time::{Duration, Instant},
 };
 use tokio::sync::oneshot::Sender;
 use tracing::debug;
 
 thread_local! {
     static READ_CONNECTION: RefCell<Option<&'static Connection>> = RefCell::new(None);
+    static READ_CONNECTION_ITERATOR: RefCell<Option<&'static Connection>> = RefCell::new(None);
 }
 
 struct PreparedStatementIterator<'a> {
@@ -77,6 +77,21 @@ impl Engine {
         })
     }
 
+    fn read_lock_iterator(&self) -> &'static Connection {
+        READ_CONNECTION_ITERATOR.with(|cell| {
+            let connection = &mut cell.borrow_mut();
+
+            if (*connection).is_none() {
+                let c = Box::leak(Box::new(
+                    Self::prepare_conn(&self.path, self.cache_size_per_thread).unwrap(),
+                ));
+                **connection = Some(c);
+            }
+
+            connection.unwrap()
+        })
+    }
+
     pub fn flush_wal(self: &Arc<Self>) -> Result<()> {
         self.write_lock()
             .pragma_update(Some(Main), "wal_checkpoint", &"TRUNCATE")?;
@@ -151,6 +166,34 @@ impl SqliteTable {
         )?;
         Ok(())
     }
+
+    pub fn iter_with_guard<'a>(
+        &'a self,
+        guard: &'a Connection,
+    ) -> Box<dyn Iterator<Item = TupleOfBytes> + 'a> {
+        let statement = Box::leak(Box::new(
+            guard
+                .prepare(&format!(
+                    "SELECT key, value FROM {} ORDER BY key ASC",
+                    &self.name
+                ))
+                .unwrap(),
+        ));
+
+        let statement_ref = NonAliasingBox(statement);
+
+        let iterator = Box::new(
+            statement
+                .query_map([], |row| Ok((row.get_unwrap(0), row.get_unwrap(1))))
+                .unwrap()
+                .map(|r| r.unwrap()),
+        );
+
+        Box::new(PreparedStatementIterator {
+            iterator,
+            statement_ref,
+        })
+    }
 }
 
 impl Tree for SqliteTable {
@@ -219,30 +262,9 @@ impl Tree for SqliteTable {
 
     #[tracing::instrument(skip(self))]
     fn iter<'a>(&'a self) -> Box<dyn Iterator<Item = TupleOfBytes> + 'a> {
-        let guard = self.engine.read_lock();
+        let guard = self.engine.read_lock_iterator();
 
-        let statement = Box::leak(Box::new(
+        self.iter_with_guard(&guard)
-            guard
-                .prepare(&format!(
-                    "SELECT key, value FROM {} ORDER BY key ASC",
-                    &self.name
-                ))
-                .unwrap(),
-        ));
-
-        let statement_ref = NonAliasingBox(statement);
-
-        let iterator = Box::new(
-            statement
-                .query_map([], |row| Ok((row.get_unwrap(0), row.get_unwrap(1))))
-                .unwrap()
-                .map(|r| r.unwrap()),
-        );
-
-        Box::new(PreparedStatementIterator {
-            iterator,
-            statement_ref,
-        })
     }
 
     #[tracing::instrument(skip(self, from, backwards))]
@@ -251,7 +273,7 @@ impl Tree for SqliteTable {
         from: &[u8],
         backwards: bool,
     ) -> Box<dyn Iterator<Item = TupleOfBytes> + 'a> {
-        let guard = self.engine.read_lock();
+        let guard = self.engine.read_lock_iterator();
         let from = from.to_vec(); // TODO change interface?
 
         if backwards {

src/database/rooms.rs

@@ -24,7 +24,7 @@ use ruma::{
 use std::{
     collections::{BTreeMap, BTreeSet, HashMap, HashSet},
     convert::{TryFrom, TryInto},
-    mem,
+    mem::size_of,
     sync::{Arc, Mutex},
 };
 use tokio::sync::MutexGuard;
@@ -37,10 +37,11 @@ use super::{abstraction::Tree, admin::AdminCommand, pusher};
 /// This is created when a state group is added to the database by
 /// hashing the entire state.
 pub type StateHashId = Vec<u8>;
+pub type CompressedStateEvent = [u8; 2 * size_of::<u64>()];
 
 pub struct Rooms {
     pub edus: edus::RoomEdus,
-    pub(super) pduid_pdu: Arc<dyn Tree>, // PduId = RoomId + Count
+    pub(super) pduid_pdu: Arc<dyn Tree>, // PduId = ShortRoomId + Count
     pub(super) eventid_pduid: Arc<dyn Tree>,
     pub(super) roomid_pduleaves: Arc<dyn Tree>,
     pub(super) alias_roomid: Arc<dyn Tree>,
@@ -79,9 +80,6 @@ pub struct Rooms {
     pub(super) eventid_shorteventid: Arc<dyn Tree>,
 
     pub(super) statehash_shortstatehash: Arc<dyn Tree>,
-    /// ShortStateHash = Count
-    /// StateId = ShortStateHash
-    pub(super) stateid_shorteventid: Arc<dyn Tree>,
     pub(super) shortstatehash_statediff: Arc<dyn Tree>, // StateDiff = parent (or 0) + (shortstatekey+shorteventid++) + 0_u64 + (shortstatekey+shorteventid--)
 
     /// RoomId + EventId -> outlier PDU.
@@ -100,29 +98,30 @@ impl Rooms {
     /// Builds a StateMap by iterating over all keys that start
     /// with state_hash, this gives the full state for the given state_hash.
     pub fn state_full_ids(&self, shortstatehash: u64) -> Result<BTreeSet<EventId>> {
-        Ok(self
+        let full_state = self
-            .stateid_shorteventid
+            .load_shortstatehash_info(shortstatehash)?
-            .scan_prefix(shortstatehash.to_be_bytes().to_vec())
+            .pop()
-            .map(|(_, bytes)| {
+            .expect("there is always one layer")
-                self.get_eventid_from_short(utils::u64_from_bytes(&bytes).unwrap())
+            .1;
-                    .ok()
+        full_state
-            })
+            .into_iter()
-            .flatten()
+            .map(|compressed| self.parse_compressed_state_event(compressed))
-            .collect())
+            .collect()
     }
 
     pub fn state_full(
         &self,
         shortstatehash: u64,
     ) -> Result<HashMap<(EventType, String), Arc<PduEvent>>> {
-        let state = self
+        let full_state = self
-            .stateid_shorteventid
+            .load_shortstatehash_info(shortstatehash)?
-            .scan_prefix(shortstatehash.to_be_bytes().to_vec())
+            .pop()
-            .map(|(_, bytes)| {
+            .expect("there is always one layer")
-                self.get_eventid_from_short(utils::u64_from_bytes(&bytes).unwrap())
+            .1;
-                    .ok()
+        Ok(full_state
-            })
+            .into_iter()
-            .flatten()
+            .map(|compressed| self.parse_compressed_state_event(compressed))
+            .filter_map(|r| r.ok())
             .map(|eventid| self.get_pdu(&eventid))
             .filter_map(|r| r.ok().flatten())
             .map(|pdu| {
@@ -138,9 +137,7 @@ impl Rooms {
                 ))
             })
             .filter_map(|r| r.ok())
-            .collect();
+            .collect())
-
-        Ok(state)
     }
 
     /// Returns a single PDU from `room_id` with key (`event_type`, `state_key`).
@@ -151,27 +148,19 @@ impl Rooms {
         event_type: &EventType,
         state_key: &str,
     ) -> Result<Option<EventId>> {
-        let mut key = event_type.as_ref().as_bytes().to_vec();
+        let shortstatekey = match self.get_shortstatekey(event_type, state_key)? {
-        key.push(0xff);
+            Some(s) => s,
-        key.extend_from_slice(&state_key.as_bytes());
+            None => return Ok(None),
-
+        };
-        let shortstatekey = self.statekey_shortstatekey.get(&key)?;
+        let full_state = self
-
+            .load_shortstatehash_info(shortstatehash)?
-        if let Some(shortstatekey) = shortstatekey {
+            .pop()
-            let mut stateid = shortstatehash.to_be_bytes().to_vec();
+            .expect("there is always one layer")
-            stateid.extend_from_slice(&shortstatekey);
+            .1;
-
+        Ok(full_state
-            Ok(self
+            .into_iter()
-                .stateid_shorteventid
+            .find(|bytes| bytes.starts_with(&shortstatekey.to_be_bytes()))
-                .get(&stateid)?
+            .and_then(|compressed| self.parse_compressed_state_event(compressed).ok()))
-                .map(|bytes| {
-                    self.get_eventid_from_short(utils::u64_from_bytes(&bytes).unwrap())
-                        .ok()
-                })
-                .flatten())
-        } else {
-            Ok(None)
-        }
     }
 
     /// Returns a single PDU from `room_id` with key (`event_type`, `state_key`).
@@ -260,8 +249,7 @@ impl Rooms {
 
     /// Checks if a room exists.
     pub fn exists(&self, room_id: &RoomId) -> Result<bool> {
-        let mut prefix = room_id.as_bytes().to_vec();
+        let prefix = self.get_shortroomid(room_id)?.to_be_bytes().to_vec();
-        prefix.push(0xff);
 
         // Look for PDUs in that room.
         Ok(self
@@ -274,8 +262,7 @@ impl Rooms {
 
     /// Checks if a room exists.
     pub fn first_pdu_in_room(&self, room_id: &RoomId) -> Result<Option<Arc<PduEvent>>> {
-        let mut prefix = room_id.as_bytes().to_vec();
+        let prefix = self.get_shortroomid(room_id)?.to_be_bytes().to_vec();
-        prefix.push(0xff);
 
         // Look for PDUs in that room.
         self.pduid_pdu
@@ -292,74 +279,78 @@ impl Rooms {
 
     /// Force the creation of a new StateHash and insert it into the db.
     ///
-    /// Whatever `state` is supplied to `force_state` __is__ the current room state snapshot.
+    /// Whatever `state` is supplied to `force_state` becomes the new current room state snapshot.
     pub fn force_state(
         &self,
         room_id: &RoomId,
-        state: HashMap<(EventType, String), EventId>,
+        new_state: HashMap<(EventType, String), EventId>,
         db: &Database,
     ) -> Result<()> {
+        let previous_shortstatehash = self.current_shortstatehash(&room_id)?;
+
+        let new_state_ids_compressed = new_state
+            .iter()
+            .filter_map(|((event_type, state_key), event_id)| {
+                let shortstatekey = self
+                    .get_or_create_shortstatekey(event_type, state_key, &db.globals)
+                    .ok()?;
+                Some(
+                    self.compress_state_event(shortstatekey, event_id, &db.globals)
+                        .ok()?,
+                )
+            })
+            .collect::<HashSet<_>>();
+
         let state_hash = self.calculate_hash(
-            &state
+            &new_state
                 .values()
                 .map(|event_id| event_id.as_bytes())
                 .collect::<Vec<_>>(),
         );
 
-        let (shortstatehash, already_existed) =
+        let (new_shortstatehash, already_existed) =
             self.get_or_create_shortstatehash(&state_hash, &db.globals)?;
 
-        let new_state = if !already_existed {
+        if Some(new_shortstatehash) == previous_shortstatehash {
-            let mut new_state = HashSet::new();
+            return Ok(());
-
-            let batch = state
-                .iter()
-                .filter_map(|((event_type, state_key), eventid)| {
-                    new_state.insert(eventid.clone());
-
-                    let mut statekey = event_type.as_ref().as_bytes().to_vec();
-                    statekey.push(0xff);
-                    statekey.extend_from_slice(&state_key.as_bytes());
-
-                    let shortstatekey = match self.statekey_shortstatekey.get(&statekey).ok()? {
-                        Some(shortstatekey) => shortstatekey.to_vec(),
-                        None => {
-                            let shortstatekey = db.globals.next_count().ok()?;
-                            self.statekey_shortstatekey
-                                .insert(&statekey, &shortstatekey.to_be_bytes())
-                                .ok()?;
-                            shortstatekey.to_be_bytes().to_vec()
         }
-                    };
 
-                    let shorteventid = self
+        let states_parents = previous_shortstatehash
-                        .get_or_create_shorteventid(&eventid, &db.globals)
+            .map_or_else(|| Ok(Vec::new()), |p| self.load_shortstatehash_info(p))?;
-                        .ok()?;
 
-                    let mut state_id = shortstatehash.to_be_bytes().to_vec();
+        let (statediffnew, statediffremoved) = if let Some(parent_stateinfo) = states_parents.last()
-                    state_id.extend_from_slice(&shortstatekey);
+        {
+            let statediffnew = new_state_ids_compressed
+                .difference(&parent_stateinfo.1)
+                .cloned()
+                .collect::<HashSet<_>>();
 
-                    Some((state_id, shorteventid.to_be_bytes().to_vec()))
+            let statediffremoved = parent_stateinfo
-                })
+                .1
-                .collect::<Vec<_>>();
+                .difference(&new_state_ids_compressed)
+                .cloned()
+                .collect::<HashSet<_>>();
 
-            self.stateid_shorteventid
+            (statediffnew, statediffremoved)
-                .insert_batch(&mut batch.into_iter())?;
-
-            new_state
         } else {
-            self.state_full_ids(shortstatehash)?.into_iter().collect()
+            (new_state_ids_compressed, HashSet::new())
         };
 
-        let old_state = self
+        if !already_existed {
-            .current_shortstatehash(&room_id)?
+            self.save_state_from_diff(
-            .map(|s| self.state_full_ids(s))
+                new_shortstatehash,
-            .transpose()?
+                statediffnew.clone(),
-            .map(|vec| vec.into_iter().collect::<HashSet<_>>())
+                statediffremoved.clone(),
-            .unwrap_or_default();
+                2, // every state change is 2 event changes on average
+                states_parents,
+            )?;
+        };
 
-        for event_id in new_state.difference(&old_state) {
+        for event_id in statediffnew
-            if let Some(pdu) = self.get_pdu_json(event_id)? {
+            .into_iter()
+            .filter_map(|new| self.parse_compressed_state_event(new).ok())
+        {
+            if let Some(pdu) = self.get_pdu_json(&event_id)? {
                 if pdu.get("type").and_then(|val| val.as_str()) == Some("m.room.member") {
                     if let Ok(pdu) = serde_json::from_value::<PduEvent>(
                         serde_json::to_value(&pdu).expect("CanonicalJsonObj is a valid JsonValue"),
@@ -392,7 +383,206 @@ impl Rooms {
         }
 
         self.roomid_shortstatehash
-            .insert(room_id.as_bytes(), &shortstatehash.to_be_bytes())?;
+            .insert(room_id.as_bytes(), &new_shortstatehash.to_be_bytes())?;
+
+        Ok(())
+    }
+
+    /// Returns a stack with info on shortstatehash, full state, added diff and removed diff for the selected shortstatehash and each parent layer.
+    pub fn load_shortstatehash_info(
+        &self,
+        shortstatehash: u64,
+    ) -> Result<
+        Vec<(
+            u64,                           // sstatehash
+            HashSet<CompressedStateEvent>, // full state
+            HashSet<CompressedStateEvent>, // added
+            HashSet<CompressedStateEvent>, // removed
+        )>,
+    > {
+        let value = self
+            .shortstatehash_statediff
+            .get(&shortstatehash.to_be_bytes())?
+            .ok_or_else(|| Error::bad_database("State hash does not exist"))?;
+        let parent =
+            utils::u64_from_bytes(&value[0..size_of::<u64>()]).expect("bytes have right length");
+
+        let mut add_mode = true;
+        let mut added = HashSet::new();
+        let mut removed = HashSet::new();
+
+        let mut i = size_of::<u64>();
+        while let Some(v) = value.get(i..i + 2 * size_of::<u64>()) {
+            if add_mode && v.starts_with(&0_u64.to_be_bytes()) {
+                add_mode = false;
+                i += size_of::<u64>();
+                continue;
+            }
+            if add_mode {
+                added.insert(v.try_into().expect("we checked the size above"));
+            } else {
+                removed.insert(v.try_into().expect("we checked the size above"));
+            }
+            i += 2 * size_of::<u64>();
+        }
+
+        if parent != 0_u64 {
+            let mut response = self.load_shortstatehash_info(parent)?;
+            let mut state = response.last().unwrap().1.clone();
+            state.extend(added.iter().cloned());
+            for r in &removed {
+                state.remove(r);
+            }
+
+            response.push((shortstatehash, state, added, removed));
+
+            Ok(response)
+        } else {
+            let mut response = Vec::new();
+            response.push((shortstatehash, added.clone(), added, removed));
+            Ok(response)
+        }
+    }
+
+    pub fn compress_state_event(
+        &self,
+        shortstatekey: u64,
+        event_id: &EventId,
+        globals: &super::globals::Globals,
+    ) -> Result<CompressedStateEvent> {
+        let mut v = shortstatekey.to_be_bytes().to_vec();
+        v.extend_from_slice(
+            &self
+                .get_or_create_shorteventid(event_id, globals)?
+                .to_be_bytes(),
+        );
+        Ok(v.try_into().expect("we checked the size above"))
+    }
+
+    pub fn parse_compressed_state_event(
+        &self,
+        compressed_event: CompressedStateEvent,
+    ) -> Result<EventId> {
+        self.get_eventid_from_short(
+            utils::u64_from_bytes(&compressed_event[size_of::<u64>()..])
+                .expect("bytes have right length"),
+        )
+    }
+
+    /// Creates a new shortstatehash that often is just a diff to an already existing
+    /// shortstatehash and therefore very efficient.
+    ///
+    /// There are multiple layers of diffs. The bottom layer 0 always contains the full state. Layer
+    /// 1 contains diffs to states of layer 0, layer 2 diffs to layer 1 and so on. If layer n > 0
+    /// grows too big, it will be combined with layer n-1 to create a new diff on layer n-1 that's
+    /// based on layer n-2. If that layer is also too big, it will recursively fix above layers too.
+    ///
+    /// * `shortstatehash` - Shortstatehash of this state
+    /// * `statediffnew` - Added to base. Each vec is shortstatekey+shorteventid
+    /// * `statediffremoved` - Removed from base. Each vec is shortstatekey+shorteventid
+    /// * `diff_to_sibling` - Approximately how much the diff grows each time for this layer
+    /// * `parent_states` - A stack with info on shortstatehash, full state, added diff and removed diff for each parent layer
+    pub fn save_state_from_diff(
+        &self,
+        shortstatehash: u64,
+        statediffnew: HashSet<CompressedStateEvent>,
+        statediffremoved: HashSet<CompressedStateEvent>,
+        diff_to_sibling: usize,
+        mut parent_states: Vec<(
+            u64,                           // sstatehash
+            HashSet<CompressedStateEvent>, // full state
+            HashSet<CompressedStateEvent>, // added
+            HashSet<CompressedStateEvent>, // removed
+        )>,
+    ) -> Result<()> {
+        let diffsum = statediffnew.len() + statediffremoved.len();
+
+        if parent_states.len() > 3 {
+            // Number of layers
+            // To many layers, we have to go deeper
+            let parent = parent_states.pop().unwrap();
+
+            let mut parent_new = parent.2;
+            let mut parent_removed = parent.3;
+
+            for removed in statediffremoved {
+                if !parent_new.remove(&removed) {
+                    parent_removed.insert(removed);
+                }
+            }
+            parent_new.extend(statediffnew);
+
+            self.save_state_from_diff(
+                shortstatehash,
+                parent_new,
+                parent_removed,
+                diffsum,
+                parent_states,
+            )?;
+
+            return Ok(());
+        }
+
+        if parent_states.len() == 0 {
+            // There is no parent layer, create a new state
+            let mut value = 0_u64.to_be_bytes().to_vec(); // 0 means no parent
+            for new in &statediffnew {
+                value.extend_from_slice(&new[..]);
+            }
+
+            if !statediffremoved.is_empty() {
+                warn!("Tried to create new state with removals");
+            }
+
+            self.shortstatehash_statediff
+                .insert(&shortstatehash.to_be_bytes(), &value)?;
+
+            return Ok(());
+        };
+
+        // Else we have two options.
+        // 1. We add the current diff on top of the parent layer.
+        // 2. We replace a layer above
+
+        let parent = parent_states.pop().unwrap();
+        let parent_diff = parent.2.len() + parent.3.len();
+
+        if diffsum * diffsum >= 2 * diff_to_sibling * parent_diff {
+            // Diff too big, we replace above layer(s)
+            let mut parent_new = parent.2;
+            let mut parent_removed = parent.3;
+
+            for removed in statediffremoved {
+                if !parent_new.remove(&removed) {
+                    parent_removed.insert(removed);
+                }
+            }
+
+            parent_new.extend(statediffnew);
+            self.save_state_from_diff(
+                shortstatehash,
+                parent_new,
+                parent_removed,
+                diffsum,
+                parent_states,
+            )?;
+        } else {
+            // Diff small enough, we add diff as layer on top of parent
+            let mut value = parent.0.to_be_bytes().to_vec();
+            for new in &statediffnew {
+                value.extend_from_slice(&new[..]);
+            }
+
+            if !statediffremoved.is_empty() {
+                value.extend_from_slice(&0_u64.to_be_bytes());
+                for removed in &statediffremoved {
+                    value.extend_from_slice(&removed[..]);
+                }
+            }
+
+            self.shortstatehash_statediff
+                .insert(&shortstatehash.to_be_bytes(), &value)?;
+        }
 
         Ok(())
     }
@@ -418,7 +608,6 @@ impl Rooms {
         })
     }
 
-    /// Returns (shortstatehash, already_existed)
     pub fn get_or_create_shorteventid(
         &self,
         event_id: &EventId,
@@ -438,6 +627,71 @@ impl Rooms {
         })
     }
 
+    pub fn get_shortroomid(&self, room_id: &RoomId) -> Result<u64> {
+        let bytes = self
+            .roomid_shortroomid
+            .get(&room_id.as_bytes())?
+            .expect("every room has a shortroomid");
+        utils::u64_from_bytes(&bytes).map_err(|_| Error::bad_database("Invalid shortroomid in db."))
+    }
+
+    pub fn get_shortstatekey(
+        &self,
+        event_type: &EventType,
+        state_key: &str,
+    ) -> Result<Option<u64>> {
+        let mut statekey = event_type.as_ref().as_bytes().to_vec();
+        statekey.push(0xff);
+        statekey.extend_from_slice(&state_key.as_bytes());
+
+        self.statekey_shortstatekey
+            .get(&statekey)?
+            .map(|shortstatekey| {
+                utils::u64_from_bytes(&shortstatekey)
+                    .map_err(|_| Error::bad_database("Invalid shortstatekey in db."))
+            })
+            .transpose()
+    }
+
+    pub fn get_or_create_shortroomid(
+        &self,
+        room_id: &RoomId,
+        globals: &super::globals::Globals,
+    ) -> Result<u64> {
+        Ok(match self.roomid_shortroomid.get(&room_id.as_bytes())? {
+            Some(short) => utils::u64_from_bytes(&short)
+                .map_err(|_| Error::bad_database("Invalid shortroomid in db."))?,
+            None => {
+                let short = globals.next_count()?;
+                self.roomid_shortroomid
+                    .insert(&room_id.as_bytes(), &short.to_be_bytes())?;
+                short
+            }
+        })
+    }
+
+    pub fn get_or_create_shortstatekey(
+        &self,
+        event_type: &EventType,
+        state_key: &str,
+        globals: &super::globals::Globals,
+    ) -> Result<u64> {
+        let mut statekey = event_type.as_ref().as_bytes().to_vec();
+        statekey.push(0xff);
+        statekey.extend_from_slice(&state_key.as_bytes());
+
+        Ok(match self.statekey_shortstatekey.get(&statekey)? {
+            Some(shortstatekey) => utils::u64_from_bytes(&shortstatekey)
+                .map_err(|_| Error::bad_database("Invalid shortstatekey in db."))?,
+            None => {
+                let shortstatekey = globals.next_count()?;
+                self.statekey_shortstatekey
+                    .insert(&statekey, &shortstatekey.to_be_bytes())?;
+                shortstatekey
+            }
+        })
+    }
+
     pub fn get_eventid_from_short(&self, shorteventid: u64) -> Result<EventId> {
         if let Some(id) = self
             .shorteventid_cache
@@ -514,7 +768,7 @@ impl Rooms {
     #[tracing::instrument(skip(self))]
     pub fn pdu_count(&self, pdu_id: &[u8]) -> Result<u64> {
         Ok(
-            utils::u64_from_bytes(&pdu_id[pdu_id.len() - mem::size_of::<u64>()..pdu_id.len()])
+            utils::u64_from_bytes(&pdu_id[pdu_id.len() - size_of::<u64>()..])
                 .map_err(|_| Error::bad_database("PDU has invalid count bytes."))?,
         )
     }
@@ -527,8 +781,7 @@ impl Rooms {
     }
 
     pub fn latest_pdu_count(&self, room_id: &RoomId) -> Result<u64> {
-        let mut prefix = room_id.as_bytes().to_vec();
+        let prefix = self.get_shortroomid(room_id)?.to_be_bytes().to_vec();
-        prefix.push(0xff);
 
         let mut last_possible_key = prefix.clone();
         last_possible_key.extend_from_slice(&u64::MAX.to_be_bytes());
@@ -758,6 +1011,8 @@ impl Rooms {
     ///
     /// By this point the incoming event should be fully authenticated, no auth happens
     /// in `append_pdu`.
+    ///
+    /// Returns pdu id
     #[tracing::instrument(skip(self, pdu, pdu_json, leaves, db))]
     pub fn append_pdu(
         &self,
@@ -766,7 +1021,8 @@ impl Rooms {
         leaves: &[EventId],
         db: &Database,
     ) -> Result<Vec<u8>> {
-        // returns pdu id
+        let shortroomid = self.get_shortroomid(&pdu.room_id)?;
+
         // Make unsigned fields correct. This is not properly documented in the spec, but state
         // events need to have previous content in the unsigned field, so clients can easily
         // interpret things like membership changes
@@ -821,8 +1077,7 @@ impl Rooms {
         self.reset_notification_counts(&pdu.sender, &pdu.room_id)?;
 
         let count2 = db.globals.next_count()?;
-        let mut pdu_id = pdu.room_id.as_bytes().to_vec();
+        let mut pdu_id = shortroomid.to_be_bytes().to_vec();
-        pdu_id.push(0xff);
         pdu_id.extend_from_slice(&count2.to_be_bytes());
 
         // There's a brief moment of time here where the count is updated but the pdu does not
@@ -968,8 +1223,7 @@ impl Rooms {
                         .filter(|word| word.len() <= 50)
                         .map(str::to_lowercase)
                         .map(|word| {
-                            let mut key = pdu.room_id.as_bytes().to_vec();
+                            let mut key = shortroomid.to_be_bytes().to_vec();
-                            key.push(0xff);
                             key.extend_from_slice(word.as_bytes());
                             key.push(0xff);
                             key.extend_from_slice(&pdu_id);
@@ -1152,11 +1406,27 @@ impl Rooms {
     pub fn set_event_state(
         &self,
         event_id: &EventId,
+        room_id: &RoomId,
         state: &StateMap<Arc<PduEvent>>,
         globals: &super::globals::Globals,
     ) -> Result<()> {
         let shorteventid = self.get_or_create_shorteventid(&event_id, globals)?;
 
+        let previous_shortstatehash = self.current_shortstatehash(&room_id)?;
+
+        let state_ids_compressed = state
+            .iter()
+            .filter_map(|((event_type, state_key), pdu)| {
+                let shortstatekey = self
+                    .get_or_create_shortstatekey(event_type, state_key, globals)
+                    .ok()?;
+                Some(
+                    self.compress_state_event(shortstatekey, &pdu.event_id, globals)
+                        .ok()?,
+                )
+            })
+            .collect::<HashSet<_>>();
+
         let state_hash = self.calculate_hash(
             &state
                 .values()
@@ -1168,37 +1438,33 @@ impl Rooms {
             self.get_or_create_shortstatehash(&state_hash, globals)?;
 
         if !already_existed {
-            let batch = state
+            let states_parents = previous_shortstatehash
-                .iter()
+                .map_or_else(|| Ok(Vec::new()), |p| self.load_shortstatehash_info(p))?;
-                .filter_map(|((event_type, state_key), pdu)| {
-                    let mut statekey = event_type.as_ref().as_bytes().to_vec();
-                    statekey.push(0xff);
-                    statekey.extend_from_slice(&state_key.as_bytes());
 
-                    let shortstatekey = match self.statekey_shortstatekey.get(&statekey).ok()? {
+            let (statediffnew, statediffremoved) =
-                        Some(shortstatekey) => shortstatekey.to_vec(),
+                if let Some(parent_stateinfo) = states_parents.last() {
-                        None => {
+                    let statediffnew = state_ids_compressed
-                            let shortstatekey = globals.next_count().ok()?;
+                        .difference(&parent_stateinfo.1)
-                            self.statekey_shortstatekey
+                        .cloned()
-                                .insert(&statekey, &shortstatekey.to_be_bytes())
+                        .collect::<HashSet<_>>();
-                                .ok()?;
+
-                            shortstatekey.to_be_bytes().to_vec()
+                    let statediffremoved = parent_stateinfo
-                        }
+                        .1
+                        .difference(&state_ids_compressed)
+                        .cloned()
+                        .collect::<HashSet<_>>();
+
+                    (statediffnew, statediffremoved)
+                } else {
+                    (state_ids_compressed, HashSet::new())
                 };
-
+            self.save_state_from_diff(
-                    let shorteventid = self
+                shortstatehash,
-                        .get_or_create_shorteventid(&pdu.event_id, globals)
+                statediffnew.clone(),
-                        .ok()?;
+                statediffremoved.clone(),
-
+                1_000_000, // high number because no state will be based on this one
-                    let mut state_id = shortstatehash.to_be_bytes().to_vec();
+                states_parents,
-                    state_id.extend_from_slice(&shortstatekey);
+            )?;
-
-                    Some((state_id, shorteventid.to_be_bytes().to_vec()))
-                })
-                .collect::<Vec<_>>();
-
-            self.stateid_shorteventid
-                .insert_batch(&mut batch.into_iter())?;
         }
 
         self.shorteventid_shortstatehash
@@ -1219,82 +1485,52 @@ impl Rooms {
     ) -> Result<u64> {
         let shorteventid = self.get_or_create_shorteventid(&new_pdu.event_id, globals)?;
 
-        let old_state = if let Some(old_shortstatehash) =
+        let previous_shortstatehash = self.current_shortstatehash(&new_pdu.room_id)?;
-            self.roomid_shortstatehash.get(new_pdu.room_id.as_bytes())?
+
-        {
+        if let Some(p) = previous_shortstatehash {
-            // Store state for event. The state does not include the event itself.
-            // Instead it's the state before the pdu, so the room's old state.
             self.shorteventid_shortstatehash
-                .insert(&shorteventid.to_be_bytes(), &old_shortstatehash)?;
+                .insert(&shorteventid.to_be_bytes(), &p.to_be_bytes())?;
-
-            if new_pdu.state_key.is_none() {
-                return utils::u64_from_bytes(&old_shortstatehash).map_err(|_| {
-                    Error::bad_database("Invalid shortstatehash in roomid_shortstatehash.")
-                });
         }
 
-            self.stateid_shorteventid
-                .scan_prefix(old_shortstatehash.clone())
-                // Chop the old_shortstatehash out leaving behind the short state key
-                .map(|(k, v)| (k[old_shortstatehash.len()..].to_vec(), v))
-                .collect::<HashMap<Vec<u8>, Vec<u8>>>()
-        } else {
-            HashMap::new()
-        };
-
         if let Some(state_key) = &new_pdu.state_key {
-            let mut new_state: HashMap<Vec<u8>, Vec<u8>> = old_state;
+            let states_parents = previous_shortstatehash
+                .map_or_else(|| Ok(Vec::new()), |p| self.load_shortstatehash_info(p))?;
 
-            let mut new_state_key = new_pdu.kind.as_ref().as_bytes().to_vec();
+            let shortstatekey =
-            new_state_key.push(0xff);
+                self.get_or_create_shortstatekey(&new_pdu.kind, &state_key, globals)?;
-            new_state_key.extend_from_slice(state_key.as_bytes());
 
-            let shortstatekey = match self.statekey_shortstatekey.get(&new_state_key)? {
+            let replaces = states_parents
-                Some(shortstatekey) => shortstatekey.to_vec(),
+                .last()
-                None => {
+                .map(|info| {
-                    let shortstatekey = globals.next_count()?;
+                    info.1
-                    self.statekey_shortstatekey
+                        .iter()
-                        .insert(&new_state_key, &shortstatekey.to_be_bytes())?;
+                        .find(|bytes| bytes.starts_with(&shortstatekey.to_be_bytes()))
-                    shortstatekey.to_be_bytes().to_vec()
+                })
-                }
+                .unwrap_or_default();
-            };
 
-            new_state.insert(shortstatekey, shorteventid.to_be_bytes().to_vec());
+            // TODO: statehash with deterministic inputs
-
-            let new_state_hash = self.calculate_hash(
-                &new_state
-                    .values()
-                    .map(|event_id| &**event_id)
-                    .collect::<Vec<_>>(),
-            );
-
-            let shortstatehash = match self.statehash_shortstatehash.get(&new_state_hash)? {
-                Some(shortstatehash) => {
-                    warn!("state hash already existed?!");
-                    utils::u64_from_bytes(&shortstatehash)
-                        .map_err(|_| Error::bad_database("PDU has invalid count bytes."))?
-                }
-                None => {
             let shortstatehash = globals.next_count()?;
-                    self.statehash_shortstatehash
+
-                        .insert(&new_state_hash, &shortstatehash.to_be_bytes())?;
+            let mut statediffnew = HashSet::new();
-                    shortstatehash
+            let new = self.compress_state_event(shortstatekey, &new_pdu.event_id, globals)?;
+            statediffnew.insert(new);
+
+            let mut statediffremoved = HashSet::new();
+            if let Some(replaces) = replaces {
+                statediffremoved.insert(replaces.clone());
             }
-            };
 
-            let mut batch = new_state.into_iter().map(|(shortstatekey, shorteventid)| {
+            self.save_state_from_diff(
-                let mut state_id = shortstatehash.to_be_bytes().to_vec();
+                shortstatehash,
-                state_id.extend_from_slice(&shortstatekey);
+                statediffnew,
-                (state_id, shorteventid)
+                statediffremoved,
-            });
+                2,
-
+                states_parents,
-            self.stateid_shorteventid.insert_batch(&mut batch)?;
+            )?;
 
             Ok(shortstatehash)
         } else {
-            Err(Error::bad_database(
+            Ok(previous_shortstatehash.expect("first event in room must be a state event"))
-                "Tried to insert non-state event into room without a state.",
-            ))
         }
     }
 
@@ -1597,7 +1833,7 @@ impl Rooms {
         &'a self,
         user_id: &UserId,
         room_id: &RoomId,
-    ) -> impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a {
+    ) -> Result<impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a> {
         self.pdus_since(user_id, room_id, 0)
     }
 
@@ -1609,16 +1845,17 @@ impl Rooms {
         user_id: &UserId,
         room_id: &RoomId,
         since: u64,
-    ) -> impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a {
+    ) -> Result<impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a> {
-        let mut prefix = room_id.as_bytes().to_vec();
+        let prefix = self.get_shortroomid(room_id)?.to_be_bytes().to_vec();
-        prefix.push(0xff);
 
         // Skip the first pdu if it's exactly at since, because we sent that last time
         let mut first_pdu_id = prefix.clone();
         first_pdu_id.extend_from_slice(&(since + 1).to_be_bytes());
 
         let user_id = user_id.clone();
-        self.pduid_pdu
+
+        Ok(self
+            .pduid_pdu
             .iter_from(&first_pdu_id, false)
             .take_while(move |(k, _)| k.starts_with(&prefix))
             .map(move |(pdu_id, v)| {
@@ -1628,7 +1865,7 @@ impl Rooms {
                     pdu.unsigned.remove("transaction_id");
                 }
                 Ok((pdu_id, pdu))
-            })
+            }))
     }
 
     /// Returns an iterator over all events and their tokens in a room that happened before the
@@ -1639,10 +1876,9 @@ impl Rooms {
         user_id: &UserId,
         room_id: &RoomId,
         until: u64,
-    ) -> impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a {
+    ) -> Result<impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a> {
         // Create the first part of the full pdu id
-        let mut prefix = room_id.as_bytes().to_vec();
+        let prefix = self.get_shortroomid(room_id)?.to_be_bytes().to_vec();
-        prefix.push(0xff);
 
         let mut current = prefix.clone();
         current.extend_from_slice(&(until.saturating_sub(1)).to_be_bytes()); // -1 because we don't want event at `until`
@@ -1650,7 +1886,9 @@ impl Rooms {
         let current: &[u8] = &current;
 
         let user_id = user_id.clone();
-        self.pduid_pdu
+
+        Ok(self
+            .pduid_pdu
             .iter_from(current, true)
             .take_while(move |(k, _)| k.starts_with(&prefix))
             .map(move |(pdu_id, v)| {
@@ -1660,7 +1898,7 @@ impl Rooms {
                     pdu.unsigned.remove("transaction_id");
                 }
                 Ok((pdu_id, pdu))
-            })
+            }))
     }
 
     /// Returns an iterator over all events and their token in a room that happened after the event
@@ -1671,10 +1909,9 @@ impl Rooms {
         user_id: &UserId,
         room_id: &RoomId,
         from: u64,
-    ) -> impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a {
+    ) -> Result<impl Iterator<Item = Result<(Vec<u8>, PduEvent)>> + 'a> {
         // Create the first part of the full pdu id
-        let mut prefix = room_id.as_bytes().to_vec();
+        let prefix = self.get_shortroomid(room_id)?.to_be_bytes().to_vec();
-        prefix.push(0xff);
 
         let mut current = prefix.clone();
         current.extend_from_slice(&(from + 1).to_be_bytes()); // +1 so we don't send the base event
@@ -1682,7 +1919,9 @@ impl Rooms {
         let current: &[u8] = &current;
 
         let user_id = user_id.clone();
-        self.pduid_pdu
+
+        Ok(self
+            .pduid_pdu
             .iter_from(current, false)
             .take_while(move |(k, _)| k.starts_with(&prefix))
             .map(move |(pdu_id, v)| {
@@ -1692,7 +1931,7 @@ impl Rooms {
                     pdu.unsigned.remove("transaction_id");
                 }
                 Ok((pdu_id, pdu))
-            })
+            }))
     }
 
     /// Replace a PDU with the redacted form.
@@ -2223,8 +2462,8 @@ impl Rooms {
         room_id: &RoomId,
         search_string: &str,
     ) -> Result<(impl Iterator<Item = Vec<u8>> + 'a, Vec<String>)> {
-        let mut prefix = room_id.as_bytes().to_vec();
+        let prefix = self.get_shortroomid(room_id)?.to_be_bytes().to_vec();
-        prefix.push(0xff);
+        let prefix_clone = prefix.clone();
 
         let words = search_string
             .split_terminator(|c: char| !c.is_alphanumeric())
@@ -2243,16 +2482,7 @@ impl Rooms {
                 .iter_from(&last_possible_id, true) // Newest pdus first
                 .take_while(move |(k, _)| k.starts_with(&prefix2))
                 .map(|(key, _)| {
-                    let pduid_index = key
+                    let pdu_id = key[key.len() - size_of::<u64>()..].to_vec();
-                        .iter()
-                        .enumerate()
-                        .filter(|(_, &b)| b == 0xff)
-                        .nth(1)
-                        .ok_or_else(|| Error::bad_database("Invalid tokenid in db."))?
-                        .0
-                        + 1; // +1 because the pdu id starts AFTER the separator
-
-                    let pdu_id = key[pduid_index..].to_vec();
 
                     Ok::<_, Error>(pdu_id)
                 })
@@ -2264,7 +2494,12 @@ impl Rooms {
                 // We compare b with a because we reversed the iterator earlier
                 b.cmp(a)
             })
-            .unwrap(),
+            .unwrap()
+            .map(move |id| {
+                let mut pduid = prefix_clone.clone();
+                pduid.extend_from_slice(&id);
+                pduid
+            }),
             words,
         ))
     }

src/server_server.rs

@@ -1704,7 +1704,7 @@ fn append_incoming_pdu(
     // We append to state before appending the pdu, so we don't have a moment in time with the
     // pdu without it's state. This is okay because append_pdu can't fail.
     db.rooms
-        .set_event_state(&pdu.event_id, state, &db.globals)?;
+        .set_event_state(&pdu.event_id, &pdu.room_id, state, &db.globals)?;
 
     let pdu_id = db.rooms.append_pdu(
         pdu,