29 changed files with 1928 additions and 105 deletions
--- a/Cargo.lock
+++ b/Cargo.lock
@ -180,6 +180,15 @@ version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "904dfeac50f3cdaba28fc6f57fdcddb75f49ed61346676a78c4ffe55877802fd"

+[[package]]
+name = "bincode"
+version = "1.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b1f45e9417d87227c7a56d22e471c6206462cba514c7590c09aff4cf6d1ddcad"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "bitflags"
 version = "1.2.1"
@ -1194,6 +1203,12 @@ version = "2.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b16bd47d9e329435e309c58469fe0791c2d0d1ba96ec0954152a5ae2b04387dc"

+[[package]]
+name = "memmem"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a64a92489e2744ce060c349162be1c5f33c6969234104dbd99ddb5feb08b8c15"
+
 [[package]]
 name = "memoffset"
 version = "0.6.3"
@ -2498,6 +2513,8 @@ version = "0.10.0"
 dependencies = [
 "async-trait",
 "barrel",
+ "bincode",
+ "byteorder",
 "combine",
 "dirs",
 "futures",
@ -2506,11 +2523,13 @@ dependencies = [
 "itertools",
 "log",
 "matrix-sdk",
+ "memmem",
 "nom 5.1.2",
 "phf",
 "rand 0.8.3",
 "refinery",
 "serde",
+ "sled",
 "sqlx",
 "tempfile",
 "thiserror",
@ -2518,6 +2537,7 @@ dependencies = [
 "toml",
 "tracing-subscriber",
 "url",
+ "zerocopy",
 ]

 [[package]]
@ -3073,6 +3093,27 @@ dependencies = [
 "time 0.1.43",
 ]

+[[package]]
+name = "zerocopy"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5e59ec1d2457bd6c0dd89b50e7d9d6b0b647809bf3f0a59ac85557046950b7b2"
+dependencies = [
+ "byteorder",
+ "zerocopy-derive",
+]
+
+[[package]]
+name = "zerocopy-derive"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0af017aca1fa6181f5dd7a802456fe6f7666ecdcc18d0910431f0fc89d474e51"
+dependencies = [
+ "proc-macro2",
+ "syn",
+ "synstructure",
+]
+
 [[package]]
 name = "zeroize"
 version = "1.3.0"
--- a/Cargo.toml
+++ b/Cargo.toml
@ -27,7 +27,12 @@ url = "2.1"
 dirs = "3.0"
 indoc = "1.0"
 combine = "4.5"
+sled = "0.34"
+zerocopy = "0.5"
+byteorder = "1.3"
 futures = "0.3"
+memmem = "0.1"
+bincode = "1.3"
 html2text = "0.2"
 phf = { version = "0.8", features = ["macros"] }
 matrix-sdk = { git = "https://github.com/matrix-org/matrix-rust-sdk", branch = "master" }
--- a/src/bin/migrate_sled.rs
+++ b/src/bin/migrate_sled.rs
@ -0,0 +1,37 @@
+use tenebrous_dicebot::db::sqlite::{Database as SqliteDatabase, Variables};
+use tenebrous_dicebot::db::Database;
+use tenebrous_dicebot::error::BotError;
+
+#[tokio::main]
+async fn main() -> Result<(), BotError> {
+    let sled_path = std::env::args()
+        .skip(1)
+        .next()
+        .expect("Need a path to a Sled database as an arument.");
+
+    let sqlite_path = std::env::args()
+        .skip(2)
+        .next()
+        .expect("Need a path to an sqlite database as an arument.");
+
+    let db = Database::new(&sled_path)?;
+
+    let all_variables = db.variables.get_all_variables()?;
+
+    let sql_db = SqliteDatabase::new(&sqlite_path).await?;
+
+    for var in all_variables {
+        if let ((username, room_id, variable_name), value) = var {
+            println!(
+                "Migrating {}::{}::{} = {} to sql",
+                username, room_id, variable_name, value
+            );
+
+            sql_db
+                .set_user_variable(&username, &room_id, &variable_name, value)
+                .await;
+        }
+    }
+
+    Ok(())
+}
--- a/src/bot.rs
+++ b/src/bot.rs
@ -2,7 +2,7 @@ use crate::commands::{execute_command, ExecutionError, ExecutionResult, Response
 use crate::config::*;
 use crate::context::{Context, RoomContext};
 use crate::db::sqlite::Database;
-use crate::db::DbState;
+use crate::db::sqlite::DbState;
 use crate::error::BotError;
 use crate::matrix;
 use crate::state::DiceBotState;
--- a/src/bot/event_handlers.rs
+++ b/src/bot/event_handlers.rs
@ -5,7 +5,7 @@
 */
 use super::DiceBot;
 use crate::db::sqlite::Database;
-use crate::db::Rooms;
+use crate::db::sqlite::Rooms;
 use crate::error::BotError;
 use crate::logic::record_room_information;
 use async_trait::async_trait;
--- a/src/cofd/dice.rs
+++ b/src/cofd/dice.rs
@ -326,7 +326,7 @@ pub async fn roll_pool(pool: &DicePoolWithContext<'_>) -> Result<RolledDicePool,
 mod tests {
    use super::*;
    use crate::db::sqlite::Database;
-    use crate::db::Variables;
+    use crate::db::sqlite::Variables;
    use url::Url;

    macro_rules! dummy_room {
--- a/src/commands.rs
+++ b/src/commands.rs
@ -2,7 +2,7 @@ use crate::context::Context;
 use crate::error::BotError;
 use async_trait::async_trait;
 use thiserror::Error;
-use BotError::DataError;
+use BotError::{DataError, SqliteDataError};

 pub mod basic_rolling;
 pub mod cofd;
@ -55,6 +55,12 @@ impl From<crate::db::errors::DataError> for ExecutionError {
    }
 }

+impl From<crate::db::sqlite::errors::DataError> for ExecutionError {
+    fn from(error: crate::db::sqlite::errors::DataError) -> Self {
+        Self(SqliteDataError(error))
+    }
+}
+
 impl ExecutionError {
    /// Error message in bolded HTML.
    pub fn html(&self) -> String {
--- a/src/commands/variables.rs
+++ b/src/commands/variables.rs
@ -1,7 +1,8 @@
 use super::{Command, Execution, ExecutionResult};
 use crate::context::Context;
-use crate::db::errors::DataError;
-use crate::db::Variables;
+use crate::db::sqlite::errors::DataError;
+use crate::db::sqlite::Variables;
+use crate::db::variables::UserAndRoom;
 use async_trait::async_trait;

 pub struct GetAllVariablesCommand;
--- a/src/cthulhu/dice.rs
+++ b/src/cthulhu/dice.rs
@ -1,7 +1,7 @@
-use crate::context::Context;
-use crate::db::Variables;
+use crate::db::sqlite::Variables;
 use crate::error::{BotError, DiceRollingError};
 use crate::parser::{Amount, Element};
+use crate::{context::Context, db::variables::UserAndRoom};
 use crate::{dice::calculate_single_die_amount, parser::DiceParsingError};
 use rand::rngs::StdRng;
 use rand::Rng;
--- a/src/db.rs
+++ b/src/db.rs
@ -0,0 +1,98 @@
+use crate::db::errors::{DataError, MigrationError};
+use crate::db::migrations::{get_migration_version, Migrations};
+use crate::db::rooms::Rooms;
+use crate::db::state::DbState;
+use crate::db::variables::Variables;
+use log::info;
+use sled::{Config, Db};
+use std::path::Path;
+
+pub mod data_migrations;
+pub mod errors;
+pub mod migrations;
+pub mod rooms;
+pub mod schema;
+pub mod sqlite;
+pub mod state;
+pub mod variables;
+
+#[derive(Clone)]
+pub struct Database {
+    db: Db,
+    pub variables: Variables,
+    pub(crate) migrations: Migrations,
+    pub(crate) rooms: Rooms,
+    pub(crate) state: DbState,
+}
+
+impl Database {
+    fn new_db(db: sled::Db) -> Result<Database, DataError> {
+        let migrations = db.open_tree("migrations")?;
+
+        let database = Database {
+            db: db.clone(),
+            variables: Variables::new(&db)?,
+            migrations: Migrations(migrations),
+            rooms: Rooms::new(&db)?,
+            state: DbState::new(&db)?,
+        };
+
+        //Start any event handlers.
+        database.rooms.start_handler();
+
+        info!("Opened database.");
+        Ok(database)
+    }
+
+    pub fn new<P: AsRef<Path>>(path: P) -> Result<Database, DataError> {
+        let db = sled::open(path)?;
+        Self::new_db(db)
+    }
+
+    pub fn new_temp() -> Result<Database, DataError> {
+        let config = Config::new().temporary(true);
+        let db = config.open()?;
+        Self::new_db(db)
+    }
+
+    pub fn migrate(&self, to_version: u32) -> Result<(), DataError> {
+        //get version from db
+        let db_version = get_migration_version(&self)?;
+
+        if db_version < to_version {
+            info!(
+                "Migrating database from version {} to version {}",
+                db_version, to_version
+            );
+            //if db version < to_version, proceed
+            //produce range of db_version+1 .. to_version (inclusive)
+            let versions_to_run: Vec<u32> = ((db_version + 1)..=to_version).collect();
+            let migrations = data_migrations::get_migrations(&versions_to_run)?;
+
+            //execute each closure.
+            for (version, migration) in versions_to_run.iter().zip(migrations) {
+                let (migration_func, name) = migration;
+                //This needs to be transactional on migrations
+                //keyspace. abort on migration func error.
+
+                info!("Applying migration {} :: {}", version, name);
+                match migration_func(&self) {
+                    Ok(_) => Ok(()),
+                    Err(e) => Err(e),
+                }?;
+
+                self.migrations.set_migration_version(*version)?;
+            }
+
+            info!("Done applying migrations.");
+            Ok(())
+        } else if db_version > to_version {
+            //if db version > to_version, cannot downgrade error
+            Err(MigrationError::CannotDowngrade.into())
+        } else {
+            //if db version == to_version, do nothing
+            info!("No database migrations needed.");
+            Ok(())
+        }
+    }
+}
--- a/src/db/data_migrations.rs
+++ b/src/db/data_migrations.rs
@ -0,0 +1,28 @@
+use crate::db::errors::{DataError, MigrationError};
+use crate::db::variables::migrations::*;
+use crate::db::Database;
+use phf::phf_map;
+
+pub(super) type DataMigration = (fn(&Database) -> Result<(), DataError>, &'static str);
+
+static MIGRATIONS: phf::Map<u32, DataMigration> = phf_map! {
+    1u32 => (add_room_user_variable_count::migrate, "add_room_user_variable_count"),
+    2u32 => (delete_v0_schema, "delete_v0_schema"),
+    3u32 => (delete_variable_count, "delete_variable_count"),
+    4u32 => (change_delineator_delimiter::migrate, "change_delineator_delimiter"),
+    5u32 => (change_tree_structure::migrate, "change_tree_structure"),
+
+};
+
+pub fn get_migrations(versions: &[u32]) -> Result<Vec<DataMigration>, MigrationError> {
+    let mut migrations: Vec<DataMigration> = vec![];
+
+    for version in versions {
+        match MIGRATIONS.get(version) {
+            Some(func) => migrations.push(*func),
+            None => return Err(MigrationError::MigrationNotFound(*version)),
+        }
+    }
+
+    Ok(migrations)
+}
--- a/src/db/errors.rs
+++ b/src/db/errors.rs
@ -1,6 +1,20 @@
-use std::num::TryFromIntError;
+use sled::transaction::{TransactionError, UnabortableTransactionError};
 use thiserror::Error;

+#[derive(Error, Debug)]
+pub enum MigrationError {
+    #[error("cannot downgrade to an older database version")]
+    CannotDowngrade,
+
+    #[error("migration for version {0} not defined")]
+    MigrationNotFound(u32),
+
+    #[error("migration failed: {0}")]
+    MigrationFailed(String),
+}
+
+//TODO better combining of key and value in certain errors (namely
+//I32SchemaViolation).
 #[derive(Error, Debug)]
 pub enum DataError {
    #[error("value does not exist for key: {0}")]
@ -12,6 +26,9 @@ pub enum DataError {
    #[error("expected i32, but i32 schema was violated")]
    I32SchemaViolation,

+    #[error("parse error")]
+    ParseError(#[from] std::num::ParseIntError),
+
    #[error("unexpected or corruptd data bytes")]
    InvalidValue,

@ -21,12 +38,44 @@ pub enum DataError {
    #[error("expected string, but utf8 schema was violated: {0}")]
    Utf8SchemaViolation(#[from] std::string::FromUtf8Error),

-    #[error("data migration error: {0}")]
-    MigrationError(#[from] crate::db::sqlite::migrator::MigrationError),
-
    #[error("internal database error: {0}")]
-    SqlxError(#[from] sqlx::Error),
+    InternalError(#[from] sled::Error),

-    #[error("numeric conversion error")]
-    NumericConversionError(#[from] TryFromIntError),
+    #[error("transaction error: {0}")]
+    TransactionError(#[from] sled::transaction::TransactionError),
+
+    #[error("unabortable transaction error: {0}")]
+    UnabortableTransactionError(#[from] UnabortableTransactionError),
+
+    #[error("data migration error: {0}")]
+    MigrationError(#[from] MigrationError),
+
+    #[error("deserialization error: {0}")]
+    DeserializationError(#[from] bincode::Error),
+}
+
+/// This From implementation is necessary to deal with the recursive
+/// error type in the error enum. We defined a transaction error, but
+/// the only place we use it is when converting from
+/// sled::transaction::TransactionError<DataError>. This converter
+/// extracts the inner data error from transaction aborted errors, and
+/// forwards anything else onward as-is, but wrapped in DataError.
+impl From<TransactionError<DataError>> for DataError {
+    fn from(error: TransactionError<DataError>) -> Self {
+        match error {
+            TransactionError::Abort(data_err) => data_err,
+            TransactionError::Storage(storage_err) => {
+                DataError::TransactionError(TransactionError::Storage(storage_err))
+            }
+        }
+    }
+}
+
+/// Automatically aborts transactions that hit a DataError by using
+/// the try (question mark) operator when this trait implementation is
+/// in scope.
+impl From<DataError> for sled::transaction::ConflictableTransactionError<DataError> {
+    fn from(error: DataError) -> Self {
+        sled::transaction::ConflictableTransactionError::Abort(error)
+    }
 }
--- a/src/db/migrations.rs
+++ b/src/db/migrations.rs
@ -0,0 +1,54 @@
+use crate::db::errors::DataError;
+use crate::db::schema::convert_u32;
+use crate::db::Database;
+use byteorder::LittleEndian;
+use sled::Tree;
+use zerocopy::byteorder::U32;
+use zerocopy::AsBytes;
+
+//This file is for controlling the migration info stored in the
+//database, not actually running migrations.
+
+#[derive(Clone)]
+pub struct Migrations(pub(super) Tree);
+
+const COLON: &'static [u8] = b":";
+const METADATA_SPACE: &'static str = "metadata";
+const MIGRATION_KEY: &'static str = "migration_version";
+
+fn to_key(keyspace: &str, key_name: &str) -> Vec<u8> {
+    let mut key = vec![];
+    key.extend_from_slice(keyspace.as_bytes());
+    key.extend_from_slice(COLON);
+    key.extend_from_slice(key_name.as_bytes());
+    key
+}
+
+fn metadata_key(key_name: &str) -> Vec<u8> {
+    to_key(METADATA_SPACE, key_name)
+}
+
+impl Migrations {
+    pub(super) fn set_migration_version(&self, version: u32) -> Result<(), DataError> {
+        //Rust cannot type infer this transaction
+        let result: Result<_, sled::transaction::TransactionError<DataError>> =
+            self.0.transaction(|tx| {
+                let key = metadata_key(MIGRATION_KEY);
+                let db_value: U32<LittleEndian> = U32::new(version);
+                tx.insert(key, db_value.as_bytes())?;
+                Ok(())
+            });
+
+        result?;
+
+        Ok(())
+    }
+}
+
+pub(super) fn get_migration_version(db: &Database) -> Result<u32, DataError> {
+    let key = metadata_key(MIGRATION_KEY);
+    match db.migrations.0.get(key)? {
+        Some(bytes) => convert_u32(&bytes),
+        None => Ok(0),
+    }
+}
--- a/src/db/mod.rs
+++ b/src/db/mod.rs
@ -1,69 +0,0 @@
-use async_trait::async_trait;
-use errors::DataError;
-use std::collections::{HashMap, HashSet};
-
-use crate::models::RoomInfo;
-
-pub mod errors;
-pub mod sqlite;
-
-#[async_trait]
-pub(crate) trait DbState {
-    async fn get_device_id(&self) -> Result<Option<String>, DataError>;
-
-    async fn set_device_id(&self, device_id: &str) -> Result<(), DataError>;
-}
-
-#[async_trait]
-pub(crate) trait Rooms {
-    async fn should_process(&self, room_id: &str, event_id: &str) -> Result<bool, DataError>;
-
-    async fn insert_room_info(&self, info: &RoomInfo) -> Result<(), DataError>;
-
-    async fn get_room_info(&self, room_id: &str) -> Result<Option<RoomInfo>, DataError>;
-
-    async fn get_rooms_for_user(&self, user_id: &str) -> Result<HashSet<String>, DataError>;
-
-    async fn get_users_in_room(&self, room_id: &str) -> Result<HashSet<String>, DataError>;
-
-    async fn add_user_to_room(&self, username: &str, room_id: &str) -> Result<(), DataError>;
-
-    async fn remove_user_from_room(&self, username: &str, room_id: &str) -> Result<(), DataError>;
-
-    async fn clear_info(&self, room_id: &str) -> Result<(), DataError>;
-}
-
-// TODO move this up to the top once we delete sled. Traits will be the
-// main API, then we can have different impls for different DBs.
-#[async_trait]
-pub trait Variables {
-    async fn get_user_variables(
-        &self,
-        user: &str,
-        room_id: &str,
-    ) -> Result<HashMap<String, i32>, DataError>;
-
-    async fn get_variable_count(&self, user: &str, room_id: &str) -> Result<i32, DataError>;
-
-    async fn get_user_variable(
-        &self,
-        user: &str,
-        room_id: &str,
-        variable_name: &str,
-    ) -> Result<i32, DataError>;
-
-    async fn set_user_variable(
-        &self,
-        user: &str,
-        room_id: &str,
-        variable_name: &str,
-        value: i32,
-    ) -> Result<(), DataError>;
-
-    async fn delete_user_variable(
-        &self,
-        user: &str,
-        room_id: &str,
-        variable_name: &str,
-    ) -> Result<(), DataError>;
-}
--- a/src/db/rooms.rs
+++ b/src/db/rooms.rs
@ -0,0 +1,515 @@
+use crate::db::errors::DataError;
+use crate::db::schema::convert_u64;
+use crate::models::RoomInfo;
+use byteorder::BigEndian;
+use log::{debug, error, log_enabled};
+use sled::transaction::TransactionalTree;
+use sled::Transactional;
+use sled::{CompareAndSwapError, Tree};
+use std::collections::HashSet;
+use std::str;
+use std::time::{SystemTime, UNIX_EPOCH};
+use tokio::task::JoinHandle;
+use zerocopy::byteorder::U64;
+use zerocopy::AsBytes;
+
+#[derive(Clone)]
+pub struct Rooms {
+    /// Room ID -> RoomInfo struct (single entries).
+    /// Key is just room ID as bytes.
+    pub(in crate::db) roomid_roominfo: Tree,
+
+    /// Room ID -> list of usernames in room.
+    pub(in crate::db) roomid_usernames: Tree,
+
+    /// Username -> list of room IDs user is in.
+    pub(in crate::db) username_roomids: Tree,
+
+    /// Room ID(str) 0xff event ID(str) -> timestamp. Records event
+    /// IDs that we have received, so we do not process twice.
+    pub(in crate::db) roomeventid_timestamp: Tree,
+
+    /// Room ID(str) 0xff timestamp(u64) -> event ID. Records event
+    /// IDs with timestamp as the primary key instead. Exists to allow
+    /// easy scanning of old roomeventid_timestamp records for
+    /// removal. Be careful with u64, it can have 0xff and 0xfe bytes.
+    /// A simple split on 0xff will not work with this key. Instead,
+    /// it is meant to be split on the first 0xff byte only, and
+    /// separated into room ID and timestamp.
+    pub(in crate::db) roomtimestamp_eventid: Tree,
+}
+
+/// An enum that can hold either a regular sled Tree, or a
+/// Transactional tree.
+#[derive(Clone, Copy)]
+enum TxableTree<'a> {
+    Tree(&'a Tree),
+    Tx(&'a TransactionalTree),
+}
+
+impl<'a> Into<TxableTree<'a>> for &'a Tree {
+    fn into(self) -> TxableTree<'a> {
+        TxableTree::Tree(self)
+    }
+}
+
+impl<'a> Into<TxableTree<'a>> for &'a TransactionalTree {
+    fn into(self) -> TxableTree<'a> {
+        TxableTree::Tx(self)
+    }
+}
+
+/// A set of functions that can be used with a sled::Tree that stores
+/// HashSets as its values. Atomicity is partially handled. If the
+/// Tree is a transactional tree, operations will be atomic.
+/// Otherwise, there is a potential non-atomic step.
+mod hashset_tree {
+    use super::*;
+
+    fn insert_set<'a, T: Into<TxableTree<'a>>>(
+        tree: T,
+        key: &[u8],
+        set: HashSet<String>,
+    ) -> Result<(), DataError> {
+        let serialized = bincode::serialize(&set)?;
+        match tree.into() {
+            TxableTree::Tree(tree) => tree.insert(key, serialized)?,
+            TxableTree::Tx(tx) => tx.insert(key, serialized)?,
+        };
+        Ok(())
+    }
+
+    pub(super) fn get_set<'a, T: Into<TxableTree<'a>>>(
+        tree: T,
+        key: &[u8],
+    ) -> Result<HashSet<String>, DataError> {
+        let set: HashSet<String> = match tree.into() {
+            TxableTree::Tree(tree) => tree.get(key)?,
+            TxableTree::Tx(tx) => tx.get(key)?,
+        }
+        .map(|bytes| bincode::deserialize::<HashSet<String>>(&bytes))
+        .unwrap_or(Ok(HashSet::new()))?;
+
+        Ok(set)
+    }
+
+    pub(super) fn remove_from_set<'a, T: Into<TxableTree<'a>> + Copy>(
+        tree: T,
+        key: &[u8],
+        value_to_remove: &str,
+    ) -> Result<(), DataError> {
+        let mut set = get_set(tree, key)?;
+        set.remove(value_to_remove);
+        insert_set(tree, key, set)?;
+        Ok(())
+    }
+
+    pub(super) fn add_to_set<'a, T: Into<TxableTree<'a>> + Copy>(
+        tree: T,
+        key: &[u8],
+        value_to_add: String,
+    ) -> Result<(), DataError> {
+        let mut set = get_set(tree, key)?;
+        set.insert(value_to_add);
+        insert_set(tree, key, set)?;
+        Ok(())
+    }
+}
+
+/// Functions that specifically relate to the "timestamp index" tree,
+/// which is stored on the Rooms instance as a tree called
+/// roomtimestamp_eventid. Tightly coupled to the event watcher in the
+/// Rooms impl, and only factored out for unit testing.
+mod timestamp_index {
+    use super::*;
+
+    /// Insert an entry from the main roomeventid_timestamp Tree into
+    /// the timestamp index. Keys in this Tree are stored as room ID
+    /// 0xff timestamp, with the value being a hashset of event IDs
+    /// received at the time. The parameters come from an insert to
+    /// that Tree, where the key is room ID 0xff event ID, and the
+    /// value is the timestamp.
+    pub(super) fn insert(
+        roomtimestamp_eventid: &Tree,
+        key: &[u8],
+        timestamp_bytes: &[u8],
+    ) -> Result<(), DataError> {
+        let parts: Vec<&[u8]> = key.split(|&b| b == 0xff).collect();
+        if let [room_id, event_id] = parts[..] {
+            let mut ts_key = room_id.to_vec();
+            ts_key.push(0xff);
+            ts_key.extend_from_slice(&timestamp_bytes);
+            log_index_record(room_id, event_id, &timestamp_bytes);
+
+            let event_id = str::from_utf8(event_id)?;
+            hashset_tree::add_to_set(roomtimestamp_eventid, &ts_key, event_id.to_owned())?;
+            Ok(())
+        } else {
+            Err(DataError::InvalidValue)
+        }
+    }
+
+    /// Log a debug message.
+    fn log_index_record(room_id: &[u8], event_id: &[u8], timestamp: &[u8]) {
+        if log_enabled!(log::Level::Debug) {
+            debug!(
+                "Recording event {} | {} received at {} in timestamp index.",
+                str::from_utf8(room_id).unwrap_or("[invalid room id]"),
+                str::from_utf8(event_id).unwrap_or("[invalid event id]"),
+                convert_u64(timestamp).unwrap_or(0)
+            );
+        }
+    }
+}
+
+impl Rooms {
+    pub(in crate::db) fn new(db: &sled::Db) -> Result<Rooms, sled::Error> {
+        Ok(Rooms {
+            roomid_roominfo: db.open_tree("roomid_roominfo")?,
+            roomid_usernames: db.open_tree("roomid_usernames")?,
+            username_roomids: db.open_tree("username_roomids")?,
+            roomeventid_timestamp: db.open_tree("roomeventid_timestamp")?,
+            roomtimestamp_eventid: db.open_tree("roomtimestamp_eventid")?,
+        })
+    }
+
+    /// Start an event subscriber that listens for inserts made by the
+    /// `should_process` function. This event handler duplicates the
+    /// entry by timestamp instead of event ID.
+    pub(in crate::db) fn start_handler(&self) -> JoinHandle<()> {
+        //Clone due to lifetime requirements.
+        let roomeventid_timestamp = self.roomeventid_timestamp.clone();
+        let roomtimestamp_eventid = self.roomtimestamp_eventid.clone();
+
+        tokio::spawn(async move {
+            let mut subscriber = roomeventid_timestamp.watch_prefix(b"");
+
+            // TODO make this handler receive kill messages somehow so
+            // we can unit test it and gracefully shut it down.
+            while let Some(event) = (&mut subscriber).await {
+                if let sled::Event::Insert { key, value } = event {
+                    match timestamp_index::insert(&roomtimestamp_eventid, &key, &value) {
+                        Err(e) => {
+                            error!("Unable to update the timestamp index: {}", e);
+                        }
+                        _ => (),
+                    }
+                }
+            }
+        })
+    }
+
+    /// Determine if an event in a room should be processed. The event
+    /// is atomically recorded and true returned if the database has
+    /// not seen tis event yet. If the event already exists in the
+    /// database, the function returns false. Events are recorded by
+    /// this function by inserting the (system-local) timestamp in
+    /// epoch seconds.
+    pub fn should_process(&self, room_id: &str, event_id: &str) -> Result<bool, DataError> {
+        let mut key = room_id.as_bytes().to_vec();
+        key.push(0xff);
+        key.extend_from_slice(event_id.as_bytes());
+
+        let timestamp: U64<BigEndian> = U64::new(
+            SystemTime::now()
+                .duration_since(UNIX_EPOCH)
+                .expect("Clock has gone backwards")
+                .as_secs(),
+        );
+
+        match self.roomeventid_timestamp.compare_and_swap(
+            key,
+            None as Option<&[u8]>,
+            Some(timestamp.as_bytes()),
+        )? {
+            Ok(()) => Ok(true),
+            Err(CompareAndSwapError { .. }) => Ok(false),
+        }
+    }
+
+    pub fn insert_room_info(&self, info: &RoomInfo) -> Result<(), DataError> {
+        let key = info.room_id.as_bytes();
+        let serialized = bincode::serialize(&info)?;
+        self.roomid_roominfo.insert(key, serialized)?;
+        Ok(())
+    }
+
+    pub fn get_room_info(&self, room_id: &str) -> Result<Option<RoomInfo>, DataError> {
+        let key = room_id.as_bytes();
+
+        let room_info: Option<RoomInfo> = self
+            .roomid_roominfo
+            .get(key)?
+            .map(|bytes| bincode::deserialize(&bytes))
+            .transpose()?;
+
+        Ok(room_info)
+    }
+
+    pub fn get_rooms_for_user(&self, username: &str) -> Result<HashSet<String>, DataError> {
+        hashset_tree::get_set(&self.username_roomids, username.as_bytes())
+    }
+
+    pub fn get_users_in_room(&self, room_id: &str) -> Result<HashSet<String>, DataError> {
+        hashset_tree::get_set(&self.roomid_usernames, room_id.as_bytes())
+    }
+
+    pub fn add_user_to_room(&self, username: &str, room_id: &str) -> Result<(), DataError> {
+        debug!("Adding user {} to room {}", username, room_id);
+        (&self.username_roomids, &self.roomid_usernames).transaction(
+            |(tx_username_rooms, tx_room_usernames)| {
+                let username_key = &username.as_bytes();
+                hashset_tree::add_to_set(tx_username_rooms, username_key, room_id.to_owned())?;
+
+                let roomid_key = &room_id.as_bytes();
+                hashset_tree::add_to_set(tx_room_usernames, roomid_key, username.to_owned())?;
+
+                Ok(())
+            },
+        )?;
+
+        Ok(())
+    }
+
+    pub fn remove_user_from_room(&self, username: &str, room_id: &str) -> Result<(), DataError> {
+        debug!("Removing user {} from room {}", username, room_id);
+        (&self.username_roomids, &self.roomid_usernames).transaction(
+            |(tx_username_rooms, tx_room_usernames)| {
+                let username_key = &username.as_bytes();
+                hashset_tree::remove_from_set(tx_username_rooms, username_key, room_id)?;
+
+                let roomid_key = &room_id.as_bytes();
+                hashset_tree::remove_from_set(tx_room_usernames, roomid_key, username)?;
+
+                Ok(())
+            },
+        )?;
+
+        Ok(())
+    }
+
+    pub fn clear_info(&self, room_id: &str) -> Result<(), DataError> {
+        debug!("Clearing all information for room {}", room_id);
+        (&self.username_roomids, &self.roomid_usernames).transaction(
+            |(tx_username_roomids, tx_roomid_usernames)| {
+                let roomid_key = room_id.as_bytes();
+                let users_in_room = hashset_tree::get_set(tx_roomid_usernames, roomid_key)?;
+
+                //Remove the room ID from every user's room ID list.
+                for username in users_in_room {
+                    hashset_tree::remove_from_set(
+                        tx_username_roomids,
+                        username.as_bytes(),
+                        room_id,
+                    )?;
+                }
+
+                //Remove this room entry for the room ID -> username tree.
+                tx_roomid_usernames.remove(roomid_key)?;
+
+                //TODO: delete roominfo struct from room info tree.
+                Ok(())
+            },
+        )?;
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use sled::Config;
+
+    fn create_test_instance() -> Rooms {
+        let config = Config::new().temporary(true);
+        let db = config.open().unwrap();
+        Rooms::new(&db).unwrap()
+    }
+
+    #[test]
+    fn add_user_to_room() {
+        let rooms = create_test_instance();
+
+        rooms
+            .add_user_to_room("testuser", "myroom")
+            .expect("Could not add user to room");
+
+        let users_in_room = rooms
+            .get_users_in_room("myroom")
+            .expect("Could not retrieve users in room");
+
+        let rooms_for_user = rooms
+            .get_rooms_for_user("testuser")
+            .expect("Could not get rooms for user");
+
+        let expected_users_in_room: HashSet<String> =
+            vec![String::from("testuser")].into_iter().collect();
+
+        let expected_rooms_for_user: HashSet<String> =
+            vec![String::from("myroom")].into_iter().collect();
+
+        assert_eq!(expected_users_in_room, users_in_room);
+        assert_eq!(expected_rooms_for_user, rooms_for_user);
+    }
+
+    #[test]
+    fn remove_user_from_room() {
+        let rooms = create_test_instance();
+
+        rooms
+            .add_user_to_room("testuser", "myroom")
+            .expect("Could not add user to room");
+
+        rooms
+            .remove_user_from_room("testuser", "myroom")
+            .expect("Could not remove user from room");
+
+        let users_in_room = rooms
+            .get_users_in_room("myroom")
+            .expect("Could not retrieve users in room");
+
+        let rooms_for_user = rooms
+            .get_rooms_for_user("testuser")
+            .expect("Could not get rooms for user");
+
+        assert_eq!(HashSet::new(), users_in_room);
+        assert_eq!(HashSet::new(), rooms_for_user);
+    }
+
+    #[test]
+    fn insert_room_info_works() {
+        let rooms = create_test_instance();
+
+        let info = RoomInfo {
+            room_id: matrix_sdk::identifiers::room_id!("!fakeroom:example.com")
+                .as_str()
+                .to_owned(),
+            room_name: "fake room name".to_owned(),
+        };
+
+        rooms
+            .insert_room_info(&info)
+            .expect("Could insert room info");
+
+        let found_info = rooms
+            .get_room_info("!fakeroom:example.com")
+            .expect("Error loading room info");
+
+        assert!(found_info.is_some());
+        assert_eq!(info, found_info.unwrap());
+    }
+
+    #[test]
+    fn insert_room_info_updates_data() {
+        let rooms = create_test_instance();
+
+        let mut info = RoomInfo {
+            room_id: matrix_sdk::identifiers::room_id!("!fakeroom:example.com")
+                .as_str()
+                .to_owned(),
+            room_name: "fake room name".to_owned(),
+        };
+
+        rooms
+            .insert_room_info(&info)
+            .expect("Could insert room info");
+
+        //Update info to have a new room name before inserting again.
+        info.room_name = "new fake room name".to_owned();
+
+        rooms
+            .insert_room_info(&info)
+            .expect("Could insert room info");
+
+        let found_info = rooms
+            .get_room_info("!fakeroom:example.com")
+            .expect("Error loading room info");
+
+        assert!(found_info.is_some());
+        assert_eq!(info, found_info.unwrap());
+    }
+
+    #[test]
+    fn get_room_info_none_when_room_does_not_exist() {
+        let rooms = create_test_instance();
+
+        let found_info = rooms
+            .get_room_info("!fakeroom:example.com")
+            .expect("Error loading room info");
+
+        assert!(found_info.is_none());
+    }
+
+    #[test]
+    fn clear_info_modifies_removes_requested_room() {
+        let rooms = create_test_instance();
+
+        rooms
+            .add_user_to_room("testuser", "myroom1")
+            .expect("Could not add user to room1");
+
+        rooms
+            .add_user_to_room("testuser", "myroom2")
+            .expect("Could not add user to room2");
+
+        rooms
+            .clear_info("myroom1")
+            .expect("Could not clear room info");
+
+        let users_in_room1 = rooms
+            .get_users_in_room("myroom1")
+            .expect("Could not retrieve users in room1");
+
+        let users_in_room2 = rooms
+            .get_users_in_room("myroom2")
+            .expect("Could not retrieve users in room2");
+
+        let rooms_for_user = rooms
+            .get_rooms_for_user("testuser")
+            .expect("Could not get rooms for user");
+
+        let expected_users_in_room2: HashSet<String> =
+            vec![String::from("testuser")].into_iter().collect();
+
+        let expected_rooms_for_user: HashSet<String> =
+            vec![String::from("myroom2")].into_iter().collect();
+
+        assert_eq!(HashSet::new(), users_in_room1);
+        assert_eq!(expected_users_in_room2, users_in_room2);
+        assert_eq!(expected_rooms_for_user, rooms_for_user);
+    }
+
+    #[test]
+    fn insert_to_timestamp_index() {
+        let rooms = create_test_instance();
+
+        // Insertion into timestamp index based on data that would go
+        // into main room x eventID -> timestamp tree.
+        let mut key = b"myroom".to_vec();
+        key.push(0xff);
+        key.extend_from_slice(b"myeventid");
+
+        let timestamp: U64<BigEndian> = U64::new(1000);
+
+        let result = timestamp_index::insert(
+            &rooms.roomtimestamp_eventid,
+            key.as_bytes(),
+            timestamp.as_bytes(),
+        );
+
+        assert!(result.is_ok());
+
+        // Retrieval of data from the timestamp index tree.
+        let mut ts_key = b"myroom".to_vec();
+        ts_key.push(0xff);
+        ts_key.extend_from_slice(timestamp.as_bytes());
+
+        let expected_events: HashSet<String> =
+            vec![String::from("myeventid")].into_iter().collect();
+
+        let event_ids = hashset_tree::get_set(&rooms.roomtimestamp_eventid, &ts_key)
+            .expect("Could not get set out of Tree");
+        assert_eq!(expected_events, event_ids);
+    }
+}
--- a/src/db/schema.rs
+++ b/src/db/schema.rs
@ -0,0 +1,52 @@
+use crate::db::errors::DataError;
+use byteorder::{BigEndian, LittleEndian};
+use zerocopy::byteorder::{I32, U32, U64};
+use zerocopy::LayoutVerified;
+
+/// User variables are stored as little-endian 32-bit integers in the
+/// database. This type alias makes the database code more pleasant to
+/// read.
+type LittleEndianI32Layout<'a> = LayoutVerified<&'a [u8], I32<LittleEndian>>;
+
+type LittleEndianU32Layout<'a> = LayoutVerified<&'a [u8], U32<LittleEndian>>;
+
+#[allow(dead_code)]
+type LittleEndianU64Layout<'a> = LayoutVerified<&'a [u8], U64<LittleEndian>>;
+
+type BigEndianU64Layout<'a> = LayoutVerified<&'a [u8], U64<BigEndian>>;
+
+/// Convert bytes to an i32 with zero-copy deserialization. An error
+/// is returned if the bytes do not represent an i32.
+pub(super) fn convert_i32(raw_value: &[u8]) -> Result<i32, DataError> {
+    let layout = LittleEndianI32Layout::new_unaligned(raw_value.as_ref());
+
+    if let Some(layout) = layout {
+        let value: I32<LittleEndian> = *layout;
+        Ok(value.get())
+    } else {
+        Err(DataError::I32SchemaViolation)
+    }
+}
+
+pub(super) fn convert_u32(raw_value: &[u8]) -> Result<u32, DataError> {
+    let layout = LittleEndianU32Layout::new_unaligned(raw_value.as_ref());
+
+    if let Some(layout) = layout {
+        let value: U32<LittleEndian> = *layout;
+        Ok(value.get())
+    } else {
+        Err(DataError::I32SchemaViolation)
+    }
+}
+
+#[allow(dead_code)]
+pub(super) fn convert_u64(raw_value: &[u8]) -> Result<u64, DataError> {
+    let layout = BigEndianU64Layout::new_unaligned(raw_value.as_ref());
+
+    if let Some(layout) = layout {
+        let value: U64<BigEndian> = *layout;
+        Ok(value.get())
+    } else {
+        Err(DataError::I32SchemaViolation)
+    }
+}
--- a/src/db/sqlite/errors.rs
+++ b/src/db/sqlite/errors.rs
@ -0,0 +1,72 @@
+use std::num::TryFromIntError;
+
+use sled::transaction::{TransactionError, UnabortableTransactionError};
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+pub enum DataError {
+    #[error("value does not exist for key: {0}")]
+    KeyDoesNotExist(String),
+
+    #[error("too many entries")]
+    TooManyEntries,
+
+    #[error("expected i32, but i32 schema was violated")]
+    I32SchemaViolation,
+
+    #[error("unexpected or corruptd data bytes")]
+    InvalidValue,
+
+    #[error("expected string ref, but utf8 schema was violated: {0}")]
+    Utf8RefSchemaViolation(#[from] std::str::Utf8Error),
+
+    #[error("expected string, but utf8 schema was violated: {0}")]
+    Utf8SchemaViolation(#[from] std::string::FromUtf8Error),
+
+    #[error("internal database error: {0}")]
+    InternalError(#[from] sled::Error),
+
+    #[error("transaction error: {0}")]
+    TransactionError(#[from] sled::transaction::TransactionError),
+
+    #[error("unabortable transaction error: {0}")]
+    UnabortableTransactionError(#[from] UnabortableTransactionError),
+
+    #[error("data migration error: {0}")]
+    MigrationError(#[from] super::migrator::MigrationError),
+
+    #[error("deserialization error: {0}")]
+    DeserializationError(#[from] bincode::Error),
+
+    #[error("sqlx error: {0}")]
+    SqlxError(#[from] sqlx::Error),
+
+    #[error("numeric conversion error")]
+    NumericConversionError(#[from] TryFromIntError),
+}
+
+/// This From implementation is necessary to deal with the recursive
+/// error type in the error enum. We defined a transaction error, but
+/// the only place we use it is when converting from
+/// sled::transaction::TransactionError<DataError>. This converter
+/// extracts the inner data error from transaction aborted errors, and
+/// forwards anything else onward as-is, but wrapped in DataError.
+impl From<TransactionError<DataError>> for DataError {
+    fn from(error: TransactionError<DataError>) -> Self {
+        match error {
+            TransactionError::Abort(data_err) => data_err,
+            TransactionError::Storage(storage_err) => {
+                DataError::TransactionError(TransactionError::Storage(storage_err))
+            }
+        }
+    }
+}
+
+/// Automatically aborts transactions that hit a DataError by using
+/// the try (question mark) operator when this trait implementation is
+/// in scope.
+impl From<DataError> for sled::transaction::ConflictableTransactionError<DataError> {
+    fn from(error: DataError) -> Self {
+        sled::transaction::ConflictableTransactionError::Abort(error)
+    }
+}
--- a/src/db/sqlite/migrator/migrations/V4__room_events.rs
+++ b/src/db/sqlite/migrator/migrations/V4__room_events.rs
@ -1,6 +1,5 @@
 use barrel::backend::Sqlite;
-use barrel::{types, Migration};
-
+use barrel::{types, types::Type, Migration};
 pub fn migration() -> String {
    let mut m = Migration::new();

--- a/src/db/sqlite/migrator/migrations/V5__room_users.rs
+++ b/src/db/sqlite/migrator/migrations/V5__room_users.rs
@ -1,5 +1,5 @@
 use barrel::backend::Sqlite;
-use barrel::{types, Migration};
+use barrel::{types, types::Type, Migration};

 pub fn migration() -> String {
    let mut m = Migration::new();
--- a/src/db/sqlite/mod.rs
+++ b/src/db/sqlite/mod.rs
@ -1,14 +1,80 @@
-use crate::db::errors::DataError;
+use async_trait::async_trait;
+use errors::DataError;
 use sqlx::sqlite::{SqliteConnectOptions, SqlitePool, SqlitePoolOptions};
 use sqlx::ConnectOptions;
 use std::clone::Clone;
+use std::collections::{HashMap, HashSet};
 use std::str::FromStr;

+use crate::models::RoomInfo;
+
+pub mod errors;
 pub mod migrator;
 pub mod rooms;
 pub mod state;
 pub mod variables;

+#[async_trait]
+pub(crate) trait DbState {
+    async fn get_device_id(&self) -> Result<Option<String>, DataError>;
+
+    async fn set_device_id(&self, device_id: &str) -> Result<(), DataError>;
+}
+
+#[async_trait]
+pub(crate) trait Rooms {
+    async fn should_process(&self, room_id: &str, event_id: &str) -> Result<bool, DataError>;
+
+    async fn insert_room_info(&self, info: &RoomInfo) -> Result<(), DataError>;
+
+    async fn get_room_info(&self, room_id: &str) -> Result<Option<RoomInfo>, DataError>;
+
+    async fn get_rooms_for_user(&self, user_id: &str) -> Result<HashSet<String>, DataError>;
+
+    async fn get_users_in_room(&self, room_id: &str) -> Result<HashSet<String>, DataError>;
+
+    async fn add_user_to_room(&self, username: &str, room_id: &str) -> Result<(), DataError>;
+
+    async fn remove_user_from_room(&self, username: &str, room_id: &str) -> Result<(), DataError>;
+
+    async fn clear_info(&self, room_id: &str) -> Result<(), DataError>;
+}
+
+// TODO move this up to the top once we delete sled. Traits will be the
+// main API, then we can have different impls for different DBs.
+#[async_trait]
+pub trait Variables {
+    async fn get_user_variables(
+        &self,
+        user: &str,
+        room_id: &str,
+    ) -> Result<HashMap<String, i32>, DataError>;
+
+    async fn get_variable_count(&self, user: &str, room_id: &str) -> Result<i32, DataError>;
+
+    async fn get_user_variable(
+        &self,
+        user: &str,
+        room_id: &str,
+        variable_name: &str,
+    ) -> Result<i32, DataError>;
+
+    async fn set_user_variable(
+        &self,
+        user: &str,
+        room_id: &str,
+        variable_name: &str,
+        value: i32,
+    ) -> Result<(), DataError>;
+
+    async fn delete_user_variable(
+        &self,
+        user: &str,
+        room_id: &str,
+        variable_name: &str,
+    ) -> Result<(), DataError>;
+}
+
 pub struct Database {
    conn: SqlitePool,
 }
--- a/src/db/sqlite/rooms.rs
+++ b/src/db/sqlite/rooms.rs
@ -1,9 +1,9 @@
-use super::Database;
-use crate::db::{errors::DataError, Rooms};
+use super::errors::DataError;
+use super::{Database, Rooms};
 use crate::models::RoomInfo;
 use async_trait::async_trait;
 use sqlx::SqlitePool;
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 use std::time::{SystemTime, UNIX_EPOCH};

 async fn record_event(conn: &SqlitePool, room_id: &str, event_id: &str) -> Result<(), DataError> {
@ -148,9 +148,8 @@ impl Rooms for Database {

 #[cfg(test)]
 mod tests {
+    use super::super::Rooms;
    use super::*;
-    use crate::db::sqlite::Database;
-    use crate::db::Rooms;

    async fn create_db() -> Database {
        let db_path = tempfile::NamedTempFile::new_in(".").unwrap();
--- a/src/db/sqlite/state.rs
+++ b/src/db/sqlite/state.rs
@ -1,5 +1,5 @@
-use super::Database;
-use crate::db::{errors::DataError, DbState};
+use super::errors::DataError;
+use super::{Database, DbState};
 use async_trait::async_trait;

 #[async_trait]
@ -35,8 +35,8 @@ impl DbState for Database {

 #[cfg(test)]
 mod tests {
-    use crate::db::sqlite::Database;
-    use crate::db::DbState;
+    use super::super::DbState;
+    use super::*;

    async fn create_db() -> Database {
        let db_path = tempfile::NamedTempFile::new_in(".").unwrap();
--- a/src/db/sqlite/variables.rs
+++ b/src/db/sqlite/variables.rs
@ -1,8 +1,13 @@
-use super::Database;
-use crate::db::{errors::DataError, Variables};
+use super::errors::DataError;
+use super::{Database, Variables};
 use async_trait::async_trait;
 use std::collections::HashMap;

+struct UserVariableRow {
+    key: String,
+    value: i32,
+}
+
 #[async_trait]
 impl Variables for Database {
    async fn get_user_variables(
@ -99,9 +104,8 @@ impl Variables for Database {

 #[cfg(test)]
 mod tests {
+    use super::super::Variables;
    use super::*;
-    use crate::db::sqlite::Database;
-    use crate::db::Variables;

    async fn create_db() -> Database {
        let db_path = tempfile::NamedTempFile::new_in(".").unwrap();
@ -116,6 +120,7 @@ mod tests {

    #[tokio::test(flavor = "multi_thread", worker_threads = 1)]
    async fn set_and_get_variable_test() {
+        use super::super::Variables;
        let db = create_db().await;

        db.set_user_variable("myuser", "myroom", "myvariable", 1)
@ -132,6 +137,7 @@ mod tests {

    #[tokio::test(flavor = "multi_thread", worker_threads = 1)]
    async fn get_missing_variable_test() {
+        use super::super::Variables;
        let db = create_db().await;

        let value = db.get_user_variable("myuser", "myroom", "myvariable").await;
@ -145,6 +151,7 @@ mod tests {

    #[tokio::test(flavor = "multi_thread", worker_threads = 1)]
    async fn get_other_user_variable_test() {
+        use super::super::Variables;
        let db = create_db().await;

        db.set_user_variable("myuser1", "myroom", "myvariable", 1)
--- a/src/db/state.rs
+++ b/src/db/state.rs
@ -0,0 +1,88 @@
+use crate::db::errors::DataError;
+use sled::Tree;
+
+#[derive(Clone)]
+pub struct DbState {
+    /// Tree of simple key-values for global state values that persist
+    /// between restarts (e.g. device ID).
+    pub(in crate::db) global_metadata: Tree,
+}
+
+const DEVICE_ID_KEY: &'static [u8] = b"device_id";
+
+impl DbState {
+    pub(in crate::db) fn new(db: &sled::Db) -> Result<DbState, sled::Error> {
+        Ok(DbState {
+            global_metadata: db.open_tree("global_metadata")?,
+        })
+    }
+
+    pub fn get_device_id(&self) -> Result<Option<String>, DataError> {
+        self.global_metadata
+            .get(DEVICE_ID_KEY)?
+            .map(|v| String::from_utf8(v.to_vec()))
+            .transpose()
+            .map_err(|e| e.into())
+    }
+
+    pub fn set_device_id(&self, device_id: &str) -> Result<(), DataError> {
+        self.global_metadata
+            .insert(DEVICE_ID_KEY, device_id.as_bytes())?;
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use sled::Config;
+
+    fn create_test_instance() -> DbState {
+        let config = Config::new().temporary(true);
+        let db = config.open().unwrap();
+        DbState::new(&db).unwrap()
+    }
+
+    #[test]
+    fn set_device_id_works() {
+        let state = create_test_instance();
+        let result = state.set_device_id("test-device");
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn set_device_id_can_overwrite() {
+        let state = create_test_instance();
+        state.set_device_id("test-device").expect("insert 1 failed");
+        let result = state.set_device_id("test-device2");
+        assert!(result.is_ok());
+    }
+
+    #[test]
+    fn get_device_id_returns_some_when_set() {
+        let state = create_test_instance();
+
+        state
+            .set_device_id("test-device")
+            .expect("could not store device id properly");
+
+        let device_id = state.get_device_id();
+
+        assert!(device_id.is_ok());
+
+        let device_id = device_id.unwrap();
+        assert!(device_id.is_some());
+        assert_eq!("test-device", device_id.unwrap());
+    }
+
+    #[test]
+    fn get_device_id_returns_none_when_unset() {
+        let state = create_test_instance();
+        let device_id = state.get_device_id();
+        assert!(device_id.is_ok());
+
+        let device_id = device_id.unwrap();
+        assert!(device_id.is_none());
+    }
+}
--- a/src/db/variables.rs
+++ b/src/db/variables.rs
@ -0,0 +1,410 @@
+use crate::db::errors::DataError;
+use crate::db::schema::convert_i32;
+use byteorder::LittleEndian;
+use sled::transaction::{abort, TransactionalTree};
+use sled::Transactional;
+use sled::Tree;
+use std::collections::HashMap;
+use std::convert::From;
+use std::str;
+use zerocopy::byteorder::I32;
+use zerocopy::AsBytes;
+
+use super::errors;
+
+pub(super) mod migrations;
+
+#[derive(Clone)]
+pub struct Variables {
+    //room id + username + variable = i32
+    pub(in crate::db) room_user_variables: Tree,
+
+    //room id + username = i32
+    pub(in crate::db) room_user_variable_count: Tree,
+}
+
+/// Request something by a username and room ID.
+pub struct UserAndRoom<'a>(pub &'a str, pub &'a str);
+
+fn to_vec(value: &UserAndRoom<'_>) -> Vec<u8> {
+    let mut bytes = vec![];
+    bytes.extend_from_slice(value.0.as_bytes());
+    bytes.push(0xfe);
+    bytes.extend_from_slice(value.1.as_bytes());
+    bytes
+}
+
+impl From<UserAndRoom<'_>> for Vec<u8> {
+    fn from(value: UserAndRoom) -> Vec<u8> {
+        to_vec(&value)
+    }
+}
+
+impl From<&UserAndRoom<'_>> for Vec<u8> {
+    fn from(value: &UserAndRoom) -> Vec<u8> {
+        to_vec(value)
+    }
+}
+
+/// Use a transaction to atomically alter the count of variables in
+/// the database by the given amount. Count cannot go below 0.
+fn alter_room_variable_count(
+    room_variable_count: &TransactionalTree,
+    user_and_room: &UserAndRoom<'_>,
+    amount: i32,
+) -> Result<i32, DataError> {
+    let key: Vec<u8> = user_and_room.into();
+
+    let mut new_count = match room_variable_count.get(&key)? {
+        Some(bytes) => convert_i32(&bytes)? + amount,
+        None => amount,
+    };
+
+    if new_count < 0 {
+        new_count = 0;
+    }
+
+    let db_value: I32<LittleEndian> = I32::new(new_count);
+    room_variable_count.insert(key, db_value.as_bytes())?;
+    Ok(new_count)
+}
+
+/// Room ID, Username, Variable Name
+pub type AllVariablesKey = (String, String, String);
+
+impl Variables {
+    pub(in crate::db) fn new(db: &sled::Db) -> Result<Variables, sled::Error> {
+        Ok(Variables {
+            room_user_variables: db.open_tree("variables")?,
+            room_user_variable_count: db.open_tree("room_user_variable_count")?,
+        })
+    }
+
+    pub fn get_all_variables(&self) -> Result<HashMap<AllVariablesKey, i32>, DataError> {
+        use std::convert::TryFrom;
+        let variables: Result<Vec<(AllVariablesKey, i32)>, DataError> = self
+            .room_user_variables
+            .scan_prefix("")
+            .map(|entry| match entry {
+                Ok((key, raw_value)) => {
+                    let keys: Vec<_> = key
+                        .split(|&b| b == 0xfe || b == 0xff)
+                        .map(|b| str::from_utf8(b))
+                        .collect();
+
+                    if let &[Ok(room_id), Ok(username), Ok(variable_name), ..] = keys.as_slice() {
+                        Ok((
+                            (
+                                room_id.to_owned(),
+                                username.to_owned(),
+                                variable_name.to_owned(),
+                            ),
+                            convert_i32(&raw_value)?,
+                        ))
+                    } else {
+                        Err(errors::DataError::InvalidValue)
+                    }
+                }
+                Err(e) => Err(e.into()),
+            })
+            .collect();
+
+        // Convert tuples to hash map with collect(), inferred via
+        // return type.
+        variables.map(|entries| entries.into_iter().collect())
+    }
+
+    pub fn get_user_variables(
+        &self,
+        key: &UserAndRoom<'_>,
+    ) -> Result<HashMap<String, i32>, DataError> {
+        let mut prefix: Vec<u8> = key.into();
+        prefix.push(0xff);
+        let prefix_len: usize = prefix.len();
+
+        let variables: Result<Vec<(String, i32)>, DataError> = self
+            .room_user_variables
+            .scan_prefix(prefix)
+            .map(|entry| match entry {
+                Ok((key, raw_value)) => {
+                    //Strips room and username from key, leaving behind name.
+                    let variable_name = str::from_utf8(&key[prefix_len..])?;
+                    Ok((variable_name.to_owned(), convert_i32(&raw_value)?))
+                }
+                Err(e) => Err(e.into()),
+            })
+            .collect();
+
+        // Convert tuples to hash map with collect(), inferred via
+        // return type.
+        variables.map(|entries| entries.into_iter().collect())
+    }
+
+    pub fn get_variable_count(&self, user_and_room: &UserAndRoom<'_>) -> Result<i32, DataError> {
+        let key: Vec<u8> = user_and_room.into();
+
+        match self.room_user_variable_count.get(&key)? {
+            Some(raw_value) => convert_i32(&raw_value),
+            None => Ok(0),
+        }
+    }
+
+    pub fn get_user_variable(
+        &self,
+        user_and_room: &UserAndRoom<'_>,
+        variable_name: &str,
+    ) -> Result<i32, DataError> {
+        let mut key: Vec<u8> = user_and_room.into();
+        key.push(0xff);
+        key.extend_from_slice(variable_name.as_bytes());
+
+        match self.room_user_variables.get(&key)? {
+            Some(raw_value) => convert_i32(&raw_value),
+            _ => Err(DataError::KeyDoesNotExist(variable_name.to_owned())),
+        }
+    }
+
+    pub fn set_user_variable(
+        &self,
+        user_and_room: &UserAndRoom<'_>,
+        variable_name: &str,
+        value: i32,
+    ) -> Result<(), DataError> {
+        if self.get_variable_count(user_and_room)? >= 100 {
+            return Err(DataError::TooManyEntries);
+        }
+
+        (&self.room_user_variables, &self.room_user_variable_count).transaction(
+            |(tx_vars, tx_counts)| {
+                let mut key: Vec<u8> = user_and_room.into();
+                key.push(0xff);
+                key.extend_from_slice(variable_name.as_bytes());
+
+                let db_value: I32<LittleEndian> = I32::new(value);
+                let old_value = tx_vars.insert(key, db_value.as_bytes())?;
+
+                //Only increment variable count on new keys.
+                if let None = old_value {
+                    if let Err(e) = alter_room_variable_count(&tx_counts, &user_and_room, 1) {
+                        return abort(e);
+                    }
+                }
+
+                Ok(())
+            },
+        )?;
+
+        Ok(())
+    }
+
+    pub fn delete_user_variable(
+        &self,
+        user_and_room: &UserAndRoom<'_>,
+        variable_name: &str,
+    ) -> Result<(), DataError> {
+        (&self.room_user_variables, &self.room_user_variable_count).transaction(
+            |(tx_vars, tx_counts)| {
+                let mut key: Vec<u8> = user_and_room.into();
+                key.push(0xff);
+                key.extend_from_slice(variable_name.as_bytes());
+
+                if let Some(_) = tx_vars.remove(key)? {
+                    if let Err(e) = alter_room_variable_count(&tx_counts, user_and_room, -1) {
+                        return abort(e);
+                    }
+                } else {
+                    return abort(DataError::KeyDoesNotExist(variable_name.to_owned()));
+                }
+
+                Ok(())
+            },
+        )?;
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use sled::Config;
+
+    fn create_test_instance() -> Variables {
+        let config = Config::new().temporary(true);
+        let db = config.open().unwrap();
+        Variables::new(&db).unwrap()
+    }
+
+    //Room Variable count tests
+
+    #[test]
+    fn alter_room_variable_count_test() {
+        let variables = create_test_instance();
+        let key = UserAndRoom("username", "room");
+
+        let alter_count = |amount: i32| {
+            variables
+                .room_user_variable_count
+                .transaction(|tx| match alter_room_variable_count(&tx, &key, amount) {
+                    Err(e) => abort(e),
+                    _ => Ok(()),
+                })
+                .expect("got transaction failure");
+        };
+
+        let get_count = |variables: &Variables| -> i32 {
+            variables
+                .get_variable_count(&key)
+                .expect("could not get variable count")
+        };
+
+        //addition
+        alter_count(5);
+        assert_eq!(5, get_count(&variables));
+
+        //subtraction
+        alter_count(-3);
+        assert_eq!(2, get_count(&variables));
+    }
+
+    #[test]
+    fn alter_room_variable_count_cannot_go_below_0_test() {
+        let variables = create_test_instance();
+        let key = UserAndRoom("username", "room");
+
+        variables
+            .room_user_variable_count
+            .transaction(|tx| match alter_room_variable_count(&tx, &key, -1000) {
+                Err(e) => abort(e),
+                _ => Ok(()),
+            })
+            .expect("got transaction failure");
+
+        let count = variables
+            .get_variable_count(&key)
+            .expect("could not get variable count");
+
+        assert_eq!(0, count);
+    }
+
+    #[test]
+    fn empty_db_reports_0_room_variable_count_test() {
+        let variables = create_test_instance();
+        let key = UserAndRoom("username", "room");
+
+        let count = variables
+            .get_variable_count(&key)
+            .expect("could not get variable count");
+
+        assert_eq!(0, count);
+    }
+
+    #[test]
+    fn set_user_variable_increments_count() {
+        let variables = create_test_instance();
+        let key = UserAndRoom("username", "room");
+
+        variables
+            .set_user_variable(&key, "myvariable", 5)
+            .expect("could not insert variable");
+
+        let count = variables
+            .get_variable_count(&key)
+            .expect("could not get variable count");
+
+        assert_eq!(1, count);
+    }
+
+    #[test]
+    fn update_user_variable_does_not_increment_count() {
+        let variables = create_test_instance();
+        let key = UserAndRoom("username", "room");
+
+        variables
+            .set_user_variable(&key, "myvariable", 5)
+            .expect("could not insert variable");
+
+        variables
+            .set_user_variable(&key, "myvariable", 10)
+            .expect("could not update variable");
+
+        let count = variables
+            .get_variable_count(&key)
+            .expect("could not get variable count");
+
+        assert_eq!(1, count);
+    }
+
+    // Set/get/delete variable tests
+
+    #[test]
+    fn set_and_get_variable_test() {
+        let variables = create_test_instance();
+        let key = UserAndRoom("username", "room");
+
+        variables
+            .set_user_variable(&key, "myvariable", 5)
+            .expect("could not insert variable");
+
+        let value = variables
+            .get_user_variable(&key, "myvariable")
+            .expect("could not get value");
+
+        assert_eq!(5, value);
+    }
+
+    #[test]
+    fn cannot_set_more_than_100_variables_per_room() {
+        let variables = create_test_instance();
+        let key = UserAndRoom("username", "room");
+
+        for c in 0..100 {
+            variables
+                .set_user_variable(&key, &format!("myvariable{}", c), 5)
+                .expect("could not insert variable");
+        }
+
+        let result = variables.set_user_variable(&key, "myvariable101", 5);
+        assert!(result.is_err());
+        assert!(matches!(result, Err(DataError::TooManyEntries)));
+    }
+
+    #[test]
+    fn delete_variable_test() {
+        let variables = create_test_instance();
+        let key = UserAndRoom("username", "room");
+
+        variables
+            .set_user_variable(&key, "myvariable", 5)
+            .expect("could not insert variable");
+
+        variables
+            .delete_user_variable(&key, "myvariable")
+            .expect("could not delete value");
+
+        let result = variables.get_user_variable(&key, "myvariable");
+
+        assert!(result.is_err());
+        assert!(matches!(result, Err(DataError::KeyDoesNotExist(_))));
+    }
+
+    #[test]
+    fn get_missing_variable_returns_key_does_not_exist() {
+        let variables = create_test_instance();
+        let key = UserAndRoom("username", "room");
+        let result = variables.get_user_variable(&key, "myvariable");
+
+        assert!(result.is_err());
+        assert!(matches!(result, Err(DataError::KeyDoesNotExist(_))));
+    }
+
+    #[test]
+    fn remove_missing_variable_returns_key_does_not_exist() {
+        let variables = create_test_instance();
+        let key = UserAndRoom("username", "room");
+        let result = variables.delete_user_variable(&key, "myvariable");
+
+        assert!(result.is_err());
+        assert!(matches!(result, Err(DataError::KeyDoesNotExist(_))));
+    }
+}
--- a/src/db/variables/migrations.rs
+++ b/src/db/variables/migrations.rs
@ -0,0 +1,354 @@
+use super::*;
+use crate::db::errors::{DataError, MigrationError};
+use crate::db::Database;
+use byteorder::LittleEndian;
+use memmem::{Searcher, TwoWaySearcher};
+use sled::transaction::TransactionError;
+use sled::{Batch, IVec};
+use std::collections::HashMap;
+use zerocopy::byteorder::{I32, U32};
+use zerocopy::AsBytes;
+
+pub(in crate::db) mod add_room_user_variable_count {
+    use super::*;
+    //Not to be confused with the super::RoomAndUser delineator.
+    #[derive(PartialEq, Eq, std::hash::Hash)]
+    struct RoomAndUser {
+        room_id: String,
+        username: String,
+    }
+
+    /// Create a version 0 user variable key.
+    fn v0_variable_key(info: &RoomAndUser, variable_name: &str) -> Vec<u8> {
+        let mut key = vec![];
+        key.extend_from_slice(info.room_id.as_bytes());
+        key.extend_from_slice(info.username.as_bytes());
+        key.extend_from_slice(variable_name.as_bytes());
+        key
+    }
+
+    fn map_value_to_room_and_user(
+        entry: sled::Result<(IVec, IVec)>,
+    ) -> Result<RoomAndUser, MigrationError> {
+        if let Ok((key, _)) = entry {
+            let keys: Vec<Result<&str, _>> = key
+                .split(|&b| b == 0xff)
+                .map(|b| str::from_utf8(b))
+                .collect();
+
+            if let &[_, Ok(room_id), Ok(username), Ok(_variable)] = keys.as_slice() {
+                Ok(RoomAndUser {
+                    room_id: room_id.to_owned(),
+                    username: username.to_owned(),
+                })
+            } else {
+                Err(MigrationError::MigrationFailed(
+                    "a key violates utf8 schema".to_string(),
+                ))
+            }
+        } else {
+            Err(MigrationError::MigrationFailed(
+                "encountered unexpected key".to_string(),
+            ))
+        }
+    }
+
+    fn create_key(room_id: &str, username: &str) -> Vec<u8> {
+        let mut key = b"variables".to_vec();
+        key.push(0xff);
+        key.extend_from_slice(room_id.as_bytes());
+        key.push(0xff);
+        key.extend_from_slice(username.as_bytes());
+        key.push(0xff);
+        key.extend_from_slice(b"variable_count");
+        key
+    }
+
+    pub(in crate::db) fn migrate(db: &Database) -> Result<(), DataError> {
+        let tree = &db.variables.room_user_variables;
+        let prefix = b"variables";
+
+        //Extract a vec of tuples, consisting of room id + username.
+        let results: Vec<RoomAndUser> = tree
+            .scan_prefix(prefix)
+            .map(map_value_to_room_and_user)
+            .collect::<Result<Vec<_>, MigrationError>>()?;
+
+        let counts: HashMap<RoomAndUser, u32> =
+            results
+                .into_iter()
+                .fold(HashMap::new(), |mut count_map, room_and_user| {
+                    let count = count_map.entry(room_and_user).or_insert(0);
+                    *count += 1;
+                    count_map
+                });
+
+        //Start a transaction on the variables tree.
+        let tx_result: Result<_, TransactionError<DataError>> =
+            db.variables.room_user_variables.transaction(|tx_vars| {
+                let batch = counts.iter().fold(Batch::default(), |mut batch, entry| {
+                    let (info, count) = entry;
+
+                    //Add variable count according to new schema.
+                    let key = create_key(&info.room_id, &info.username);
+                    let db_value: U32<LittleEndian> = U32::new(*count);
+                    batch.insert(key, db_value.as_bytes());
+
+                    //Delete the old variable_count variable if exists.
+                    let old_key = v0_variable_key(&info, "variable_count");
+                    batch.remove(old_key);
+                    batch
+                });
+
+                tx_vars.apply_batch(&batch)?;
+                Ok(())
+            });
+
+        tx_result?; //For some reason, it cannot infer the type
+        Ok(())
+    }
+}
+
+pub(in crate::db) fn delete_v0_schema(db: &Database) -> Result<(), DataError> {
+    let mut vars = db.variables.room_user_variables.scan_prefix("");
+    let mut batch = Batch::default();
+
+    while let Some(Ok((key, _))) = vars.next() {
+        let key = key.to_vec();
+
+        if !key.contains(&0xff) {
+            batch.remove(key);
+        }
+    }
+
+    db.variables.room_user_variables.apply_batch(batch)?;
+    Ok(())
+}
+
+pub(in crate::db) fn delete_variable_count(db: &Database) -> Result<(), DataError> {
+    let prefix = b"variables";
+    let mut vars = db.variables.room_user_variables.scan_prefix(prefix);
+    let mut batch = Batch::default();
+
+    while let Some(Ok((key, _))) = vars.next() {
+        let search = TwoWaySearcher::new(b"variable_count");
+        let ends_with = {
+            match search.search_in(&key) {
+                Some(index) => key.len() - index == b"variable_count".len(),
+                None => false,
+            }
+        };
+
+        if ends_with {
+            batch.remove(key);
+        }
+    }
+
+    db.variables.room_user_variables.apply_batch(batch)?;
+    Ok(())
+}
+
+pub(in crate::db) mod change_delineator_delimiter {
+    use super::*;
+
+    /// An entry in the room user variables keyspace.
+    struct UserVariableEntry {
+        room_id: String,
+        username: String,
+        variable_name: String,
+        value: IVec,
+    }
+
+    /// Extract keys and values from the variables keyspace according
+    /// to the v1 schema.
+    fn extract_v1_entries(
+        entry: sled::Result<(IVec, IVec)>,
+    ) -> Result<UserVariableEntry, MigrationError> {
+        if let Ok((key, value)) = entry {
+            let keys: Vec<Result<&str, _>> = key
+                .split(|&b| b == 0xff)
+                .map(|b| str::from_utf8(b))
+                .collect();
+
+            if let &[_, Ok(room_id), Ok(username), Ok(variable)] = keys.as_slice() {
+                Ok(UserVariableEntry {
+                    room_id: room_id.to_owned(),
+                    username: username.to_owned(),
+                    variable_name: variable.to_owned(),
+                    value: value,
+                })
+            } else {
+                Err(MigrationError::MigrationFailed(
+                    "a key violates utf8 schema".to_string(),
+                ))
+            }
+        } else {
+            Err(MigrationError::MigrationFailed(
+                "encountered unexpected key".to_string(),
+            ))
+        }
+    }
+
+    /// Create an old key, where delineator is separated by 0xff.
+    fn create_old_key(prefix: &[u8], insert: &UserVariableEntry) -> Vec<u8> {
+        let mut key = vec![];
+        key.extend_from_slice(&prefix); //prefix already has 0xff.
+        key.extend_from_slice(&insert.room_id.as_bytes());
+        key.push(0xff);
+        key.extend_from_slice(&insert.username.as_bytes());
+        key.push(0xff);
+        key.extend_from_slice(&insert.variable_name.as_bytes());
+        key
+    }
+
+    /// Create an old key, where delineator is separated by 0xfe.
+    fn create_new_key(prefix: &[u8], insert: &UserVariableEntry) -> Vec<u8> {
+        let mut key = vec![];
+        key.extend_from_slice(&prefix); //prefix already has 0xff.
+        key.extend_from_slice(&insert.room_id.as_bytes());
+        key.push(0xfe);
+        key.extend_from_slice(&insert.username.as_bytes());
+        key.push(0xff);
+        key.extend_from_slice(&insert.variable_name.as_bytes());
+        key
+    }
+
+    pub fn migrate(db: &Database) -> Result<(), DataError> {
+        let tree = &db.variables.room_user_variables;
+        let prefix = b"variables";
+
+        let results: Vec<UserVariableEntry> = tree
+            .scan_prefix(&prefix)
+            .map(extract_v1_entries)
+            .collect::<Result<Vec<_>, MigrationError>>()?;
+
+        let mut batch = Batch::default();
+
+        for insert in results {
+            let old = create_old_key(prefix, &insert);
+            let new = create_new_key(prefix, &insert);
+
+            batch.remove(old);
+            batch.insert(new, insert.value);
+        }
+
+        tree.apply_batch(batch)?;
+        Ok(())
+    }
+}
+
+/// Move the user variable entries into two tree structures, with yet
+/// another key format change. Now there is one tree for variable
+/// counts, and one tree for actual user variables. Keys in the user
+/// variable tree were changed to be username-first, then room ID.
+/// They are still separated by 0xfe, while the variable name is
+/// separated by 0xff. Variable count now stores just
+/// USERNAME0xfeROOM_ID and a count in its own tree. This enables
+/// public use of a strongly typed UserAndRoom struct for getting
+/// variables.
+pub(in crate::db) mod change_tree_structure {
+    use super::*;
+
+    /// An entry in the room user variables keyspace.
+    struct UserVariableEntry {
+        room_id: String,
+        username: String,
+        variable_name: String,
+        value: IVec,
+    }
+
+    /// Extract keys and values from the variables keyspace according
+    /// to the v1 schema.
+    fn extract_v1_entries(
+        entry: sled::Result<(IVec, IVec)>,
+    ) -> Result<UserVariableEntry, MigrationError> {
+        if let Ok((key, value)) = entry {
+            let keys: Vec<Result<&str, _>> = key
+                .split(|&b| b == 0xff || b == 0xfe)
+                .map(|b| str::from_utf8(b))
+                .collect();
+
+            if let &[_, Ok(room_id), Ok(username), Ok(variable)] = keys.as_slice() {
+                Ok(UserVariableEntry {
+                    room_id: room_id.to_owned(),
+                    username: username.to_owned(),
+                    variable_name: variable.to_owned(),
+                    value: value,
+                })
+            } else {
+                Err(MigrationError::MigrationFailed(
+                    "a key violates utf8 schema".to_string(),
+                ))
+            }
+        } else {
+            Err(MigrationError::MigrationFailed(
+                "encountered unexpected key".to_string(),
+            ))
+        }
+    }
+
+    /// Create an old key, of "variables" 0xff "room id" 0xfe "username" 0xff "variablename".
+    fn create_old_key(prefix: &[u8], insert: &UserVariableEntry) -> Vec<u8> {
+        let mut key = vec![];
+        key.extend_from_slice(&prefix); //prefix already has 0xff.
+        key.extend_from_slice(&insert.room_id.as_bytes());
+        key.push(0xff);
+        key.extend_from_slice(&insert.username.as_bytes());
+        key.push(0xff);
+        key.extend_from_slice(&insert.variable_name.as_bytes());
+        key
+    }
+
+    /// Create a new key, of "username" 0xfe "room id" 0xff "variablename".
+    fn create_new_key(insert: &UserVariableEntry) -> Vec<u8> {
+        let mut key = vec![];
+        key.extend_from_slice(&insert.username.as_bytes());
+        key.push(0xfe);
+        key.extend_from_slice(&insert.room_id.as_bytes());
+        key.push(0xff);
+        key.extend_from_slice(&insert.variable_name.as_bytes());
+        key
+    }
+
+    pub fn migrate(db: &Database) -> Result<(), DataError> {
+        let variables_tree = &db.variables.room_user_variables;
+        let count_tree = &db.variables.room_user_variable_count;
+        let prefix = b"variables";
+
+        let results: Vec<UserVariableEntry> = variables_tree
+            .scan_prefix(&prefix)
+            .map(extract_v1_entries)
+            .collect::<Result<Vec<_>, MigrationError>>()?;
+
+        let mut counts: HashMap<(String, String), i32> = HashMap::new();
+        let mut batch = Batch::default();
+
+        for insert in results {
+            let count = counts
+                .entry((insert.username.clone(), insert.room_id.clone()))
+                .or_insert(0);
+            *count += 1;
+
+            let old = create_old_key(prefix, &insert);
+            let new = create_new_key(&insert);
+
+            batch.remove(old);
+            batch.insert(new, insert.value);
+        }
+
+        let mut count_batch = Batch::default();
+        counts.into_iter().for_each(|((username, room_id), count)| {
+            let mut key = username.as_bytes().to_vec();
+            key.push(0xfe);
+            key.extend_from_slice(room_id.as_bytes());
+
+            let db_value: I32<LittleEndian> = I32::new(count);
+            count_batch.insert(key, db_value.as_bytes());
+        });
+
+        variables_tree.apply_batch(batch)?;
+        count_tree.apply_batch(count_batch)?;
+
+        Ok(())
+    }
+}
--- a/src/dice.rs
+++ b/src/dice.rs
@ -1,5 +1,6 @@
 use crate::context::Context;
-use crate::db::Variables;
+use crate::db::sqlite::Variables;
+use crate::db::variables::UserAndRoom;
 use crate::error::BotError;
 use crate::error::DiceRollingError;
 use crate::parser::Amount;
--- a/src/error.rs
+++ b/src/error.rs
@ -1,6 +1,6 @@
-use crate::commands::CommandError;
 use crate::config::ConfigError;
 use crate::db::errors::DataError;
+use crate::{commands::CommandError, db::sqlite::migrator};
 use thiserror::Error;

 #[derive(Error, Debug)]
@ -21,6 +21,9 @@ pub enum BotError {
    #[error("database error: {0}")]
    DataError(#[from] DataError),

+    #[error("sqlite database error: {0}")]
+    SqliteDataError(#[from] crate::db::sqlite::errors::DataError),
+
    #[error("the message should not be processed because it failed validation")]
    ShouldNotProcessError,

@ -70,6 +73,12 @@ pub enum BotError {
    #[error("variables not yet supported")]
    VariablesNotSupported,

+    #[error("database error")]
+    DatabaseError(#[from] sled::Error),
+
+    #[error("database migration error: {0}")]
+    SqliteError(#[from] migrator::MigrationError),
+
    #[error("too many commands or message was too large")]
    MessageTooLarge,

--- a/src/logic.rs
+++ b/src/logic.rs
@ -1,8 +1,9 @@
-use crate::db::Rooms;
+use crate::db::sqlite::errors::DataError;
+use crate::db::sqlite::Rooms;
 use crate::error::BotError;
 use crate::matrix;
 use crate::models::RoomInfo;
-use futures::stream::{self, StreamExt};
+use futures::stream::{self, StreamExt, TryStreamExt};
 use matrix_sdk::{self, identifiers::RoomId, Client};

 /// Record the information about a room, including users in it.