Merge pull request 'TypedTree' (#1456) from krtab/garage:typed_tree into main-v2

Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/1456
Reviewed-by: Armael <armael@noreply.localhost>
Reviewed-by: Alex <lx@deuxfleurs.fr>

src/api/admin/repair.rs

@@ -360,14 +360,7 @@ impl Worker for BlockRcRepair {
 		_must_exit: &mut watch::Receiver<bool>,
 	) -> Result<WorkerState, GarageError> {
 		for _i in 0..RC_REPAIR_ITER_COUNT {
-			let next1 = self
+			let next1 = self.block_manager.rc.get_first_hash_from(self.cursor)?;
-				.block_manager
-				.rc
-				.rc_table
-				.range(self.cursor.as_slice()..)?
-				.next()
-				.transpose()?
-				.map(|(k, _)| Hash::try_from(k.as_slice()).unwrap());
 			let next2 = self
 				.block_ref_table
 				.data

src/block/manager.rs

@@ -144,7 +144,7 @@ impl BlockManager {
 
 		// Open metadata tables
 		let rc = db
-			.open_tree("block_local_rc")
+			.open_typed_tree("block_local_rc")
 			.expect("Unable to open block_local_rc tree");
 		let rc = BlockRc::new(rc);
 
@@ -158,9 +158,9 @@ impl BlockManager {
 
 		let metrics = BlockManagerMetrics::new(
 			config.compression_level,
-			rc.rc_table.clone(),
+			rc.rc_table.untyped().clone(),
-			resync.queue.clone(),
+			resync.queue.untyped().clone(),
-			resync.errors.clone(),
+			resync.errors.untyped().clone(),
 			buffer_kb_semaphore.clone(),
 		);
 
@@ -449,9 +449,8 @@ impl BlockManager {
 		let mut blocks = Vec::with_capacity(self.resync.errors.approximate_len()?);
 		for ent in self.resync.errors.iter()? {
 			let (hash, cnt) = ent?;
-			let cnt = ErrorCounter::decode(&cnt);
 			blocks.push(BlockResyncErrorInfo {
-				hash: Hash::try_from(&hash).unwrap(),
+				hash,
 				refcount: 0,
 				error_count: cnt.errors,
 				last_try: cnt.last_try,

src/block/rc.rs

@@ -1,4 +1,5 @@
 use std::convert::TryInto;
+use std::num::NonZeroU64;
 
 use arc_swap::ArcSwapOption;
 
@@ -14,12 +15,12 @@ pub type CalculateRefcount =
 	Box<dyn Fn(&db::Transaction, &Hash) -> db::TxResult<usize, Error> + Send + Sync>;
 
 pub struct BlockRc {
-	pub rc_table: db::Tree,
+	pub(crate) rc_table: db::TypedTree<Hash, RcEntry>,
 	pub(crate) recalc_rc: ArcSwapOption<Vec<CalculateRefcount>>,
 }
 
 impl BlockRc {
-	pub(crate) fn new(rc: db::Tree) -> Self {
+	pub(crate) fn new(rc: db::TypedTree<Hash, RcEntry>) -> Self {
 		Self {
 			rc_table: rc,
 			recalc_rc: ArcSwapOption::new(None),
@@ -33,11 +34,8 @@ impl BlockRc {
 		tx: &mut db::Transaction,
 		hash: &Hash,
 	) -> db::TxOpResult<bool> {
-		let old_rc = RcEntry::parse_opt(tx.get(&self.rc_table, hash)?);
+		let old_rc = RcState(self.rc_table.tx_get(tx, hash)?);
-		match old_rc.increment().serialize() {
+		self.rc_table.tx_insert(tx, hash, &old_rc.increment())?;
-			Some(x) => tx.insert(&self.rc_table, hash, x)?,
-			None => unreachable!(),
-		}
 		Ok(old_rc.is_zero())
 	}
 
@@ -48,17 +46,27 @@ impl BlockRc {
 		tx: &mut db::Transaction,
 		hash: &Hash,
 	) -> db::TxOpResult<bool> {
-		let new_rc = RcEntry::parse_opt(tx.get(&self.rc_table, hash)?).decrement();
+		let new_rc = RcState(self.rc_table.tx_get(tx, hash)?).decrement();
-		match new_rc.serialize() {
+		match &new_rc.0 {
-			Some(x) => tx.insert(&self.rc_table, hash, x)?,
+			None => self.rc_table.tx_remove(tx, hash)?,
-			None => tx.remove(&self.rc_table, hash)?,
+			Some(rc) => self.rc_table.tx_insert(tx, hash, rc)?,
 		}
-		Ok(matches!(new_rc, RcEntry::Deletable { .. }))
+		Ok(matches!(new_rc.0, Some(RcEntry::Deletable { .. })))
 	}
 
-	/// Read a block's reference count
+	/// Read a block's reference counting state
-	pub(crate) fn get_block_rc(&self, hash: &Hash) -> Result<RcEntry, Error> {
+	pub(crate) fn get_block_rc(&self, hash: &Hash) -> Result<RcState, Error> {
-		Ok(RcEntry::parse_opt(self.rc_table.get(hash.as_ref())?))
+		Ok(RcState(self.rc_table.get(hash)?))
+	}
+
+	/// Return the first hash stored in the RC table at or after `cursor`
+	pub fn get_first_hash_from(&self, cursor: Hash) -> Result<Option<Hash>, Error> {
+		Ok(self
+			.rc_table
+			.range(cursor..)?
+			.next()
+			.transpose()?
+			.map(|(k, _)| k))
 	}
 
 	/// Delete an entry in the RC table if it is deletable and the
@@ -66,12 +74,11 @@ impl BlockRc {
 	pub(crate) fn clear_deleted_block_rc(&self, hash: &Hash) -> Result<(), Error> {
 		let now = now_msec();
 		self.rc_table.db().transaction(|tx| {
-			let rcval = RcEntry::parse_opt(tx.get(&self.rc_table, hash)?);
+			let rcval = self.rc_table.tx_get(tx, hash)?;
-			match rcval {
+			if let Some(RcEntry::Deletable { at_time }) = rcval {
-				RcEntry::Deletable { at_time } if now > at_time => {
+				if now > at_time {
-					tx.remove(&self.rc_table, hash)?;
+					self.rc_table.tx_remove(tx, hash)?;
 				}
-				_ => (),
 			}
 			Ok(())
 		})?;
@@ -91,28 +98,25 @@ impl BlockRc {
 					for f in recalc_fns.iter() {
 						cnt += f(tx, hash)?;
 					}
-					let old_rc = RcEntry::parse_opt(tx.get(&self.rc_table, hash)?);
+					let old_count = RcState(self.rc_table.tx_get(tx, hash)?).as_u64();
 					trace!(
 						"Block RC for {:?}: stored={}, calculated={}",
 						hash,
-						old_rc.as_u64(),
+						old_count,
 						cnt
 					);
-					if cnt as u64 != old_rc.as_u64() {
+					if cnt as u64 != old_count {
 						warn!(
 							"Fixing inconsistent block RC for {:?}: was {}, should be {}",
-							hash,
+							hash, old_count, cnt
-							old_rc.as_u64(),
-							cnt
 						);
-						let new_rc = if cnt > 0 {
+						let new_rc = match NonZeroU64::new(cnt as u64) {
-							RcEntry::Present { count: cnt as u64 }
+							Some(count) => RcEntry::Present { count },
-						} else {
+							None => RcEntry::Deletable {
-							RcEntry::Deletable {
 								at_time: now_msec() + BLOCK_GC_DELAY.as_millis() as u64,
-							}
+							},
 						};
-						tx.insert(&self.rc_table, hash, new_rc.serialize().unwrap())?;
+						self.rc_table.tx_insert(tx, hash, &new_rc)?;
 						Ok((cnt, true))
 					} else {
 						Ok((cnt, false))
@@ -131,13 +135,47 @@ impl BlockRc {
 	}
 }
 
-/// Describes the state of the reference counter for a block
+impl db::DbBytes for RcEntry {
+	fn encode(&self) -> Vec<u8> {
+		match self {
+			RcEntry::Present { count } => u64::to_be_bytes(count.get()).to_vec(),
+			RcEntry::Deletable { at_time } => {
+				[u64::to_be_bytes(0), u64::to_be_bytes(*at_time)].concat()
+			}
+		}
+	}
+
+	fn decode(bytes: &[u8]) -> std::result::Result<Self, db::DecodeError> {
+		if bytes.len() == 8 {
+			let count = NonZeroU64::new(u64::from_be_bytes(bytes.try_into().unwrap()))
+				.ok_or(db::DecodeError("invalid RC entry: zero count".into()))?;
+			Ok(RcEntry::Present { count })
+		} else if bytes.len() == 16 {
+			Ok(RcEntry::Deletable {
+				at_time: u64::from_be_bytes(bytes[8..16].try_into().unwrap()),
+			})
+		} else {
+			Err(db::DecodeError(
+				format!(
+					"invalid RC entry: expected 8 or 16 bytes, got {}",
+					bytes.len()
+				)
+				.into(),
+			))
+		}
+	}
+}
+
+/// A block's entry in the RC table.
+///
+/// A block with zero references and no pending deletion has no entry
+/// in the RC table at all: see [`RcState`].
 #[derive(Clone, Copy, Debug)]
 pub(crate) enum RcEntry {
-	/// Present: the block has `count` references, with `count` > 0.
+	/// Present: the block has `count` references.
 	///
 	/// This is stored as `u64::to_be_bytes(count)`
-	Present { count: u64 },
+	Present { count: NonZeroU64 },
 
 	/// Deletable: the block has zero references, and can be deleted
 	/// once time (returned by `now_msec`) is larger than `at_time`
@@ -147,72 +185,39 @@ pub(crate) enum RcEntry {
 	/// (this allows for the data format to be backwards compatible with
 	/// previous Garage versions that didn't have this intermediate state)
 	Deletable { at_time: u64 },
-
-	/// Absent: the block has zero references, and can be deleted
-	/// immediately
-	Absent,
 }
 
-impl RcEntry {
+/// Describes the state of the reference counter for a block: the block's
-	fn parse(bytes: &[u8]) -> Self {
+/// entry in the RC table, or `None` if it has none, meaning the block has
-		if bytes.len() == 8 {
+/// zero references and can be deleted immediately.
-			RcEntry::Present {
+#[derive(Clone, Copy, Debug)]
-				count: u64::from_be_bytes(bytes.try_into().unwrap()),
+pub(crate) struct RcState(Option<RcEntry>);
-			}
-		} else if bytes.len() == 16 {
-			RcEntry::Deletable {
-				at_time: u64::from_be_bytes(bytes[8..16].try_into().unwrap()),
-			}
-		} else {
-			panic!("Invalid RC entry: {:?}, database is corrupted. This is an error Garage is currently unable to recover from. Sorry, and also please report a bug.",
-				bytes
-			)
-		}
-	}
 
-	fn parse_opt<V: AsRef<[u8]>>(bytes: Option<V>) -> Self {
+impl RcState {
-		bytes
+	/// The new RC table entry after a reference is taken on the block
-			.map(|b| Self::parse(b.as_ref()))
+	fn increment(&self) -> RcEntry {
-			.unwrap_or(Self::Absent)
+		let count = match self.0 {
-	}
+			Some(RcEntry::Present { count }) => count.saturating_add(1),
-
+			_ => NonZeroU64::new(1).unwrap(),
-	fn serialize(self) -> Option<Vec<u8>> {
-		match self {
-			RcEntry::Present { count } => Some(u64::to_be_bytes(count).to_vec()),
-			RcEntry::Deletable { at_time } => {
-				Some([u64::to_be_bytes(0), u64::to_be_bytes(at_time)].concat())
-			}
-			RcEntry::Absent => None,
-		}
-	}
-
-	fn increment(self) -> Self {
-		let old_count = match self {
-			RcEntry::Present { count } => count,
-			_ => 0,
 		};
-		RcEntry::Present {
+		RcEntry::Present { count }
-			count: old_count + 1,
-		}
 	}
 
-	fn decrement(self) -> Self {
+	/// The new state after a reference to the block is dropped
-		match self {
+	fn decrement(&self) -> Self {
-			RcEntry::Present { count } => {
+		RcState(match self.0 {
-				if count > 1 {
+			Some(RcEntry::Present { count }) => Some(match NonZeroU64::new(count.get() - 1) {
-					RcEntry::Present { count: count - 1 }
+				Some(count) => RcEntry::Present { count },
-				} else {
+				None => RcEntry::Deletable {
-					RcEntry::Deletable {
+					at_time: now_msec() + BLOCK_GC_DELAY.as_millis() as u64,
-						at_time: now_msec() + BLOCK_GC_DELAY.as_millis() as u64,
+				},
-					}
+			}),
-				}
+			unchanged => unchanged,
-			}
+		})
-			del => del,
-		}
 	}
 
 	pub(crate) fn is_zero(&self) -> bool {
-		matches!(self, RcEntry::Deletable { .. } | RcEntry::Absent)
+		matches!(self.0, None | Some(RcEntry::Deletable { .. }))
 	}
 
 	pub(crate) fn is_nonzero(&self) -> bool {
@@ -220,10 +225,10 @@ impl RcEntry {
 	}
 
 	pub(crate) fn is_deletable(&self) -> bool {
-		match self {
+		match self.0 {
-			RcEntry::Present { .. } => false,
+			Some(RcEntry::Present { .. }) => false,
-			RcEntry::Deletable { at_time } => now_msec() > *at_time,
+			Some(RcEntry::Deletable { at_time }) => now_msec() > at_time,
-			RcEntry::Absent => true,
+			None => true,
 		}
 	}
 
@@ -232,8 +237,8 @@ impl RcEntry {
 	}
 
 	pub(crate) fn as_u64(&self) -> u64 {
-		match self {
+		match self.0 {
-			RcEntry::Present { count } => *count,
+			Some(RcEntry::Present { count }) => count.get(),
 			_ => 0,
 		}
 	}

src/block/repair.rs

@@ -102,16 +102,15 @@ impl Worker for RepairWorker {
 				let mut batch_of_hashes = vec![];
 				let start_bound = match self.next_start.as_ref() {
 					None => Bound::Unbounded,
-					Some(x) => Bound::Excluded(x.as_slice()),
+					Some(x) => Bound::Excluded(*x),
 				};
 				for entry in self
 					.manager
 					.rc
 					.rc_table
-					.range::<&[u8], _>((start_bound, Bound::Unbounded))?
+					.range((start_bound, Bound::Unbounded))?
 				{
 					let (hash, _) = entry?;
-					let hash = Hash::try_from(&hash[..]).unwrap();
 					batch_of_hashes.push(hash);
 					if batch_of_hashes.len() >= 1000 {
 						break;

src/block/resync.rs

@@ -44,15 +44,58 @@ pub(crate) const MAX_RESYNC_WORKERS: usize = 8;
 const INITIAL_RESYNC_TRANQUILITY: u32 = 2;
 
 pub struct BlockResyncManager {
-	pub(crate) queue: db::Tree,
+	pub(crate) queue: db::TypedTree<ResyncQueueKey, Hash>,
 	pub(crate) notify: Arc<Notify>,
-	pub(crate) errors: db::Tree,
+	pub(crate) errors: db::TypedTree<Hash, ErrorCounter>,
 
 	busy_set: BusySet,
 
 	persister: PersisterShared<ResyncPersistedConfig>,
 }
 
+/// Key of the resync queue tree: blocks are resynced in order of increasing
+/// `when` (msec timestamp of the next try), with the block hash as tie-breaker.
+///
+// CAREFUL: this type implements `DbOrdKey`, so its byte encoding must be
+// order-preserving.
+// The derived `Ord` compares fields in declaration order, which must match
+// the order in which `encode()` writes them; and `when` must remain an
+// *unsigned* integer, as the big-endian encoding is only order-preserving
+// for unsigned types.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub(crate) struct ResyncQueueKey {
+	pub(crate) when: u64,
+	pub(crate) hash: Hash,
+}
+
+impl db::DbBytes for ResyncQueueKey {
+	fn encode(&self) -> Vec<u8> {
+		let mut v = Vec::with_capacity(40);
+		v.extend_from_slice(&u64::to_be_bytes(self.when));
+		v.extend_from_slice(self.hash.as_slice());
+		v
+	}
+
+	fn decode(bytes: &[u8]) -> std::result::Result<Self, db::DecodeError> {
+		if bytes.len() != 40 {
+			return Err(db::DecodeError(
+				format!(
+					"invalid resync queue key: expected 40 bytes, got {}",
+					bytes.len()
+				)
+				.into(),
+			));
+		}
+		Ok(ResyncQueueKey {
+			when: u64::from_be_bytes(bytes[..8].try_into().unwrap()),
+			hash: Hash::try_from(&bytes[8..])
+				.ok_or_else(|| db::DecodeError("invalid resync queue key: bad hash".into()))?,
+		})
+	}
+}
+
+impl db::DbOrdKey for ResyncQueueKey {}
+
 #[derive(Serialize, Deserialize, Clone, Copy)]
 struct ResyncPersistedConfig {
 	n_workers: usize,
@@ -74,22 +117,21 @@ enum ResyncIterResult {
 	IdleFor(Duration),
 }
 
-type BusySet = Arc<Mutex<HashSet<Vec<u8>>>>;
+type BusySet = Arc<Mutex<HashSet<ResyncQueueKey>>>;
 
 struct BusyBlock {
-	time_bytes: Vec<u8>,
+	key: ResyncQueueKey,
-	hash_bytes: Vec<u8>,
 	busy_set: BusySet,
 }
 
 impl BlockResyncManager {
 	pub(crate) fn new(db: &db::Db, system: &System) -> Self {
 		let queue = db
-			.open_tree("block_local_resync_queue")
+			.open_typed_tree("block_local_resync_queue")
 			.expect("Unable to open block_local_resync_queue tree");
 
 		let errors = db
-			.open_tree("block_local_resync_errors")
+			.open_typed_tree("block_local_resync_errors")
 			.expect("Unable to open block_local_resync_errors tree");
 
 		let persister = PersisterShared::new(&system.metadata_dir, "resync_cfg");
@@ -116,11 +158,10 @@ impl BlockResyncManager {
 	/// Clear the error counter for a block and put it in queue immediately
 	pub fn clear_backoff(&self, hash: &Hash) -> Result<(), Error> {
 		let now = now_msec();
-		if let Some(ec) = self.errors.get(hash)? {
+		if let Some(mut ec) = self.errors.get(hash)? {
-			let mut ec = ErrorCounter::decode(&ec);
 			if ec.errors > 0 {
 				ec.last_try = now - ec.delay_msec();
-				self.errors.insert(hash, ec.encode())?;
+				self.errors.insert(hash, &ec)?;
 				self.put_to_resync_at(hash, now)?;
 				return Ok(());
 			}
@@ -251,23 +292,21 @@ impl BlockResyncManager {
 
 	pub(crate) fn put_to_resync_at(&self, hash: &Hash, when: u64) -> db::Result<()> {
 		trace!("Put resync_queue: {} {:?}", when, hash);
-		let mut key = u64::to_be_bytes(when).to_vec();
+		let qkey = ResyncQueueKey { when, hash: *hash };
-		key.extend(hash.as_ref());
+		self.queue.insert(&qkey, hash)?;
-		self.queue.insert(key, hash.as_ref())?;
 		self.notify.notify_waiters();
 		Ok(())
 	}
 
 	async fn resync_iter(&self, manager: &BlockManager) -> Result<ResyncIterResult, db::Error> {
 		if let Some(block) = self.get_block_to_resync()? {
-			let time_msec = u64::from_be_bytes(block.time_bytes[0..8].try_into().unwrap());
+			let time_msec = block.key.when;
 			let now = now_msec();
 
 			if now >= time_msec {
-				let hash = Hash::try_from(&block.hash_bytes[..]).unwrap();
+				let hash = block.key.hash;
 
-				if let Some(ec) = self.errors.get(hash.as_slice())? {
+				if let Some(ec) = self.errors.get(&hash)? {
-					let ec = ErrorCounter::decode(&ec);
 					if now < ec.next_try() {
 						// if next retry after an error is not yet,
 						// don't do resync and return early, but still
@@ -277,7 +316,7 @@ impl BlockResyncManager {
 						// is not removing the one we added just above
 						// (we want to do the remove after the insert to ensure
 						// that the item is not lost if we crash in-between)
-						self.queue.remove(&block.time_bytes)?;
+						self.queue.remove(&block.key)?;
 						return Ok(ResyncIterResult::BusyDidNothing);
 					}
 				}
@@ -307,21 +346,21 @@ impl BlockResyncManager {
 					manager.metrics.resync_error_counter.add(1);
 					error!("Error when resyncing {:?}: {}", hash, e);
 
-					let err_counter = match self.errors.get(hash.as_slice())? {
+					let err_counter = match self.errors.get(&hash)? {
-						Some(ec) => ErrorCounter::decode(&ec).add1(now + 1),
+						Some(ec) => ec.add1(now + 1),
 						None => ErrorCounter::new(now + 1),
 					};
 
-					self.errors.insert(hash.as_slice(), err_counter.encode())?;
+					self.errors.insert(&hash, &err_counter)?;
 
 					self.put_to_resync_at(&hash, err_counter.next_try())?;
 					// err_counter.next_try() >= now + 1 > now,
 					// the entry we remove from the queue is not
 					// the entry we inserted with put_to_resync_at
-					self.queue.remove(&block.time_bytes)?;
+					self.queue.remove(&block.key)?;
 				} else {
-					self.errors.remove(hash.as_slice())?;
+					self.errors.remove(&hash)?;
-					self.queue.remove(&block.time_bytes)?;
+					self.queue.remove(&block.key)?;
 				}
 
 				Ok(ResyncIterResult::BusyDidSomething)
@@ -344,12 +383,11 @@ impl BlockResyncManager {
 	fn get_block_to_resync(&self) -> Result<Option<BusyBlock>, db::Error> {
 		let mut busy = self.busy_set.lock().unwrap();
 		for it in self.queue.iter()? {
-			let (time_bytes, hash_bytes) = it?;
+			let (key, _) = it?;
-			if !busy.contains(&time_bytes) {
+			if !busy.contains(&key) {
-				busy.insert(time_bytes.clone());
+				busy.insert(key);
 				return Ok(Some(BusyBlock {
-					time_bytes,
+					key,
-					hash_bytes,
 					busy_set: self.busy_set.clone(),
 				}));
 			}
@@ -506,7 +544,7 @@ impl BlockResyncManager {
 impl Drop for BusyBlock {
 	fn drop(&mut self) {
 		let mut busy = self.busy_set.lock().unwrap();
-		busy.remove(&self.time_bytes);
+		busy.remove(&self.key);
 	}
 }
 
@@ -516,6 +554,7 @@ pub(crate) struct ResyncWorker {
 	tranquilizer: Tranquilizer,
 	next_delay: Duration,
 	persister: PersisterShared<ResyncPersistedConfig>,
+	had_decode_error: bool,
 }
 
 impl ResyncWorker {
@@ -527,6 +566,7 @@ impl ResyncWorker {
 			tranquilizer: Tranquilizer::new(30),
 			next_delay: Duration::from_secs(10),
 			persister,
+			had_decode_error: false,
 		}
 	}
 }
@@ -574,6 +614,15 @@ impl Worker for ResyncWorker {
 				self.next_delay = delay;
 				Ok(WorkerState::Idle)
 			}
+			Err(db::Error::Decode(e)) => {
+				// We give it one second chance in the very unlikely case that the bytes would somehow
+				// have been corrupted during read and that a new read would lead to a correct decoding.
+				if self.had_decode_error {
+					panic!("An error has happened when decoding something stored in the local k/v store: {}.", e);
+				}
+				self.had_decode_error = true;
+				Ok(WorkerState::Busy)
+			}
 			Err(e) => {
 				// The errors that we have here are only db errors
 				// We don't really know how to handle them so just ¯\_(ツ)_/¯
@@ -581,6 +630,7 @@ impl Worker for ResyncWorker {
 				// if it does there is not much we can do -- TODO should we just panic?)
 				// Here we just give the error to the worker manager,
 				// it will print it to the logs and increment a counter
+				self.had_decode_error = false;
 				Err(e.into())
 			}
 		}
@@ -602,6 +652,7 @@ impl Worker for ResyncWorker {
 
 /// Counts the number of errors when resyncing a block,
 /// and the time of the last try.
+///
 /// Used to implement exponential backoff.
 #[derive(Clone, Copy, Debug)]
 pub(crate) struct ErrorCounter {
@@ -609,6 +660,31 @@ pub(crate) struct ErrorCounter {
 	pub(crate) last_try: u64,
 }
 
+impl db::DbBytes for ErrorCounter {
+	fn encode(&self) -> Vec<u8> {
+		let mut v = Vec::with_capacity(16);
+		v.extend_from_slice(&u64::to_be_bytes(self.errors));
+		v.extend_from_slice(&u64::to_be_bytes(self.last_try));
+		v
+	}
+
+	fn decode(bytes: &[u8]) -> std::result::Result<Self, db::DecodeError> {
+		if bytes.len() != 16 {
+			return Err(db::DecodeError(
+				format!(
+					"invalid error counter: expected 16 bytes, got {}",
+					bytes.len()
+				)
+				.into(),
+			));
+		}
+		Ok(Self {
+			errors: u64::from_be_bytes(bytes[..8].try_into().unwrap()),
+			last_try: u64::from_be_bytes(bytes[8..].try_into().unwrap()),
+		})
+	}
+}
+
 impl ErrorCounter {
 	fn new(now: u64) -> Self {
 		Self {
@@ -617,21 +693,6 @@ impl ErrorCounter {
 		}
 	}
 
-	pub(crate) fn decode(data: &[u8]) -> Self {
-		Self {
-			errors: u64::from_be_bytes(data[0..8].try_into().unwrap()),
-			last_try: u64::from_be_bytes(data[8..16].try_into().unwrap()),
-		}
-	}
-
-	fn encode(&self) -> Vec<u8> {
-		[
-			u64::to_be_bytes(self.errors),
-			u64::to_be_bytes(self.last_try),
-		]
-		.concat()
-	}
-
 	fn add1(self, now: u64) -> Self {
 		Self {
 			errors: self.errors + 1,

src/db/fjall_adapter.rs

@@ -12,7 +12,7 @@ use fjall::{
 
 use crate::{
 	open::{Engine, OpenOpt},
-	Db, Error, IDb, ITx, ITxFn, OnCommit, Result, TxError, TxFnResult, TxOpError, TxOpResult,
+	Db, DbError, DbResult, Error, IDb, ITx, ITxFn, OnCommit, TxError, TxFnResult, TxOpError,
 	TxResult, TxValueIter, Value, ValueIter,
 };
 
@@ -20,10 +20,10 @@ pub use fjall;
 
 // --
 
-pub(crate) fn open_db(path: &Path, opt: &OpenOpt) -> Result<Db> {
+pub(crate) fn open_db(path: &Path, opt: &OpenOpt) -> DbResult<Db> {
 	info!("Opening Fjall database at: {}", path.display());
 	if opt.fsync {
-		return Err(Error(
+		return Err(DbError(
 			"metadata_fsync is not supported with the Fjall database engine".into(),
 		));
 	}
@@ -37,21 +37,27 @@ pub(crate) fn open_db(path: &Path, opt: &OpenOpt) -> Result<Db> {
 
 // -- err
 
-impl From<fjall::Error> for Error {
+impl From<fjall::Error> for DbError {
-	fn from(e: fjall::Error) -> Error {
+	fn from(e: fjall::Error) -> DbError {
-		Error(format!("fjall: {}", e).into())
+		DbError(format!("fjall: {}", e).into())
 	}
 }
 
-impl From<fjall::LsmError> for Error {
+impl From<fjall::LsmError> for DbError {
-	fn from(e: fjall::LsmError) -> Error {
+	fn from(e: fjall::LsmError) -> DbError {
-		Error(format!("fjall lsm_tree: {}", e).into())
+		DbError(format!("fjall lsm_tree: {}", e).into())
+	}
+}
+
+impl From<fjall::Error> for Error {
+	fn from(e: fjall::Error) -> Error {
+		Error::Db(DbError::from(e))
 	}
 }
 
 impl From<fjall::Error> for TxOpError {
 	fn from(e: fjall::Error) -> TxOpError {
-		TxOpError(e.into())
+		DbError::from(e).into()
 	}
 }
 
@@ -76,11 +82,11 @@ impl FjallDb {
 	fn get_tree(
 		&self,
 		i: usize,
-	) -> Result<MappedRwLockReadGuard<'_, TransactionalPartitionHandle>> {
+	) -> DbResult<MappedRwLockReadGuard<'_, TransactionalPartitionHandle>> {
 		RwLockReadGuard::try_map(self.trees.read(), |trees: &Vec<_>| {
 			trees.get(i).map(|tup| &tup.1)
 		})
-		.map_err(|_| Error("invalid tree id".into()))
+		.map_err(|_| DbError("invalid tree id".into()))
 	}
 }
 
@@ -89,7 +95,7 @@ impl IDb for FjallDb {
 		"Fjall (EXPERIMENTAL!)".into()
 	}
 
-	fn open_tree(&self, name: &str) -> Result<usize> {
+	fn open_tree(&self, name: &str) -> DbResult<usize> {
 		let mut trees = self.trees.write();
 		let safe_name = encode_name(name)?;
 		if let Some(i) = trees.iter().position(|(name, _)| *name == safe_name) {
@@ -104,15 +110,15 @@ impl IDb for FjallDb {
 		}
 	}
 
-	fn list_trees(&self) -> Result<Vec<String>> {
+	fn list_trees(&self) -> DbResult<Vec<String>> {
 		self.keyspace
 			.list_partitions()
 			.iter()
 			.map(|n| decode_name(n))
-			.collect::<Result<Vec<_>>>()
+			.collect::<DbResult<Vec<_>>>()
 	}
 
-	fn snapshot(&self, base_path: &Path) -> Result<()> {
+	fn snapshot(&self, base_path: &Path) -> DbResult<()> {
 		std::fs::create_dir_all(base_path)?;
 		let path = Engine::Fjall.db_path(base_path);
 
@@ -138,7 +144,7 @@ impl IDb for FjallDb {
 
 	// ----
 
-	fn get(&self, tree_idx: usize, key: &[u8]) -> Result<Option<Value>> {
+	fn get(&self, tree_idx: usize, key: &[u8]) -> DbResult<Option<Value>> {
 		let tree = self.get_tree(tree_idx)?;
 		let tx = self.keyspace.read_tx();
 		let val = tx.get(&tree, key)?;
@@ -148,17 +154,17 @@ impl IDb for FjallDb {
 		}
 	}
 
-	fn approximate_len(&self, tree_idx: usize) -> Result<usize> {
+	fn approximate_len(&self, tree_idx: usize) -> DbResult<usize> {
 		let tree = self.get_tree(tree_idx)?;
 		Ok(tree.approximate_len())
 	}
-	fn is_empty(&self, tree_idx: usize) -> Result<bool> {
+	fn is_empty(&self, tree_idx: usize) -> DbResult<bool> {
 		let tree = self.get_tree(tree_idx)?;
 		let tx = self.keyspace.read_tx();
 		Ok(tx.is_empty(&tree)?)
 	}
 
-	fn insert(&self, tree_idx: usize, key: &[u8], value: &[u8]) -> Result<()> {
+	fn insert(&self, tree_idx: usize, key: &[u8], value: &[u8]) -> DbResult<()> {
 		let tree = self.get_tree(tree_idx)?;
 		let mut tx = self.keyspace.write_tx();
 		tx.insert(&tree, key, value);
@@ -166,7 +172,7 @@ impl IDb for FjallDb {
 		Ok(())
 	}
 
-	fn remove(&self, tree_idx: usize, key: &[u8]) -> Result<()> {
+	fn remove(&self, tree_idx: usize, key: &[u8]) -> DbResult<()> {
 		let tree = self.get_tree(tree_idx)?;
 		let mut tx = self.keyspace.write_tx();
 		tx.remove(&tree, key);
@@ -174,11 +180,11 @@ impl IDb for FjallDb {
 		Ok(())
 	}
 
-	fn clear(&self, tree_idx: usize) -> Result<()> {
+	fn clear(&self, tree_idx: usize) -> DbResult<()> {
 		let mut trees = self.trees.write();
 
 		if tree_idx >= trees.len() {
-			return Err(Error("invalid tree id".into()));
+			return Err(DbError("invalid tree id".into()));
 		}
 		let (name, tree) = trees.remove(tree_idx);
 
@@ -191,13 +197,13 @@ impl IDb for FjallDb {
 		Ok(())
 	}
 
-	fn iter(&self, tree_idx: usize) -> Result<ValueIter<'_>> {
+	fn iter(&self, tree_idx: usize) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree_idx)?;
 		let tx = self.keyspace.read_tx();
 		Ok(Box::new(tx.iter(&tree).map(iterator_remap)))
 	}
 
-	fn iter_rev(&self, tree_idx: usize) -> Result<ValueIter<'_>> {
+	fn iter_rev(&self, tree_idx: usize) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree_idx)?;
 		let tx = self.keyspace.read_tx();
 		Ok(Box::new(tx.iter(&tree).rev().map(iterator_remap)))
@@ -208,7 +214,7 @@ impl IDb for FjallDb {
 		tree_idx: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'_>> {
+	) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree_idx)?;
 		let tx = self.keyspace.read_tx();
 		Ok(Box::new(
@@ -221,7 +227,7 @@ impl IDb for FjallDb {
 		tree_idx: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'_>> {
+	) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree_idx)?;
 		let tx = self.keyspace.read_tx();
 		Ok(Box::new(
@@ -252,9 +258,9 @@ impl IDb for FjallDb {
 			}
 			TxFnResult::DbErr => {
 				tx.tx.rollback();
-				Err(TxError::Db(Error(
+				Err(TxError::Db(
-					"(this message will be discarded)".into(),
+					DbError("(this message will be discarded)".into()).into(),
-				)))
+				))
 			}
 		}
 	}
@@ -268,47 +274,47 @@ struct FjallTx<'a> {
 }
 
 impl<'a> FjallTx<'a> {
-	fn get_tree(&self, i: usize) -> TxOpResult<&TransactionalPartitionHandle> {
+	fn get_tree(&self, i: usize) -> DbResult<&TransactionalPartitionHandle> {
 		self.trees.get(i).map(|tup| &tup.1).ok_or_else(|| {
-			TxOpError(Error(
+			DbError(
 				"invalid tree id (it might have been opened after the transaction started)".into(),
-			))
+			)
 		})
 	}
 }
 
 impl<'a> ITx for FjallTx<'a> {
-	fn get(&self, tree_idx: usize, key: &[u8]) -> TxOpResult<Option<Value>> {
+	fn get(&self, tree_idx: usize, key: &[u8]) -> DbResult<Option<Value>> {
 		let tree = self.get_tree(tree_idx)?;
 		match self.tx.get(tree, key)? {
 			Some(v) => Ok(Some(v.to_vec())),
 			None => Ok(None),
 		}
 	}
-	fn len(&self, tree_idx: usize) -> TxOpResult<usize> {
+	fn len(&self, tree_idx: usize) -> DbResult<usize> {
 		let tree = self.get_tree(tree_idx)?;
 		Ok(self.tx.len(tree)?)
 	}
 
-	fn insert(&mut self, tree_idx: usize, key: &[u8], value: &[u8]) -> TxOpResult<()> {
+	fn insert(&mut self, tree_idx: usize, key: &[u8], value: &[u8]) -> DbResult<()> {
 		let tree = self.get_tree(tree_idx)?.clone();
 		self.tx.insert(&tree, key, value);
 		Ok(())
 	}
-	fn remove(&mut self, tree_idx: usize, key: &[u8]) -> TxOpResult<()> {
+	fn remove(&mut self, tree_idx: usize, key: &[u8]) -> DbResult<()> {
 		let tree = self.get_tree(tree_idx)?.clone();
 		self.tx.remove(&tree, key);
 		Ok(())
 	}
-	fn clear(&mut self, _tree_idx: usize) -> TxOpResult<()> {
+	fn clear(&mut self, _tree_idx: usize) -> DbResult<()> {
 		unimplemented!("LSM tree clearing in cross-partition transaction is not supported")
 	}
 
-	fn iter(&self, tree_idx: usize) -> TxOpResult<TxValueIter<'_>> {
+	fn iter(&self, tree_idx: usize) -> DbResult<TxValueIter<'_>> {
 		let tree = self.get_tree(tree_idx)?.clone();
 		Ok(Box::new(self.tx.iter(&tree).map(iterator_remap_tx)))
 	}
-	fn iter_rev(&self, tree_idx: usize) -> TxOpResult<TxValueIter<'_>> {
+	fn iter_rev(&self, tree_idx: usize) -> DbResult<TxValueIter<'_>> {
 		let tree = self.get_tree(tree_idx)?.clone();
 		Ok(Box::new(self.tx.iter(&tree).rev().map(iterator_remap_tx)))
 	}
@@ -318,7 +324,7 @@ impl<'a> ITx for FjallTx<'a> {
 		tree_idx: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> TxOpResult<TxValueIter<'_>> {
+	) -> DbResult<TxValueIter<'_>> {
 		let tree = self.get_tree(tree_idx)?;
 		let low = clone_bound(low);
 		let high = clone_bound(high);
@@ -333,7 +339,7 @@ impl<'a> ITx for FjallTx<'a> {
 		tree_idx: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> TxOpResult<TxValueIter<'_>> {
+	) -> DbResult<TxValueIter<'_>> {
 		let tree = self.get_tree(tree_idx)?;
 		let low = clone_bound(low);
 		let high = clone_bound(high);
@@ -348,14 +354,14 @@ impl<'a> ITx for FjallTx<'a> {
 
 // -- maps fjall's (k, v) to ours
 
-fn iterator_remap(r: fjall::Result<(fjall::Slice, fjall::Slice)>) -> Result<(Value, Value)> {
+fn iterator_remap(r: fjall::Result<(fjall::Slice, fjall::Slice)>) -> DbResult<(Value, Value)> {
 	r.map(|(k, v)| (k.to_vec(), v.to_vec()))
-		.map_err(|e| e.into())
+		.map_err(DbError::from)
 }
 
-fn iterator_remap_tx(r: fjall::Result<(fjall::Slice, fjall::Slice)>) -> TxOpResult<(Value, Value)> {
+fn iterator_remap_tx(r: fjall::Result<(fjall::Slice, fjall::Slice)>) -> DbResult<(Value, Value)> {
 	r.map(|(k, v)| (k.to_vec(), v.to_vec()))
-		.map_err(|e| e.into())
+		.map_err(DbError::from)
 }
 
 // -- utils to deal with Garage's tightness on Bound lifetimes
@@ -378,7 +384,7 @@ fn clone_bound(bound: Bound<&[u8]>) -> ByteVecBound {
 
 // -- utils to encode table names --
 
-fn encode_name(s: &str) -> Result<String> {
+fn encode_name(s: &str) -> DbResult<String> {
 	let base = 'A' as u32;
 
 	let mut ret = String::with_capacity(s.len() + 10);
@@ -392,7 +398,7 @@ fn encode_name(s: &str) -> Result<String> {
 			ret.push(char::from_u32(base + c_hi).unwrap());
 			ret.push(char::from_u32(base + c_lo).unwrap());
 		} else {
-			return Err(Error(
+			return Err(DbError(
 				format!("table name {} could not be safely encoded", s).into(),
 			));
 		}
@@ -400,10 +406,10 @@ fn encode_name(s: &str) -> Result<String> {
 	Ok(ret)
 }
 
-fn decode_name(s: &str) -> Result<String> {
+fn decode_name(s: &str) -> DbResult<String> {
 	use std::convert::TryFrom;
 
-	let errfn = || Error(format!("encoded table name {} is invalid", s).into());
+	let errfn = || DbError(format!("encoded table name {} is invalid", s).into());
 	let c_map = |c: char| {
 		let c = c as u32;
 		let base = 'A' as u32;

src/db/lib.rs

@@ -9,6 +9,7 @@ pub mod lmdb_adapter;
 pub mod sqlite_adapter;
 
 pub mod open;
+pub mod typed;
 
 #[cfg(test)]
 pub mod test;
@@ -23,6 +24,7 @@ use std::sync::Arc;
 use thiserror::Error;
 
 pub use open::*;
+pub use typed::{DbBytes, DbOrdKey, TypedIter, TypedTree, TypedTxIter};
 
 pub(crate) type OnCommit = Vec<Box<dyn FnOnce()>>;
 
@@ -38,21 +40,34 @@ pub struct Transaction<'a> {
 pub struct Tree(Arc<dyn IDb>, usize);
 
 pub type Value = Vec<u8>;
-pub type ValueIter<'a> = Box<dyn std::iter::Iterator<Item = Result<(Value, Value)>> + 'a>;
+pub type ValueIter<'a> = Box<dyn std::iter::Iterator<Item = DbResult<(Value, Value)>> + 'a>;
-pub type TxValueIter<'a> = Box<dyn std::iter::Iterator<Item = TxOpResult<(Value, Value)>> + 'a>;
+pub type TxValueIter<'a> = Box<dyn std::iter::Iterator<Item = DbResult<(Value, Value)>> + 'a>;
 
 // ----
 
 #[derive(Debug, Error)]
-#[error("{0}")]
+#[error("database error: {0}")]
-pub struct Error(pub Cow<'static, str>);
+pub struct DbError(pub Cow<'static, str>);
 
-impl From<std::io::Error> for Error {
+#[derive(Debug, Error)]
-	fn from(e: std::io::Error) -> Error {
+#[error("decode error: {0}")]
-		Error(format!("IO: {}", e).into())
+pub struct DecodeError(pub Cow<'static, str>);
+
+#[derive(Debug, Error)]
+pub enum Error {
+	#[error(transparent)]
+	Db(#[from] DbError),
+	#[error(transparent)]
+	Decode(#[from] DecodeError),
+}
+
+impl From<std::io::Error> for DbError {
+	fn from(e: std::io::Error) -> DbError {
+		DbError(format!("IO: {}", e).into())
 	}
 }
 
+pub type DbResult<T> = std::result::Result<T, DbError>;
 pub type Result<T> = std::result::Result<T, Error>;
 
 #[derive(Debug, Error)]
@@ -60,6 +75,18 @@ pub type Result<T> = std::result::Result<T, Error>;
 pub struct TxOpError(pub(crate) Error);
 pub type TxOpResult<T> = std::result::Result<T, TxOpError>;
 
+impl From<DbError> for TxOpError {
+	fn from(e: DbError) -> TxOpError {
+		TxOpError(e.into())
+	}
+}
+
+impl From<DecodeError> for TxOpError {
+	fn from(e: DecodeError) -> TxOpError {
+		TxOpError(e.into())
+	}
+}
+
 #[derive(Debug)]
 pub enum TxError<E> {
 	Abort(E),
@@ -73,6 +100,12 @@ impl<E> From<TxOpError> for TxError<E> {
 	}
 }
 
+impl<E> From<DbError> for TxError<E> {
+	fn from(e: DbError) -> TxError<E> {
+		TxError::Db(e.into())
+	}
+}
+
 pub fn unabort<R, E>(res: TxResult<R, E>) -> TxOpResult<std::result::Result<R, E>> {
 	match res {
 		Ok(v) => Ok(Ok(v)),
@@ -88,12 +121,12 @@ impl Db {
 		self.0.engine()
 	}
 
-	pub fn open_tree<S: AsRef<str>>(&self, name: S) -> Result<Tree> {
+	pub fn open_tree<S: AsRef<str>>(&self, name: S) -> DbResult<Tree> {
 		let tree_id = self.0.open_tree(name.as_ref())?;
 		Ok(Tree(self.0.clone(), tree_id))
 	}
 
-	pub fn list_trees(&self) -> Result<Vec<String>> {
+	pub fn list_trees(&self) -> DbResult<Vec<String>> {
 		self.0.list_trees()
 	}
 
@@ -147,27 +180,28 @@ impl Db {
 		}
 	}
 
-	pub fn snapshot(&self, path: &Path) -> Result<()> {
+	pub fn snapshot(&self, path: &Path) -> DbResult<()> {
 		self.0.snapshot(path)
 	}
 
 	pub fn import(&self, other: &Db) -> Result<()> {
 		let existing_trees = self.list_trees()?;
 		if !existing_trees.is_empty() {
-			return Err(Error(
+			return Err(DbError(
 				format!(
 					"destination database already contains data: {:?}",
 					existing_trees
 				)
 				.into(),
-			));
+			)
+			.into());
 		}
 
 		let tree_names = other.list_trees()?;
 		for name in tree_names {
 			let tree = self.open_tree(&name)?;
 			if !tree.is_empty()? {
-				return Err(Error(format!("tree {} already contains data", name).into()));
+				return Err(DbError(format!("tree {} already contains data", name).into()).into());
 			}
 
 			let ex_tree = other.open_tree(&name)?;
@@ -186,7 +220,7 @@ impl Db {
 			});
 			let total = match tx_res {
 				Err(TxError::Db(e)) => return Err(e),
-				Err(TxError::Abort(e)) => return Err(e),
+				Err(TxError::Abort(e)) => return Err(e.into()),
 				Ok(x) => x,
 			};
 
@@ -204,24 +238,24 @@ impl Tree {
 	}
 
 	#[inline]
-	pub fn get<T: AsRef<[u8]>>(&self, key: T) -> Result<Option<Value>> {
+	pub fn get<T: AsRef<[u8]>>(&self, key: T) -> DbResult<Option<Value>> {
 		self.0.get(self.1, key.as_ref())
 	}
 	#[inline]
-	pub fn approximate_len(&self) -> Result<usize> {
+	pub fn approximate_len(&self) -> DbResult<usize> {
 		self.0.approximate_len(self.1)
 	}
 	#[inline]
-	pub fn is_empty(&self) -> Result<bool> {
+	pub fn is_empty(&self) -> DbResult<bool> {
 		self.0.is_empty(self.1)
 	}
 
 	#[inline]
-	pub fn first(&self) -> Result<Option<(Value, Value)>> {
+	pub fn first(&self) -> DbResult<Option<(Value, Value)>> {
 		self.iter()?.next().transpose()
 	}
 	#[inline]
-	pub fn get_gt<T: AsRef<[u8]>>(&self, from: T) -> Result<Option<(Value, Value)>> {
+	pub fn get_gt<T: AsRef<[u8]>>(&self, from: T) -> DbResult<Option<(Value, Value)>> {
 		if from.as_ref().is_empty() {
 			self.iter()?.next().transpose()
 		} else {
@@ -233,31 +267,31 @@ impl Tree {
 
 	/// Returns the old value if there was one
 	#[inline]
-	pub fn insert<T: AsRef<[u8]>, U: AsRef<[u8]>>(&self, key: T, value: U) -> Result<()> {
+	pub fn insert<T: AsRef<[u8]>, U: AsRef<[u8]>>(&self, key: T, value: U) -> DbResult<()> {
 		self.0.insert(self.1, key.as_ref(), value.as_ref())
 	}
 	/// Returns the old value if there was one
 	#[inline]
-	pub fn remove<T: AsRef<[u8]>>(&self, key: T) -> Result<()> {
+	pub fn remove<T: AsRef<[u8]>>(&self, key: T) -> DbResult<()> {
 		self.0.remove(self.1, key.as_ref())
 	}
 	/// Clears all values from the tree
 	#[inline]
-	pub fn clear(&self) -> Result<()> {
+	pub fn clear(&self) -> DbResult<()> {
 		self.0.clear(self.1)
 	}
 
 	#[inline]
-	pub fn iter(&self) -> Result<ValueIter<'_>> {
+	pub fn iter(&self) -> DbResult<ValueIter<'_>> {
 		self.0.iter(self.1)
 	}
 	#[inline]
-	pub fn iter_rev(&self) -> Result<ValueIter<'_>> {
+	pub fn iter_rev(&self) -> DbResult<ValueIter<'_>> {
 		self.0.iter_rev(self.1)
 	}
 
 	#[inline]
-	pub fn range<K, R>(&self, range: R) -> Result<ValueIter<'_>>
+	pub fn range<K, R>(&self, range: R) -> DbResult<ValueIter<'_>>
 	where
 		K: AsRef<[u8]>,
 		R: RangeBounds<K>,
@@ -267,7 +301,7 @@ impl Tree {
 		self.0.range(self.1, get_bound(sb), get_bound(eb))
 	}
 	#[inline]
-	pub fn range_rev<K, R>(&self, range: R) -> Result<ValueIter<'_>>
+	pub fn range_rev<K, R>(&self, range: R) -> DbResult<ValueIter<'_>>
 	where
 		K: AsRef<[u8]>,
 		R: RangeBounds<K>,
@@ -282,11 +316,11 @@ impl Tree {
 impl<'a> Transaction<'a> {
 	#[inline]
 	pub fn get<T: AsRef<[u8]>>(&self, tree: &Tree, key: T) -> TxOpResult<Option<Value>> {
-		self.tx.get(tree.1, key.as_ref())
+		self.tx.get(tree.1, key.as_ref()).map_err(Into::into)
 	}
 	#[inline]
 	pub fn len(&self, tree: &Tree) -> TxOpResult<usize> {
-		self.tx.len(tree.1)
+		self.tx.len(tree.1).map_err(Into::into)
 	}
 
 	/// Returns the old value if there was one
@@ -297,26 +331,28 @@ impl<'a> Transaction<'a> {
 		key: T,
 		value: U,
 	) -> TxOpResult<()> {
-		self.tx.insert(tree.1, key.as_ref(), value.as_ref())
+		self.tx
+			.insert(tree.1, key.as_ref(), value.as_ref())
+			.map_err(Into::into)
 	}
 	/// Returns the old value if there was one
 	#[inline]
 	pub fn remove<T: AsRef<[u8]>>(&mut self, tree: &Tree, key: T) -> TxOpResult<()> {
-		self.tx.remove(tree.1, key.as_ref())
+		self.tx.remove(tree.1, key.as_ref()).map_err(Into::into)
 	}
 	/// Clears all values in a tree
 	#[inline]
 	pub fn clear(&mut self, tree: &Tree) -> TxOpResult<()> {
-		self.tx.clear(tree.1)
+		self.tx.clear(tree.1).map_err(Into::into)
 	}
 
 	#[inline]
 	pub fn iter(&self, tree: &Tree) -> TxOpResult<TxValueIter<'_>> {
-		self.tx.iter(tree.1)
+		self.tx.iter(tree.1).map_err(Into::into)
 	}
 	#[inline]
 	pub fn iter_rev(&self, tree: &Tree) -> TxOpResult<TxValueIter<'_>> {
-		self.tx.iter_rev(tree.1)
+		self.tx.iter_rev(tree.1).map_err(Into::into)
 	}
 
 	#[inline]
@@ -327,7 +363,9 @@ impl<'a> Transaction<'a> {
 	{
 		let sb = range.start_bound();
 		let eb = range.end_bound();
-		self.tx.range(tree.1, get_bound(sb), get_bound(eb))
+		self.tx
+			.range(tree.1, get_bound(sb), get_bound(eb))
+			.map_err(Into::into)
 	}
 	#[inline]
 	pub fn range_rev<K, R>(&self, tree: &Tree, range: R) -> TxOpResult<TxValueIter<'_>>
@@ -337,7 +375,9 @@ impl<'a> Transaction<'a> {
 	{
 		let sb = range.start_bound();
 		let eb = range.end_bound();
-		self.tx.range_rev(tree.1, get_bound(sb), get_bound(eb))
+		self.tx
+			.range_rev(tree.1, get_bound(sb), get_bound(eb))
+			.map_err(Into::into)
 	}
 
 	#[inline]
@@ -350,60 +390,60 @@ impl<'a> Transaction<'a> {
 
 pub(crate) trait IDb: Send + Sync {
 	fn engine(&self) -> String;
-	fn open_tree(&self, name: &str) -> Result<usize>;
+	fn open_tree(&self, name: &str) -> DbResult<usize>;
-	fn list_trees(&self) -> Result<Vec<String>>;
+	fn list_trees(&self) -> DbResult<Vec<String>>;
-	fn snapshot(&self, path: &Path) -> Result<()>;
+	fn snapshot(&self, path: &Path) -> DbResult<()>;
 
-	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value>>;
+	fn get(&self, tree: usize, key: &[u8]) -> DbResult<Option<Value>>;
-	fn approximate_len(&self, tree: usize) -> Result<usize>;
+	fn approximate_len(&self, tree: usize) -> DbResult<usize>;
-	fn is_empty(&self, tree: usize) -> Result<bool>;
+	fn is_empty(&self, tree: usize) -> DbResult<bool>;
 
-	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<()>;
+	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> DbResult<()>;
-	fn remove(&self, tree: usize, key: &[u8]) -> Result<()>;
+	fn remove(&self, tree: usize, key: &[u8]) -> DbResult<()>;
-	fn clear(&self, tree: usize) -> Result<()>;
+	fn clear(&self, tree: usize) -> DbResult<()>;
 
-	fn iter(&self, tree: usize) -> Result<ValueIter<'_>>;
+	fn iter(&self, tree: usize) -> DbResult<ValueIter<'_>>;
-	fn iter_rev(&self, tree: usize) -> Result<ValueIter<'_>>;
+	fn iter_rev(&self, tree: usize) -> DbResult<ValueIter<'_>>;
 
 	fn range<'r>(
 		&self,
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'_>>;
+	) -> DbResult<ValueIter<'_>>;
 	fn range_rev<'r>(
 		&self,
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'_>>;
+	) -> DbResult<ValueIter<'_>>;
 
 	fn transaction(&self, f: &dyn ITxFn) -> TxResult<OnCommit, ()>;
 }
 
 pub(crate) trait ITx {
-	fn get(&self, tree: usize, key: &[u8]) -> TxOpResult<Option<Value>>;
+	fn get(&self, tree: usize, key: &[u8]) -> DbResult<Option<Value>>;
-	fn len(&self, tree: usize) -> TxOpResult<usize>;
+	fn len(&self, tree: usize) -> DbResult<usize>;
 
-	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> TxOpResult<()>;
+	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> DbResult<()>;
-	fn remove(&mut self, tree: usize, key: &[u8]) -> TxOpResult<()>;
+	fn remove(&mut self, tree: usize, key: &[u8]) -> DbResult<()>;
-	fn clear(&mut self, tree: usize) -> TxOpResult<()>;
+	fn clear(&mut self, tree: usize) -> DbResult<()>;
 
-	fn iter(&self, tree: usize) -> TxOpResult<TxValueIter<'_>>;
+	fn iter(&self, tree: usize) -> DbResult<TxValueIter<'_>>;
-	fn iter_rev(&self, tree: usize) -> TxOpResult<TxValueIter<'_>>;
+	fn iter_rev(&self, tree: usize) -> DbResult<TxValueIter<'_>>;
 
 	fn range<'r>(
 		&self,
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> TxOpResult<TxValueIter<'_>>;
+	) -> DbResult<TxValueIter<'_>>;
 	fn range_rev<'r>(
 		&self,
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> TxOpResult<TxValueIter<'_>>;
+	) -> DbResult<TxValueIter<'_>>;
 }
 
 pub(crate) trait ITxFn {

src/db/lmdb_adapter.rs

@@ -14,7 +14,7 @@ type Database = heed::Database<Bytes, Bytes>;
 
 use crate::{
 	open::{Engine, OpenOpt},
-	Db, Error, IDb, ITx, ITxFn, OnCommit, Result, TxError, TxFnResult, TxOpError, TxOpResult,
+	Db, DbError, DbResult, Error, IDb, ITx, ITxFn, OnCommit, TxError, TxFnResult, TxOpError,
 	TxResult, TxValueIter, Value, ValueIter,
 };
 
@@ -22,10 +22,10 @@ pub use heed;
 
 // ---- top-level open function
 
-pub(crate) fn open_db(path: &PathBuf, opt: &OpenOpt) -> Result<Db> {
+pub(crate) fn open_db(path: &PathBuf, opt: &OpenOpt) -> DbResult<Db> {
 	info!("Opening LMDB database at: {}", path.display());
 	if let Err(e) = std::fs::create_dir_all(path) {
-		return Err(Error(
+		return Err(DbError(
 			format!("Unable to create LMDB data directory: {}", e).into(),
 		));
 	}
@@ -48,7 +48,7 @@ pub(crate) fn open_db(path: &PathBuf, opt: &OpenOpt) -> Result<Db> {
 		env_builder.open(path)
 	};
 	match open_res {
-		Err(heed::Error::Io(e)) if e.kind() == std::io::ErrorKind::OutOfMemory => Err(Error(
+		Err(heed::Error::Io(e)) if e.kind() == std::io::ErrorKind::OutOfMemory => Err(DbError(
 			"OutOfMemory error while trying to open LMDB database. This can happen \
                 if your operating system is not allowing you to use sufficient virtual \
                 memory address space. Please check that no limit is set (ulimit -v). \
@@ -56,22 +56,28 @@ pub(crate) fn open_db(path: &PathBuf, opt: &OpenOpt) -> Result<Db> {
                 On 32-bit machines, you should probably switch to another database engine."
 				.into(),
 		)),
-		Err(e) => Err(Error(format!("Cannot open LMDB database: {}", e).into())),
+		Err(e) => Err(DbError(format!("Cannot open LMDB database: {}", e).into())),
 		Ok(db) => Ok(LmdbDb::init(db)),
 	}
 }
 
 // -- err
 
+impl From<heed::Error> for DbError {
+	fn from(e: heed::Error) -> DbError {
+		DbError(format!("LMDB: {}", e).into())
+	}
+}
+
 impl From<heed::Error> for Error {
 	fn from(e: heed::Error) -> Error {
-		Error(format!("LMDB: {}", e).into())
+		DbError::from(e).into()
 	}
 }
 
 impl From<heed::Error> for TxOpError {
 	fn from(e: heed::Error) -> TxOpError {
-		TxOpError(e.into())
+		DbError::from(e).into()
 	}
 }
 
@@ -91,14 +97,14 @@ impl LmdbDb {
 		Db(Arc::new(s))
 	}
 
-	fn get_tree(&self, i: usize) -> Result<Database> {
+	fn get_tree(&self, i: usize) -> DbResult<Database> {
 		self.trees
 			.read()
 			.unwrap()
 			.0
 			.get(i)
 			.cloned()
-			.ok_or_else(|| Error("invalid tree id".into()))
+			.ok_or_else(|| DbError("invalid tree id".into()))
 	}
 }
 
@@ -107,7 +113,7 @@ impl IDb for LmdbDb {
 		"LMDB (using Heed crate)".into()
 	}
 
-	fn open_tree(&self, name: &str) -> Result<usize> {
+	fn open_tree(&self, name: &str) -> DbResult<usize> {
 		let mut trees = self.trees.write().unwrap();
 		if let Some(i) = trees.1.get(name) {
 			Ok(*i)
@@ -122,7 +128,7 @@ impl IDb for LmdbDb {
 		}
 	}
 
-	fn list_trees(&self) -> Result<Vec<String>> {
+	fn list_trees(&self) -> DbResult<Vec<String>> {
 		let rtxn = self.db.read_txn()?;
 		let tree0 = match self
 			.db
@@ -153,7 +159,7 @@ impl IDb for LmdbDb {
 		Ok(ret2)
 	}
 
-	fn snapshot(&self, base_path: &Path) -> Result<()> {
+	fn snapshot(&self, base_path: &Path) -> DbResult<()> {
 		std::fs::create_dir_all(base_path)?;
 		let path = Engine::Lmdb.db_path(base_path);
 		self.db
@@ -163,7 +169,7 @@ impl IDb for LmdbDb {
 
 	// ----
 
-	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value>> {
+	fn get(&self, tree: usize, key: &[u8]) -> DbResult<Option<Value>> {
 		let tree = self.get_tree(tree)?;
 
 		let tx = self.db.read_txn()?;
@@ -174,18 +180,18 @@ impl IDb for LmdbDb {
 		}
 	}
 
-	fn approximate_len(&self, tree: usize) -> Result<usize> {
+	fn approximate_len(&self, tree: usize) -> DbResult<usize> {
 		let tree = self.get_tree(tree)?;
 		let tx = self.db.read_txn()?;
 		Ok(tree.len(&tx)?.try_into().unwrap())
 	}
-	fn is_empty(&self, tree: usize) -> Result<bool> {
+	fn is_empty(&self, tree: usize) -> DbResult<bool> {
 		let tree = self.get_tree(tree)?;
 		let tx = self.db.read_txn()?;
 		Ok(tree.is_empty(&tx)?)
 	}
 
-	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
+	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> DbResult<()> {
 		let tree = self.get_tree(tree)?;
 		let mut tx = self.db.write_txn()?;
 		tree.put(&mut tx, key, value)?;
@@ -193,7 +199,7 @@ impl IDb for LmdbDb {
 		Ok(())
 	}
 
-	fn remove(&self, tree: usize, key: &[u8]) -> Result<()> {
+	fn remove(&self, tree: usize, key: &[u8]) -> DbResult<()> {
 		let tree = self.get_tree(tree)?;
 		let mut tx = self.db.write_txn()?;
 		tree.delete(&mut tx, key)?;
@@ -201,7 +207,7 @@ impl IDb for LmdbDb {
 		Ok(())
 	}
 
-	fn clear(&self, tree: usize) -> Result<()> {
+	fn clear(&self, tree: usize) -> DbResult<()> {
 		let tree = self.get_tree(tree)?;
 		let mut tx = self.db.write_txn()?;
 		tree.clear(&mut tx)?;
@@ -209,14 +215,14 @@ impl IDb for LmdbDb {
 		Ok(())
 	}
 
-	fn iter(&self, tree: usize) -> Result<ValueIter<'_>> {
+	fn iter(&self, tree: usize) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 		let tx = self.db.read_txn()?;
 		// Safety: the cloture does not store its argument anywhere,
 		unsafe { TxAndIterator::make(tx, |tx| Ok(tree.iter(tx)?)) }
 	}
 
-	fn iter_rev(&self, tree: usize) -> Result<ValueIter<'_>> {
+	fn iter_rev(&self, tree: usize) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 		let tx = self.db.read_txn()?;
 		// Safety: the cloture does not store its argument anywhere,
@@ -228,7 +234,7 @@ impl IDb for LmdbDb {
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'_>> {
+	) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 		let tx = self.db.read_txn()?;
 		// Safety: the cloture does not store its argument anywhere,
@@ -239,7 +245,7 @@ impl IDb for LmdbDb {
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'_>> {
+	) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 		let tx = self.db.read_txn()?;
 		// Safety: the cloture does not store its argument anywhere,
@@ -271,9 +277,9 @@ impl IDb for LmdbDb {
 			}
 			TxFnResult::DbErr => {
 				tx.tx.abort();
-				Err(TxError::Db(Error(
+				Err(TxError::Db(
-					"(this message will be discarded)".into(),
+					DbError("(this message will be discarded)".into()).into(),
-				)))
+				))
 			}
 		}
 	}
@@ -287,49 +293,49 @@ struct LmdbTx<'a> {
 }
 
 impl<'a> LmdbTx<'a> {
-	fn get_tree(&self, i: usize) -> TxOpResult<&Database> {
+	fn get_tree(&self, i: usize) -> DbResult<&Database> {
 		self.trees.get(i).ok_or_else(|| {
-			TxOpError(Error(
+			DbError(
 				"invalid tree id (it might have been opened after the transaction started)".into(),
-			))
+			)
 		})
 	}
 }
 
 impl<'a> ITx for LmdbTx<'a> {
-	fn get(&self, tree: usize, key: &[u8]) -> TxOpResult<Option<Value>> {
+	fn get(&self, tree: usize, key: &[u8]) -> DbResult<Option<Value>> {
 		let tree = self.get_tree(tree)?;
 		match tree.get(&self.tx, key)? {
 			Some(v) => Ok(Some(v.to_vec())),
 			None => Ok(None),
 		}
 	}
-	fn len(&self, tree: usize) -> TxOpResult<usize> {
+	fn len(&self, tree: usize) -> DbResult<usize> {
 		let tree = self.get_tree(tree)?;
 		Ok(tree.len(&self.tx)? as usize)
 	}
 
-	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> TxOpResult<()> {
+	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> DbResult<()> {
 		let tree = *self.get_tree(tree)?;
 		tree.put(&mut self.tx, key, value)?;
 		Ok(())
 	}
-	fn remove(&mut self, tree: usize, key: &[u8]) -> TxOpResult<()> {
+	fn remove(&mut self, tree: usize, key: &[u8]) -> DbResult<()> {
 		let tree = *self.get_tree(tree)?;
 		tree.delete(&mut self.tx, key)?;
 		Ok(())
 	}
-	fn clear(&mut self, tree: usize) -> TxOpResult<()> {
+	fn clear(&mut self, tree: usize) -> DbResult<()> {
 		let tree = *self.get_tree(tree)?;
 		tree.clear(&mut self.tx)?;
 		Ok(())
 	}
 
-	fn iter(&self, tree: usize) -> TxOpResult<TxValueIter<'_>> {
+	fn iter(&self, tree: usize) -> DbResult<TxValueIter<'_>> {
 		let tree = *self.get_tree(tree)?;
 		Ok(Box::new(tree.iter(&self.tx)?.map(tx_iter_item)))
 	}
-	fn iter_rev(&self, tree: usize) -> TxOpResult<TxValueIter<'_>> {
+	fn iter_rev(&self, tree: usize) -> DbResult<TxValueIter<'_>> {
 		let tree = *self.get_tree(tree)?;
 		Ok(Box::new(tree.rev_iter(&self.tx)?.map(tx_iter_item)))
 	}
@@ -339,7 +345,7 @@ impl<'a> ITx for LmdbTx<'a> {
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> TxOpResult<TxValueIter<'_>> {
+	) -> DbResult<TxValueIter<'_>> {
 		let tree = *self.get_tree(tree)?;
 		Ok(Box::new(
 			tree.range(&self.tx, &(low, high))?.map(tx_iter_item),
@@ -350,7 +356,7 @@ impl<'a> ITx for LmdbTx<'a> {
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> TxOpResult<TxValueIter<'_>> {
+	) -> DbResult<TxValueIter<'_>> {
 		let tree = *self.get_tree(tree)?;
 		Ok(Box::new(
 			tree.rev_range(&self.tx, &(low, high))?.map(tx_iter_item),
@@ -386,9 +392,9 @@ where
 	}
 
 	/// Safety: iterfun must not store its argument anywhere but in its result.
-	unsafe fn make<F>(tx: RoTxn<'a, WithTls>, iterfun: F) -> Result<ValueIter<'a>>
+	unsafe fn make<F>(tx: RoTxn<'a, WithTls>, iterfun: F) -> DbResult<ValueIter<'a>>
 	where
-		F: FnOnce(&'a RoTxn<'a>) -> Result<I>,
+		F: FnOnce(&'a RoTxn<'a>) -> DbResult<I>,
 	{
 		let res = TxAndIterator {
 			tx,
@@ -436,13 +442,13 @@ impl<'a, I> Iterator for TxAndIteratorPin<'a, I>
 where
 	I: Iterator<Item = IteratorItem<'a>> + 'a,
 {
-	type Item = Result<(Value, Value)>;
+	type Item = DbResult<(Value, Value)>;
 
 	fn next(&mut self) -> Option<Self::Item> {
 		let mut_ref = Pin::as_mut(&mut self.0);
 		let next = mut_ref.iter().as_mut()?.next()?;
 		let res = match next {
-			Err(e) => Err(e.into()),
+			Err(e) => Err(DbError::from(e)),
 			Ok((k, v)) => Ok((k.to_vec(), v.to_vec())),
 		};
 		Some(res)
@@ -453,9 +459,9 @@ where
 
 fn tx_iter_item<'a>(
 	item: std::result::Result<(&'a [u8], &'a [u8]), heed::Error>,
-) -> TxOpResult<(Vec<u8>, Vec<u8>)> {
+) -> DbResult<(Vec<u8>, Vec<u8>)> {
 	item.map(|(k, v)| (k.to_vec(), v.to_vec()))
-		.map_err(|e| TxOpError(Error::from(e)))
+		.map_err(DbError::from)
 }
 
 // ---- utility ----

src/db/open.rs

@@ -1,6 +1,6 @@
 use std::path::{Path, PathBuf};
 
-use crate::{Db, Error, Result};
+use crate::{Db, DbError, Error, Result};
 
 /// List of supported database engine types
 ///
@@ -49,14 +49,14 @@ impl std::str::FromStr for Engine {
 			"lmdb" | "heed" => Ok(Self::Lmdb),
 			"sqlite" | "sqlite3" | "rusqlite" => Ok(Self::Sqlite),
             "fjall" => Ok(Self::Fjall),
-			"sled" => Err(Error("Sled is no longer supported as a database engine. Converting your old metadata db can be done using an older Garage binary (e.g. v0.9.4).".into())),
+			"sled" => Err(DbError("Sled is no longer supported as a database engine. Converting your old metadata db can be done using an older Garage binary (e.g. v0.9.4).".into()).into()),
-			kind => Err(Error(
+			kind => Err(DbError(
 				format!(
 					"Invalid DB engine: {} (options are: lmdb, sqlite, fjall)",
 					kind
 				)
 				.into(),
-			)),
+			).into()),
 		}
 	}
 }
@@ -72,22 +72,23 @@ pub fn open_db(path: &PathBuf, engine: Engine, opt: &OpenOpt) -> Result<Db> {
 	match engine {
 		// ---- Sqlite DB ----
 		#[cfg(feature = "sqlite")]
-		Engine::Sqlite => crate::sqlite_adapter::open_db(path, opt),
+		Engine::Sqlite => Ok(crate::sqlite_adapter::open_db(path, opt)?),
 
 		// ---- LMDB DB ----
 		#[cfg(feature = "lmdb")]
-		Engine::Lmdb => crate::lmdb_adapter::open_db(path, opt),
+		Engine::Lmdb => Ok(crate::lmdb_adapter::open_db(path, opt)?),
 
 		// ---- Fjall DB ----
 		#[cfg(feature = "fjall")]
-		Engine::Fjall => crate::fjall_adapter::open_db(path, opt),
+		Engine::Fjall => Ok(crate::fjall_adapter::open_db(path, opt)?),
 
 		// Pattern is unreachable when all supported DB engines are compiled into binary. The allow
 		// attribute is added so that we won't have to change this match in case stop building
 		// support for one or more engines by default.
 		#[allow(unreachable_patterns)]
-		engine => Err(Error(
+		engine => Err(DbError(
 			format!("DB engine support not available in this build: {}", engine).into(),
-		)),
+		)
+		.into()),
 	}
 }

src/db/sqlite_adapter.rs

@@ -12,7 +12,7 @@ use rusqlite::{params, Rows, Statement, Transaction};
 
 use crate::{
 	open::{Engine, OpenOpt},
-	Db, Error, IDb, ITx, ITxFn, OnCommit, Result, TxError, TxFnResult, TxOpError, TxOpResult,
+	Db, DbError, DbResult, Error, IDb, ITx, ITxFn, OnCommit, TxError, TxFnResult, TxOpError,
 	TxResult, TxValueIter, Value, ValueIter,
 };
 
@@ -20,7 +20,7 @@ pub use rusqlite;
 
 // ---- top-level open function
 
-pub(crate) fn open_db(path: &PathBuf, opt: &OpenOpt) -> Result<Db> {
+pub(crate) fn open_db(path: &PathBuf, opt: &OpenOpt) -> DbResult<Db> {
 	info!("Opening Sqlite database at: {}", path.display());
 	let manager = r2d2_sqlite::SqliteConnectionManager::file(path);
 	SqliteDb::open(manager, opt.fsync)
@@ -32,21 +32,33 @@ type Connection = r2d2::PooledConnection<SqliteConnectionManager>;
 
 // --- err
 
+impl From<rusqlite::Error> for DbError {
+	fn from(e: rusqlite::Error) -> DbError {
+		DbError(format!("Sqlite: {}", e).into())
+	}
+}
+
 impl From<rusqlite::Error> for Error {
 	fn from(e: rusqlite::Error) -> Error {
-		Error(format!("Sqlite: {}", e).into())
+		DbError::from(e).into()
+	}
+}
+
+impl From<r2d2::Error> for DbError {
+	fn from(e: r2d2::Error) -> DbError {
+		DbError(format!("Sqlite: {}", e).into())
 	}
 }
 
 impl From<r2d2::Error> for Error {
 	fn from(e: r2d2::Error) -> Error {
-		Error(format!("Sqlite: {}", e).into())
+		DbError::from(e).into()
 	}
 }
 
 impl From<rusqlite::Error> for TxOpError {
 	fn from(e: rusqlite::Error) -> TxOpError {
-		TxOpError(e.into())
+		DbError::from(e).into()
 	}
 }
 
@@ -62,7 +74,7 @@ pub struct SqliteDb {
 }
 
 impl SqliteDb {
-	pub fn open(manager: SqliteConnectionManager, sync_mode: bool) -> Result<Db> {
+	pub fn open(manager: SqliteConnectionManager, sync_mode: bool) -> DbResult<Db> {
 		let manager = manager.with_init(move |db| {
 			db.pragma_update(None, "journal_mode", "WAL")?;
 			if sync_mode {
@@ -82,16 +94,16 @@ impl SqliteDb {
 }
 
 impl SqliteDb {
-	fn get_tree(&self, i: usize) -> Result<Arc<str>> {
+	fn get_tree(&self, i: usize) -> DbResult<Arc<str>> {
 		self.trees
 			.read()
 			.unwrap()
 			.get(i)
 			.cloned()
-			.ok_or_else(|| Error("invalid tree id".into()))
+			.ok_or_else(|| DbError("invalid tree id".into()))
 	}
 
-	fn internal_get(&self, db: &Connection, tree: &str, key: &[u8]) -> Result<Option<Value>> {
+	fn internal_get(&self, db: &Connection, tree: &str, key: &[u8]) -> DbResult<Option<Value>> {
 		let mut stmt = db.prepare(&format!("SELECT v FROM {} WHERE k = ?1", tree))?;
 		let mut res_iter = stmt.query([key])?;
 		match res_iter.next()? {
@@ -106,7 +118,7 @@ impl IDb for SqliteDb {
 		format!("sqlite3 v{} (using rusqlite crate)", rusqlite::version())
 	}
 
-	fn open_tree(&self, name: &str) -> Result<usize> {
+	fn open_tree(&self, name: &str) -> DbResult<usize> {
 		let name = format!("tree_{}", name.replace(':', "_COLON_"));
 		let mut trees = self.trees.write().unwrap();
 
@@ -133,7 +145,7 @@ impl IDb for SqliteDb {
 		}
 	}
 
-	fn list_trees(&self) -> Result<Vec<String>> {
+	fn list_trees(&self) -> DbResult<Vec<String>> {
 		let mut trees = vec![];
 
 		let db = self.db.get()?;
@@ -150,13 +162,13 @@ impl IDb for SqliteDb {
 		Ok(trees)
 	}
 
-	fn snapshot(&self, base_path: &Path) -> Result<()> {
+	fn snapshot(&self, base_path: &Path) -> DbResult<()> {
 		std::fs::create_dir_all(base_path)?;
 		let path = Engine::Sqlite
 			.db_path(base_path)
 			.into_os_string()
 			.into_string()
-			.map_err(|_| Error("invalid sqlite path string".into()))?;
+			.map_err(|_| DbError("invalid sqlite path string".into()))?;
 
 		info!("Start sqlite VACUUM INTO `{}`", path);
 		self.db.get()?.execute("VACUUM INTO ?1", params![path])?;
@@ -167,12 +179,12 @@ impl IDb for SqliteDb {
 
 	// ----
 
-	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value>> {
+	fn get(&self, tree: usize, key: &[u8]) -> DbResult<Option<Value>> {
 		let tree = self.get_tree(tree)?;
 		self.internal_get(&self.db.get()?, &tree, key)
 	}
 
-	fn approximate_len(&self, tree: usize) -> Result<usize> {
+	fn approximate_len(&self, tree: usize) -> DbResult<usize> {
 		let tree = self.get_tree(tree)?;
 		let db = self.db.get()?;
 
@@ -184,11 +196,11 @@ impl IDb for SqliteDb {
 		}
 	}
 
-	fn is_empty(&self, tree: usize) -> Result<bool> {
+	fn is_empty(&self, tree: usize) -> DbResult<bool> {
 		Ok(self.approximate_len(tree)? == 0)
 	}
 
-	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
+	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> DbResult<()> {
 		let tree = self.get_tree(tree)?;
 		let db = self.db.get()?;
 		let lock = self.write_lock.lock();
@@ -206,7 +218,7 @@ impl IDb for SqliteDb {
 		Ok(())
 	}
 
-	fn remove(&self, tree: usize, key: &[u8]) -> Result<()> {
+	fn remove(&self, tree: usize, key: &[u8]) -> DbResult<()> {
 		let tree = self.get_tree(tree)?;
 		let db = self.db.get()?;
 		let lock = self.write_lock.lock();
@@ -217,7 +229,7 @@ impl IDb for SqliteDb {
 		Ok(())
 	}
 
-	fn clear(&self, tree: usize) -> Result<()> {
+	fn clear(&self, tree: usize) -> DbResult<()> {
 		let tree = self.get_tree(tree)?;
 		let db = self.db.get()?;
 		let lock = self.write_lock.lock();
@@ -228,13 +240,13 @@ impl IDb for SqliteDb {
 		Ok(())
 	}
 
-	fn iter(&self, tree: usize) -> Result<ValueIter<'_>> {
+	fn iter(&self, tree: usize) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 		let sql = format!("SELECT k, v FROM {} ORDER BY k ASC", tree);
 		DbValueIterator::make(self.db.get()?, &sql, [])
 	}
 
-	fn iter_rev(&self, tree: usize) -> Result<ValueIter<'_>> {
+	fn iter_rev(&self, tree: usize) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 		let sql = format!("SELECT k, v FROM {} ORDER BY k DESC", tree);
 		DbValueIterator::make(self.db.get()?, &sql, [])
@@ -245,7 +257,7 @@ impl IDb for SqliteDb {
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'_>> {
+	) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 
 		let (bounds_sql, params) = bounds_sql(low, high);
@@ -263,7 +275,7 @@ impl IDb for SqliteDb {
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'_>> {
+	) -> DbResult<ValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 
 		let (bounds_sql, params) = bounds_sql(low, high);
@@ -300,9 +312,9 @@ impl IDb for SqliteDb {
 			}
 			TxFnResult::DbErr => {
 				tx.tx.rollback().map_err(Error::from).map_err(TxError::Db)?;
-				Err(TxError::Db(Error(
+				Err(TxError::Db(
-					"(this message will be discarded)".into(),
+					DbError("(this message will be discarded)".into()).into(),
-				)))
+				))
 			}
 		};
 
@@ -320,15 +332,15 @@ struct SqliteTx<'a> {
 }
 
 impl<'a> SqliteTx<'a> {
-	fn get_tree(&self, i: usize) -> TxOpResult<&'_ str> {
+	fn get_tree(&self, i: usize) -> DbResult<&'_ str> {
 		self.trees.get(i).map(Arc::as_ref).ok_or_else(|| {
-			TxOpError(Error(
+			DbError(
 				"invalid tree id (it might have been opened after the transaction started)".into(),
-			))
+			)
 		})
 	}
 
-	fn internal_get(&self, tree: &str, key: &[u8]) -> TxOpResult<Option<Value>> {
+	fn internal_get(&self, tree: &str, key: &[u8]) -> DbResult<Option<Value>> {
 		let mut stmt = self
 			.tx
 			.prepare(&format!("SELECT v FROM {} WHERE k = ?1", tree))?;
@@ -341,11 +353,11 @@ impl<'a> SqliteTx<'a> {
 }
 
 impl<'a> ITx for SqliteTx<'a> {
-	fn get(&self, tree: usize, key: &[u8]) -> TxOpResult<Option<Value>> {
+	fn get(&self, tree: usize, key: &[u8]) -> DbResult<Option<Value>> {
 		let tree = self.get_tree(tree)?;
 		self.internal_get(tree, key)
 	}
-	fn len(&self, tree: usize) -> TxOpResult<usize> {
+	fn len(&self, tree: usize) -> DbResult<usize> {
 		let tree = self.get_tree(tree)?;
 		let mut stmt = self.tx.prepare(&format!("SELECT COUNT(*) FROM {}", tree))?;
 		let mut res_iter = stmt.query([])?;
@@ -355,30 +367,30 @@ impl<'a> ITx for SqliteTx<'a> {
 		}
 	}
 
-	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> TxOpResult<()> {
+	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> DbResult<()> {
 		let tree = self.get_tree(tree)?;
 		let sql = format!("INSERT OR REPLACE INTO {} (k, v) VALUES (?1, ?2)", tree);
 		self.tx.execute(&sql, params![key, value])?;
 		Ok(())
 	}
-	fn remove(&mut self, tree: usize, key: &[u8]) -> TxOpResult<()> {
+	fn remove(&mut self, tree: usize, key: &[u8]) -> DbResult<()> {
 		let tree = self.get_tree(tree)?;
 		self.tx
 			.execute(&format!("DELETE FROM {} WHERE k = ?1", tree), params![key])?;
 		Ok(())
 	}
-	fn clear(&mut self, tree: usize) -> TxOpResult<()> {
+	fn clear(&mut self, tree: usize) -> DbResult<()> {
 		let tree = self.get_tree(tree)?;
 		self.tx.execute(&format!("DELETE FROM {}", tree), [])?;
 		Ok(())
 	}
 
-	fn iter(&self, tree: usize) -> TxOpResult<TxValueIter<'_>> {
+	fn iter(&self, tree: usize) -> DbResult<TxValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 		let sql = format!("SELECT k, v FROM {} ORDER BY k ASC", tree);
 		TxValueIterator::make(self, &sql, [])
 	}
-	fn iter_rev(&self, tree: usize) -> TxOpResult<TxValueIter<'_>> {
+	fn iter_rev(&self, tree: usize) -> DbResult<TxValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 		let sql = format!("SELECT k, v FROM {} ORDER BY k DESC", tree);
 		TxValueIterator::make(self, &sql, [])
@@ -389,7 +401,7 @@ impl<'a> ITx for SqliteTx<'a> {
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> TxOpResult<TxValueIter<'_>> {
+	) -> DbResult<TxValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 
 		let (bounds_sql, params) = bounds_sql(low, high);
@@ -407,7 +419,7 @@ impl<'a> ITx for SqliteTx<'a> {
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> TxOpResult<TxValueIter<'_>> {
+	) -> DbResult<TxValueIter<'_>> {
 		let tree = self.get_tree(tree)?;
 
 		let (bounds_sql, params) = bounds_sql(low, high);
@@ -439,7 +451,7 @@ impl DbValueIterator {
 		db: Connection,
 		sql: &str,
 		args: P,
-	) -> Result<ValueIter<'res>> {
+	) -> DbResult<ValueIter<'res>> {
 		let res = DbValueIterator {
 			db,
 			stmt: None,
@@ -484,7 +496,7 @@ impl Drop for DbValueIterator {
 struct DbValueIteratorPin(Pin<Box<DbValueIterator>>);
 
 impl Iterator for DbValueIteratorPin {
-	type Item = Result<(Value, Value)>;
+	type Item = DbResult<(Value, Value)>;
 
 	fn next(&mut self) -> Option<Self::Item> {
 		let mut_ref = Pin::as_mut(&mut self.0);
@@ -509,7 +521,7 @@ impl<'a> TxValueIterator<'a> {
 		tx: &'a SqliteTx<'a>,
 		sql: &str,
 		args: P,
-	) -> TxOpResult<TxValueIter<'a>> {
+	) -> DbResult<TxValueIter<'a>> {
 		let stmt = tx.tx.prepare(sql)?;
 		let res = TxValueIterator {
 			stmt,
@@ -543,7 +555,7 @@ impl<'a> Drop for TxValueIterator<'a> {
 struct TxValueIteratorPin<'a>(Pin<Box<TxValueIterator<'a>>>);
 
 impl<'a> Iterator for TxValueIteratorPin<'a> {
-	type Item = TxOpResult<(Value, Value)>;
+	type Item = DbResult<(Value, Value)>;
 
 	fn next(&mut self) -> Option<Self::Item> {
 		let mut_ref = Pin::as_mut(&mut self.0);

src/db/typed.rs

@@ -0,0 +1,241 @@
+use std::marker::PhantomData;
+use std::ops::{Bound, RangeBounds};
+
+// Todo: some parts of this code, notably around ranges are never used but are here to prepare
+// the migration of the parts of the codebase that still use untyped trees. At one point, this
+// migration should be done or these functions deleted.
+
+use super::{
+	DbResult, DecodeError, Error, Result, Transaction, Tree, TxOpError, TxOpResult, TxValueIter,
+	ValueIter,
+};
+
+pub use super::Db;
+
+pub trait DbBytes: Sized {
+	fn encode(&self) -> Vec<u8>;
+	fn decode(bytes: &[u8]) -> std::result::Result<Self, DecodeError>;
+}
+
+/// Subtrait of [`DbBytes`] for types used as tree keys with operations where order matters
+/// (`get_gt`, range, etc...).
+///
+/// Implementors must guarantee that the byte encoding is order-preserving:
+/// for any `a, b: Self`, `a.cmp(&b) == a.encode().cmp(&b.encode())`.
+pub trait DbOrdKey: DbBytes + Ord {}
+
+#[derive(Clone)]
+pub struct TypedTree<K, V> {
+	inner: Tree,
+	_phantom: PhantomData<[(K, V)]>,
+}
+
+impl<K: DbBytes, V: DbBytes> TypedTree<K, V> {
+	pub fn new(tree: Tree) -> Self {
+		Self {
+			inner: tree,
+			_phantom: PhantomData,
+		}
+	}
+
+	pub fn db(&self) -> Db {
+		self.inner.db()
+	}
+
+	pub fn untyped(&self) -> &Tree {
+		&self.inner
+	}
+
+	pub fn get(&self, key: &K) -> Result<Option<V>> {
+		self.inner
+			.get(key.encode())?
+			.map(|v| V::decode(&v).map_err(Error::from))
+			.transpose()
+	}
+
+	pub fn approximate_len(&self) -> DbResult<usize> {
+		self.inner.approximate_len()
+	}
+
+	pub fn is_empty(&self) -> DbResult<bool> {
+		self.inner.is_empty()
+	}
+
+	pub fn insert(&self, key: &K, value: &V) -> DbResult<()> {
+		self.inner.insert(key.encode(), value.encode())
+	}
+
+	pub fn remove(&self, key: &K) -> DbResult<()> {
+		self.inner.remove(key.encode())
+	}
+
+	pub fn clear(&self) -> DbResult<()> {
+		self.inner.clear()
+	}
+
+	pub fn tx_get(&self, tx: &Transaction<'_>, key: &K) -> TxOpResult<Option<V>> {
+		tx.get(&self.inner, key.encode())?
+			.map(|v| V::decode(&v).map_err(TxOpError::from))
+			.transpose()
+	}
+
+	pub fn tx_insert(&self, tx: &mut Transaction<'_>, key: &K, value: &V) -> TxOpResult<()> {
+		tx.insert(&self.inner, key.encode(), value.encode())
+	}
+
+	pub fn tx_remove(&self, tx: &mut Transaction<'_>, key: &K) -> TxOpResult<()> {
+		tx.remove(&self.inner, key.encode())
+	}
+
+	pub fn tx_clear(&self, tx: &mut Transaction<'_>) -> TxOpResult<()> {
+		tx.clear(&self.inner)
+	}
+}
+
+impl<K: DbOrdKey, V: DbBytes> TypedTree<K, V> {
+	pub fn first(&self) -> Result<Option<(K, V)>> {
+		self.iter()?.next().transpose()
+	}
+
+	pub fn get_gt(&self, from: &K) -> Result<Option<(K, V)>> {
+		self.inner
+			.get_gt(from.encode())?
+			.map(|(k, v)| {
+				Ok((
+					K::decode(&k).map_err(Error::from)?,
+					V::decode(&v).map_err(Error::from)?,
+				))
+			})
+			.transpose()
+	}
+
+	pub fn iter(&self) -> Result<TypedIter<'_, K, V>> {
+		Ok(TypedIter::new(self.inner.iter()?))
+	}
+
+	pub fn iter_rev(&self) -> Result<TypedIter<'_, K, V>> {
+		Ok(TypedIter::new(self.inner.iter_rev()?))
+	}
+
+	pub fn range<R: RangeBounds<K>>(&self, range: R) -> Result<TypedIter<'_, K, V>> {
+		Ok(TypedIter::new(self.inner.range(encode_range(range))?))
+	}
+
+	pub fn range_rev<R: RangeBounds<K>>(&self, range: R) -> Result<TypedIter<'_, K, V>> {
+		Ok(TypedIter::new(self.inner.range_rev(encode_range(range))?))
+	}
+
+	pub fn tx_iter<'t>(&self, tx: &'t Transaction<'_>) -> TxOpResult<TypedTxIter<'t, K, V>> {
+		Ok(TypedTxIter::new(tx.iter(&self.inner)?))
+	}
+
+	pub fn tx_iter_rev<'t>(&self, tx: &'t Transaction<'_>) -> TxOpResult<TypedTxIter<'t, K, V>> {
+		Ok(TypedTxIter::new(tx.iter_rev(&self.inner)?))
+	}
+
+	pub fn tx_range<'t, R: RangeBounds<K>>(
+		&self,
+		tx: &'t Transaction<'_>,
+		range: R,
+	) -> TxOpResult<TypedTxIter<'t, K, V>> {
+		Ok(TypedTxIter::new(
+			tx.range(&self.inner, encode_range(range))?,
+		))
+	}
+
+	pub fn tx_range_rev<'t, R: RangeBounds<K>>(
+		&self,
+		tx: &'t Transaction<'_>,
+		range: R,
+	) -> TxOpResult<TypedTxIter<'t, K, V>> {
+		Ok(TypedTxIter::new(
+			tx.range_rev(&self.inner, encode_range(range))?,
+		))
+	}
+}
+
+impl<K: DbBytes, V: DbBytes> From<Tree> for TypedTree<K, V> {
+	fn from(tree: Tree) -> Self {
+		Self::new(tree)
+	}
+}
+
+impl Db {
+	pub fn open_typed_tree<K: DbBytes, V: DbBytes, S: AsRef<str>>(
+		&self,
+		name: S,
+	) -> DbResult<TypedTree<K, V>> {
+		Ok(TypedTree::new(self.open_tree(name)?))
+	}
+}
+
+pub struct TypedIter<'a, K, V> {
+	inner: ValueIter<'a>,
+	_phantom: PhantomData<(K, V)>,
+}
+
+impl<'a, K, V> TypedIter<'a, K, V> {
+	fn new(inner: ValueIter<'a>) -> Self {
+		Self {
+			inner,
+			_phantom: PhantomData,
+		}
+	}
+}
+
+impl<K: DbOrdKey, V: DbBytes> Iterator for TypedIter<'_, K, V> {
+	type Item = Result<(K, V)>;
+
+	fn next(&mut self) -> Option<Self::Item> {
+		self.inner.next().map(|res| {
+			let (k, v) = res?;
+			Ok((
+				K::decode(&k).map_err(Error::from)?,
+				V::decode(&v).map_err(Error::from)?,
+			))
+		})
+	}
+}
+
+pub struct TypedTxIter<'a, K, V> {
+	inner: TxValueIter<'a>,
+	_phantom: PhantomData<(K, V)>,
+}
+
+impl<'a, K, V> TypedTxIter<'a, K, V> {
+	fn new(inner: TxValueIter<'a>) -> Self {
+		Self {
+			inner,
+			_phantom: PhantomData,
+		}
+	}
+}
+
+impl<K: DbOrdKey, V: DbBytes> Iterator for TypedTxIter<'_, K, V> {
+	type Item = TxOpResult<(K, V)>;
+
+	fn next(&mut self) -> Option<Self::Item> {
+		self.inner.next().map(|res| {
+			let (k, v) = res?;
+			Ok((
+				K::decode(&k).map_err(TxOpError::from)?,
+				V::decode(&v).map_err(TxOpError::from)?,
+			))
+		})
+	}
+}
+
+fn encode_range<K: DbOrdKey, R: RangeBounds<K>>(range: R) -> (Bound<Vec<u8>>, Bound<Vec<u8>>) {
+	(
+		encode_bound(range.start_bound()),
+		encode_bound(range.end_bound()),
+	)
+}
+
+fn encode_bound<K: DbOrdKey>(bound: Bound<&K>) -> Bound<Vec<u8>> {
+	match bound {
+		Bound::Included(k) => Bound::Included(k.encode()),
+		Bound::Excluded(k) => Bound::Excluded(k.encode()),
+		Bound::Unbounded => Bound::Unbounded,
+	}
+}

src/garage/cli/local/convert_db.rs

@@ -49,7 +49,7 @@ pub struct OpenLmdbOpt {
 
 pub(crate) fn do_conversion(args: ConvertDbOpt) -> Result<()> {
 	if args.input_engine == args.output_engine {
-		return Err(Error("input and output database engine must differ".into()));
+		return Err(DbError("input and output database engine must differ".into()).into());
 	}
 
 	let opt = OpenOpt {

src/model/index_counter.rs

@@ -163,6 +163,7 @@ impl<T: CountedItem> TableSchema for CounterTable<T> {
 
 pub struct IndexCounter<T: CountedItem> {
 	this_node: Uuid,
+	// TODO: migrate to TypedTree
 	local_counter: db::Tree,
 	pub table: Arc<Table<CounterTable<T>, TableShardedReplication>>,
 }

src/model/k2v/rpc.rs

@@ -84,6 +84,7 @@ pub struct K2VRpcHandler {
 	// Using a mutex on the local_timestamp_tree is not strictly necessary,
 	// but it helps to not try to do several inserts at the same time,
 	// which would create transaction conflicts and force many useless retries.
+	// TODO: migrate to TypedTree
 	local_timestamp_tree: Mutex<db::Tree>,
 
 	endpoint: Arc<Endpoint<K2VRpc, Self>>,

src/table/data.rs

@@ -26,15 +26,20 @@ pub struct TableData<F: TableSchema, R: TableReplication> {
 	pub instance: F,
 	pub replication: R,
 
+	// TODO: migrate to TypedTree
 	pub store: db::Tree,
 
+	// TODO: migrate to TypedTree
 	pub(crate) merkle_tree: db::Tree,
+	// TODO: migrate to TypedTree
 	pub(crate) merkle_todo: db::Tree,
 	pub(crate) merkle_todo_notify: Notify,
 
+	// TODO: migrate to TypedTree
 	pub(crate) insert_queue: db::Tree,
 	pub(crate) insert_queue_notify: Arc<Notify>,
 
+	// TODO: migrate to TypedTree
 	pub(crate) gc_todo: db::Tree,
 
 	pub(crate) metrics: TableMetrics,

src/util/data.rs

@@ -155,6 +155,21 @@ pub fn gen_uuid() -> Uuid {
 	rand::rng().random::<[u8; 32]>().into()
 }
 
+impl garage_db::DbBytes for FixedBytes32 {
+	fn encode(&self) -> Vec<u8> {
+		self.0.into()
+	}
+	fn decode(bytes: &[u8]) -> std::result::Result<Self, garage_db::DecodeError> {
+		Self::try_from(bytes).ok_or_else(|| {
+			garage_db::DecodeError(
+				format!("invalid hash: expected 32 bytes, got {}", bytes.len()).into(),
+			)
+		})
+	}
+}
+
+impl garage_db::DbOrdKey for FixedBytes32 {}
+
 #[cfg(test)]
 mod test {
 	use super::*;

src/util/error.rs

@@ -79,6 +79,18 @@ impl Error {
 	}
 }
 
+impl From<garage_db::DbError> for Error {
+	fn from(e: garage_db::DbError) -> Error {
+		Error::Db(e.into())
+	}
+}
+
+impl From<garage_db::DecodeError> for Error {
+	fn from(e: garage_db::DecodeError) -> Error {
+		Error::Db(e.into())
+	}
+}
+
 impl From<garage_db::TxError<Error>> for Error {
 	fn from(e: garage_db::TxError<Error>) -> Error {
 		match e {