11 files changed, 372 insertions, 85 deletions

diff --git a/src/block/rc.rs b/src/block/rc.rs
index 7d85f67e..e0b952fd 100644
--- a/src/block/rc.rs
+++ b/src/block/rc.rs
@@ -20,7 +20,7 @@ impl BlockRc {
 	/// Increment the reference counter associated to a hash.
 	/// Returns true if the RC goes from zero to nonzero.
 	pub(crate) fn block_incref(&self, hash: &Hash) -> Result<bool, Error> {
-		let old_rc = self.rc.db().transaction(|tx| {
+		let old_rc = self.rc.db().transaction(|mut tx| {
 			let old_rc = RcEntry::parse_opt(tx.get(&self.rc, &hash)?);
 			match old_rc.increment().serialize() {
 				Some(x) => {
@@ -36,7 +36,7 @@ impl BlockRc {
 	/// Decrement the reference counter associated to a hash.
 	/// Returns true if the RC is now zero.
 	pub(crate) fn block_decref(&self, hash: &Hash) -> Result<bool, Error> {
-		let new_rc = self.rc.db().transaction(|tx| {
+		let new_rc = self.rc.db().transaction(|mut tx| {
 			let new_rc = RcEntry::parse_opt(tx.get(&self.rc, &hash)?).decrement();
 			match new_rc.serialize() {
 				Some(x) => {
@@ -60,7 +60,7 @@ impl BlockRc {
 	/// deletion time has passed
 	pub(crate) fn clear_deleted_block_rc(&self, hash: &Hash) -> Result<(), Error> {
 		let now = now_msec();
-		self.rc.db().transaction(|tx| {
+		self.rc.db().transaction(|mut tx| {
 			let rcval = RcEntry::parse_opt(tx.get(&self.rc, &hash)?);
 			match rcval {
 				RcEntry::Deletable { at_time } if now > at_time => {
diff --git a/src/db/Cargo.toml b/src/db/Cargo.toml
index 36b96229..b4601ff7 100644
--- a/src/db/Cargo.toml
+++ b/src/db/Cargo.toml
@@ -21,8 +21,9 @@ err-derive = "0.3"
 hexdump = "0.1"
 log = "0.4"
 
-sled = "0.34"
+lmdb = "0.8"
 rusqlite = "0.27"
+sled = "0.34"
 
 # cli deps
 clap = { version = "3.1.18", optional = true, features = ["derive", "env"] }
diff --git a/src/db/lib.rs b/src/db/lib.rs
index 045c16c5..86042eaf 100644
--- a/src/db/lib.rs
+++ b/src/db/lib.rs
@@ -1,3 +1,4 @@
+pub mod lmdb_adapter;
 pub mod sled_adapter;
 pub mod sqlite_adapter;
 
@@ -15,8 +16,7 @@ use err_derive::Error;
 #[derive(Clone)]
 pub struct Db(pub(crate) Arc<dyn IDb>);
 
-#[derive(Clone, Copy)]
-pub struct Transaction<'a>(pub(crate) &'a dyn ITx<'a>);
+pub struct Transaction<'a>(pub(crate) &'a mut dyn ITx);
 
 #[derive(Clone)]
 pub struct Tree(pub(crate) Arc<dyn IDb>, pub(crate) usize);
@@ -271,7 +271,7 @@ impl Tree {
 
 #[allow(clippy::len_without_is_empty)]
 impl<'a> Transaction<'a> {
-	pub fn get<T: AsRef<[u8]>>(&self, tree: &Tree, key: T) -> Result<Option<Value<'a>>> {
+	pub fn get<T: AsRef<[u8]>>(&self, tree: &Tree, key: T) -> Result<Option<Value<'_>>> {
 		self.0.get(tree.1, key.as_ref())
 	}
 	pub fn len(&self, tree: &Tree) -> Result<usize> {
@@ -279,25 +279,25 @@ impl<'a> Transaction<'a> {
 	}
 
 	pub fn insert<T: AsRef<[u8]>, U: AsRef<[u8]>>(
-		&self,
+		&mut self,
 		tree: &Tree,
 		key: T,
 		value: U,
 	) -> Result<()> {
 		self.0.insert(tree.1, key.as_ref(), value.as_ref())
 	}
-	pub fn remove<T: AsRef<[u8]>>(&self, tree: &Tree, key: T) -> Result<bool> {
+	pub fn remove<T: AsRef<[u8]>>(&mut self, tree: &Tree, key: T) -> Result<bool> {
 		self.0.remove(tree.1, key.as_ref())
 	}
 
-	pub fn iter(&self, tree: &Tree) -> Result<ValueIter<'a>> {
+	pub fn iter(&self, tree: &Tree) -> Result<ValueIter<'_>> {
 		self.0.iter(tree.1)
 	}
-	pub fn iter_rev(&self, tree: &Tree) -> Result<ValueIter<'a>> {
+	pub fn iter_rev(&self, tree: &Tree) -> Result<ValueIter<'_>> {
 		self.0.iter_rev(tree.1)
 	}
 
-	pub fn range<K, R>(&self, tree: &Tree, range: R) -> Result<ValueIter<'a>>
+	pub fn range<K, R>(&self, tree: &Tree, range: R) -> Result<ValueIter<'_>>
 	where
 		K: AsRef<[u8]>,
 		R: RangeBounds<K>,
@@ -306,7 +306,7 @@ impl<'a> Transaction<'a> {
 		let eb = range.end_bound();
 		self.0.range(tree.1, get_bound(sb), get_bound(eb))
 	}
-	pub fn range_rev<K, R>(&self, tree: &Tree, range: R) -> Result<ValueIter<'a>>
+	pub fn range_rev<K, R>(&self, tree: &Tree, range: R) -> Result<ValueIter<'_>>
 	where
 		K: AsRef<[u8]>,
 		R: RangeBounds<K>,
@@ -358,32 +358,32 @@ pub(crate) trait IDb: Send + Sync {
 	fn transaction(&self, f: &dyn ITxFn) -> TxResult<(), ()>;
 }
 
-pub(crate) trait ITx<'a> {
-	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'a>>>;
+pub(crate) trait ITx {
+	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'_>>>;
 	fn len(&self, tree: usize) -> Result<usize>;
 
-	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<()>;
-	fn remove(&self, tree: usize, key: &[u8]) -> Result<bool>;
+	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> Result<()>;
+	fn remove(&mut self, tree: usize, key: &[u8]) -> Result<bool>;
 
-	fn iter(&self, tree: usize) -> Result<ValueIter<'a>>;
-	fn iter_rev(&self, tree: usize) -> Result<ValueIter<'a>>;
+	fn iter(&self, tree: usize) -> Result<ValueIter<'_>>;
+	fn iter_rev(&self, tree: usize) -> Result<ValueIter<'_>>;
 
 	fn range<'r>(
 		&self,
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'a>>;
+	) -> Result<ValueIter<'_>>;
 	fn range_rev<'r>(
 		&self,
 		tree: usize,
 		low: Bound<&'r [u8]>,
 		high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'a>>;
+	) -> Result<ValueIter<'_>>;
 }
 
 pub(crate) trait ITxFn {
-	fn try_on<'a>(&'a self, tx: &'a dyn ITx<'a>) -> TxFnResult;
+	fn try_on(&self, tx: &mut dyn ITx) -> TxFnResult;
 }
 
 pub(crate) enum TxFnResult {
@@ -404,7 +404,7 @@ impl<F, R, E> ITxFn for TxFn<F, R, E>
 where
 	F: Fn(Transaction<'_>) -> TxResult<R, E>,
 {
-	fn try_on<'a>(&'a self, tx: &'a dyn ITx<'a>) -> TxFnResult {
+	fn try_on(&self, tx: &mut dyn ITx) -> TxFnResult {
 		let res = (self.function)(Transaction(tx));
 		let res2 = match &res {
 			Ok(_) => TxFnResult::Ok,
diff --git a/src/db/lmdb_adapter.rs b/src/db/lmdb_adapter.rs
new file mode 100644
index 00000000..caf21517
--- /dev/null
+++ b/src/db/lmdb_adapter.rs
@@ -0,0 +1,270 @@
+use core::marker::PhantomPinned;
+use core::ops::Bound;
+use core::pin::Pin;
+use core::ptr::NonNull;
+
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::sync::{Arc, RwLock};
+
+use lmdb::{
+	Database, DatabaseFlags, Environment, RoTransaction, RwTransaction, Transaction, WriteFlags,
+};
+
+use crate::{
+	Db, Error, IDb, ITx, ITxFn, IValue, Result, TxError, TxFnResult, TxResult, Value, ValueIter,
+};
+
+pub use lmdb;
+
+// -- err
+
+impl From<lmdb::Error> for Error {
+	fn from(e: lmdb::Error) -> Error {
+		Error(format!("LMDB: {}", e).into())
+	}
+}
+
+impl<T> From<lmdb::Error> for TxError<T> {
+	fn from(e: lmdb::Error) -> TxError<T> {
+		TxError::Db(e.into())
+	}
+}
+
+// -- db
+
+pub struct LmdbDb {
+	db: lmdb::Environment,
+	trees: RwLock<(Vec<lmdb::Database>, HashMap<String, usize>)>,
+}
+
+impl LmdbDb {
+	pub fn init(db: lmdb::Environment) -> Db {
+		let s = Self {
+			db,
+			trees: RwLock::new((Vec::new(), HashMap::new())),
+		};
+		Db(Arc::new(s))
+	}
+
+	fn get_tree(&self, i: usize) -> Result<lmdb::Database> {
+		self.trees
+			.read()
+			.unwrap()
+			.0
+			.get(i)
+			.cloned()
+			.ok_or_else(|| Error("invalid tree id".into()))
+	}
+}
+
+impl IDb for LmdbDb {
+	fn open_tree(&self, name: &str) -> Result<usize> {
+		let mut trees = self.trees.write().unwrap();
+		if let Some(i) = trees.1.get(name) {
+			Ok(*i)
+		} else {
+			let tree = self.db.create_db(Some(name), DatabaseFlags::empty())?;
+			let i = trees.0.len();
+			trees.0.push(tree);
+			trees.1.insert(name.to_string(), i);
+			Ok(i)
+		}
+	}
+
+	fn list_trees(&self) -> Result<Vec<String>> {
+		unimplemented!()
+	}
+
+	// ----
+
+	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'_>>> {
+		let tree = self.get_tree(tree)?;
+
+		let res = TxAndValue {
+			tx: self.db.begin_ro_txn()?,
+			value: NonNull::dangling(),
+			_pin: PhantomPinned,
+		};
+		let mut boxed = Box::pin(res);
+
+		unsafe {
+			let tx = NonNull::from(&boxed.tx);
+			let val = match tx.as_ref().get(tree, &key) {
+				Err(lmdb::Error::NotFound) => return Ok(None),
+				v => v?,
+			};
+
+			let mut_ref: Pin<&mut TxAndValue<'_>> = Pin::as_mut(&mut boxed);
+			Pin::get_unchecked_mut(mut_ref).value = NonNull::from(&val);
+		}
+
+		Ok(Some(Value(Box::new(TxAndValuePin(boxed)))))
+	}
+
+	fn remove(&self, tree: usize, key: &[u8]) -> Result<bool> {
+		unimplemented!()
+	}
+
+	fn len(&self, tree: usize) -> Result<usize> {
+		unimplemented!()
+	}
+
+	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
+		let tree = self.get_tree(tree)?;
+		let mut tx = self.db.begin_rw_txn()?;
+		tx.put(tree, &key, &value, WriteFlags::empty())?;
+		tx.commit()?;
+		Ok(())
+	}
+
+	fn iter(&self, tree: usize) -> Result<ValueIter<'_>> {
+		unimplemented!()
+	}
+
+	fn iter_rev(&self, tree: usize) -> Result<ValueIter<'_>> {
+		unimplemented!()
+	}
+
+	fn range<'r>(
+		&self,
+		tree: usize,
+		low: Bound<&'r [u8]>,
+		high: Bound<&'r [u8]>,
+	) -> Result<ValueIter<'_>> {
+		unimplemented!()
+	}
+	fn range_rev<'r>(
+		&self,
+		tree: usize,
+		low: Bound<&'r [u8]>,
+		high: Bound<&'r [u8]>,
+	) -> Result<ValueIter<'_>> {
+		unimplemented!()
+	}
+
+	// ----
+
+	fn transaction(&self, f: &dyn ITxFn) -> TxResult<(), ()> {
+		let trees = self.trees.read().unwrap();
+		let mut tx = LmdbTx {
+			trees: &trees.0[..],
+			tx: self.db.begin_rw_txn()?,
+		};
+
+		let res = f.try_on(&mut tx);
+		match res {
+			TxFnResult::Ok => {
+				tx.tx.commit()?;
+				Ok(())
+			}
+			TxFnResult::Abort => {
+				tx.tx.abort();
+				Err(TxError::Abort(()))
+			}
+			TxFnResult::DbErr => {
+				tx.tx.abort();
+				Err(TxError::Db(Error(
+					"(this message will be discarded)".into(),
+				)))
+			}
+		}
+	}
+}
+
+// ----
+
+struct LmdbTx<'a, 'db> {
+	trees: &'db [Database],
+	tx: RwTransaction<'a>,
+}
+
+impl<'a, 'db> LmdbTx<'a, 'db> {
+	fn get_tree(&self, i: usize) -> Result<&Database> {
+		self.trees.get(i).ok_or_else(|| {
+			Error(
+				"invalid tree id (it might have been openned after the transaction started)".into(),
+			)
+		})
+	}
+}
+
+impl<'a, 'db> ITx for LmdbTx<'a, 'db> {
+	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'_>>> {
+		let tree = self.get_tree(tree)?;
+		match self.tx.get::<'a, _>(*tree, &key) {
+			Err(lmdb::Error::NotFound) => Ok(None),
+			Err(e) => Err(e.into()),
+			Ok(v) => Ok(Some(Value(Box::new(v)))),
+		}
+	}
+	fn len(&self, _tree: usize) -> Result<usize> {
+		unimplemented!(".len() in transaction not supported with LMDB backend")
+	}
+
+	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
+		let tree = self.get_tree(tree)?;
+		self.tx.put(*tree, &key, &value, WriteFlags::empty())?;
+		Ok(())
+	}
+	fn remove(&mut self, tree: usize, key: &[u8]) -> Result<bool> {
+		let tree = self.get_tree(tree)?;
+		match self.tx.del::<'a, _>(*tree, &key, None) {
+			Ok(()) => Ok(true),
+			Err(lmdb::Error::NotFound) => Ok(false),
+			Err(e) => Err(e.into()),
+		}
+	}
+
+	fn iter(&self, _tree: usize) -> Result<ValueIter<'_>> {
+		unimplemented!("Iterators in transactions not supported with LMDB backend");
+	}
+	fn iter_rev(&self, _tree: usize) -> Result<ValueIter<'_>> {
+		unimplemented!("Iterators in transactions not supported with LMDB backend");
+	}
+
+	fn range<'r>(
+		&self,
+		_tree: usize,
+		_low: Bound<&'r [u8]>,
+		_high: Bound<&'r [u8]>,
+	) -> Result<ValueIter<'_>> {
+		unimplemented!("Iterators in transactions not supported with LMDB backend");
+	}
+	fn range_rev<'r>(
+		&self,
+		_tree: usize,
+		_low: Bound<&'r [u8]>,
+		_high: Bound<&'r [u8]>,
+	) -> Result<ValueIter<'_>> {
+		unimplemented!("Iterators in transactions not supported with LMDB backend");
+	}
+}
+
+// ----
+
+struct TxAndValue<'a> {
+	tx: RoTransaction<'a>,
+	value: NonNull<&'a [u8]>,
+	_pin: PhantomPinned,
+}
+
+struct TxAndValuePin<'a>(Pin<Box<TxAndValue<'a>>>);
+
+impl<'a> IValue<'a> for TxAndValuePin<'a> {
+	fn take_maybe(&mut self) -> Vec<u8> {
+		self.as_ref().to_vec()
+	}
+}
+
+impl<'a> AsRef<[u8]> for TxAndValuePin<'a> {
+	fn as_ref(&self) -> &[u8] {
+		unsafe { self.0.value.as_ref() }
+	}
+}
+
+impl<'a> std::borrow::Borrow<[u8]> for TxAndValuePin<'a> {
+	fn borrow(&self) -> &[u8] {
+		self.as_ref()
+	}
+}
diff --git a/src/db/sled_adapter.rs b/src/db/sled_adapter.rs
index 3388b0ca..2953785e 100644
--- a/src/db/sled_adapter.rs
+++ b/src/db/sled_adapter.rs
@@ -19,7 +19,7 @@ pub use sled;
 
 impl From<sled::Error> for Error {
 	fn from(e: sled::Error) -> Error {
-		Error(format!("{}", e).into())
+		Error(format!("Sled: {}", e).into())
 	}
 }
 
@@ -162,11 +162,11 @@ impl IDb for SledDb {
 	fn transaction(&self, f: &dyn ITxFn) -> TxResult<(), ()> {
 		let trees = self.trees.read().unwrap();
 		let res = trees.0.transaction(|txtrees| {
-			let tx = SledTx {
+			let mut tx = SledTx {
 				trees: txtrees,
 				err: Cell::new(None),
 			};
-			match f.try_on(&tx) {
+			match f.try_on(&mut tx) {
 				TxFnResult::Ok => {
 					assert!(tx.err.into_inner().is_none());
 					Ok(())
@@ -217,8 +217,8 @@ impl<'a> SledTx<'a> {
 	}
 }
 
-impl<'a> ITx<'a> for SledTx<'a> {
-	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'a>>> {
+impl<'a> ITx for SledTx<'a> {
+	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'_>>> {
 		let tree = self.get_tree(tree)?;
 		let tmp = self.save_error(tree.get(key))?;
 		Ok(tmp.map(From::from))
@@ -227,20 +227,20 @@ impl<'a> ITx<'a> for SledTx<'a> {
 		unimplemented!(".len() in transaction not supported with Sled backend")
 	}
 
-	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
+	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
 		let tree = self.get_tree(tree)?;
 		self.save_error(tree.insert(key, value))?;
 		Ok(())
 	}
-	fn remove(&self, tree: usize, key: &[u8]) -> Result<bool> {
+	fn remove(&mut self, tree: usize, key: &[u8]) -> Result<bool> {
 		let tree = self.get_tree(tree)?;
 		Ok(self.save_error(tree.remove(key))?.is_some())
 	}
 
-	fn iter(&self, _tree: usize) -> Result<ValueIter<'a>> {
+	fn iter(&self, _tree: usize) -> Result<ValueIter<'_>> {
 		unimplemented!("Iterators in transactions not supported with Sled backend");
 	}
-	fn iter_rev(&self, _tree: usize) -> Result<ValueIter<'a>> {
+	fn iter_rev(&self, _tree: usize) -> Result<ValueIter<'_>> {
 		unimplemented!("Iterators in transactions not supported with Sled backend");
 	}
 
@@ -249,7 +249,7 @@ impl<'a> ITx<'a> for SledTx<'a> {
 		_tree: usize,
 		_low: Bound<&'r [u8]>,
 		_high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'a>> {
+	) -> Result<ValueIter<'_>> {
 		unimplemented!("Iterators in transactions not supported with Sled backend");
 	}
 	fn range_rev<'r>(
@@ -257,7 +257,7 @@ impl<'a> ITx<'a> for SledTx<'a> {
 		_tree: usize,
 		_low: Bound<&'r [u8]>,
 		_high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'a>> {
+	) -> Result<ValueIter<'_>> {
 		unimplemented!("Iterators in transactions not supported with Sled backend");
 	}
 }
diff --git a/src/db/sqlite_adapter.rs b/src/db/sqlite_adapter.rs
index 4f79b34b..9f2bf919 100644
--- a/src/db/sqlite_adapter.rs
+++ b/src/db/sqlite_adapter.rs
@@ -17,7 +17,7 @@ pub use rusqlite;
 
 impl From<rusqlite::Error> for Error {
 	fn from(e: rusqlite::Error) -> Error {
-		Error(format!("{}", e).into())
+		Error(format!("Sqlite: {}", e).into())
 	}
 }
 
@@ -235,11 +235,11 @@ impl IDb for SqliteDb {
 		let mut db = self.db.lock().unwrap();
 		trace!("transaction: lock acquired");
 
-		let tx = SqliteTx {
+		let mut tx = SqliteTx {
 			tx: db.transaction()?,
 			trees: trees.as_ref(),
 		};
-		let res = match f.try_on(&tx) {
+		let res = match f.try_on(&mut tx) {
 			TxFnResult::Ok => {
 				tx.tx.commit()?;
 				Ok(())
@@ -278,8 +278,8 @@ impl<'a> SqliteTx<'a> {
 	}
 }
 
-impl<'a> ITx<'a> for SqliteTx<'a> {
-	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'a>>> {
+impl<'a> ITx for SqliteTx<'a> {
+	fn get(&self, tree: usize, key: &[u8]) -> Result<Option<Value<'_>>> {
 		let tree = self.get_tree(tree)?;
 		let mut stmt = self
 			.tx
@@ -300,7 +300,7 @@ impl<'a> ITx<'a> for SqliteTx<'a> {
 		}
 	}
 
-	fn insert(&self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
+	fn insert(&mut self, tree: usize, key: &[u8], value: &[u8]) -> Result<()> {
 		let tree = self.get_tree(tree)?;
 		self.tx.execute(
 			&format!("INSERT OR REPLACE INTO {} (k, v) VALUES (?1, ?2)", tree),
@@ -308,7 +308,7 @@ impl<'a> ITx<'a> for SqliteTx<'a> {
 		)?;
 		Ok(())
 	}
-	fn remove(&self, tree: usize, key: &[u8]) -> Result<bool> {
+	fn remove(&mut self, tree: usize, key: &[u8]) -> Result<bool> {
 		let tree = self.get_tree(tree)?;
 		let res = self
 			.tx
@@ -316,10 +316,10 @@ impl<'a> ITx<'a> for SqliteTx<'a> {
 		Ok(res > 0)
 	}
 
-	fn iter(&self, _tree: usize) -> Result<ValueIter<'a>> {
+	fn iter(&self, _tree: usize) -> Result<ValueIter<'_>> {
 		unimplemented!();
 	}
-	fn iter_rev(&self, _tree: usize) -> Result<ValueIter<'a>> {
+	fn iter_rev(&self, _tree: usize) -> Result<ValueIter<'_>> {
 		unimplemented!();
 	}
 
@@ -328,7 +328,7 @@ impl<'a> ITx<'a> for SqliteTx<'a> {
 		_tree: usize,
 		_low: Bound<&'r [u8]>,
 		_high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'a>> {
+	) -> Result<ValueIter<'_>> {
 		unimplemented!();
 	}
 	fn range_rev<'r>(
@@ -336,7 +336,7 @@ impl<'a> ITx<'a> for SqliteTx<'a> {
 		_tree: usize,
 		_low: Bound<&'r [u8]>,
 		_high: Bound<&'r [u8]>,
-	) -> Result<ValueIter<'a>> {
+	) -> Result<ValueIter<'_>> {
 		unimplemented!();
 	}
 }
diff --git a/src/db/test.rs b/src/db/test.rs
index 75200cf1..e5b83ab5 100644
--- a/src/db/test.rs
+++ b/src/db/test.rs
@@ -1,5 +1,6 @@
 use crate::*;
 
+use crate::lmdb_adapter::LmdbDb;
 use crate::sled_adapter::SledDb;
 use crate::sqlite_adapter::SqliteDb;
 
@@ -16,7 +17,7 @@ fn test_suite(db: Db) {
 	tree.insert(ka, va).unwrap();
 	assert_eq!(tree.get(ka).unwrap().unwrap(), va);
 
-	let res = db.transaction::<_, (), _>(|tx| {
+	let res = db.transaction::<_, (), _>(|mut tx| {
 		assert_eq!(tx.get(&tree, ka).unwrap().unwrap(), va);
 
 		tx.insert(&tree, ka, vb).unwrap();
@@ -28,7 +29,7 @@ fn test_suite(db: Db) {
 	assert!(matches!(res, Ok(12)));
 	assert_eq!(tree.get(ka).unwrap().unwrap(), vb);
 
-	let res = db.transaction::<(), _, _>(|tx| {
+	let res = db.transaction::<(), _, _>(|mut tx| {
 		assert_eq!(tx.get(&tree, ka).unwrap().unwrap(), vb);
 
 		tx.insert(&tree, ka, vc).unwrap();
@@ -79,6 +80,18 @@ fn test_suite(db: Db) {
 }
 
 #[test]
+fn test_lmdb_db() {
+	let path = mktemp::Temp::new_dir().unwrap();
+	let db = lmdb::Environment::new()
+		.set_max_dbs(100)
+		.open(&path)
+		.unwrap();
+	let db = LmdbDb::init(db);
+	test_suite(db);
+	drop(path);
+}
+
+#[test]
 fn test_sled_db() {
 	let path = mktemp::Temp::new_dir().unwrap();
 	let db = SledDb::init(sled::open(path.to_path_buf()).unwrap());
diff --git a/src/model/index_counter.rs b/src/model/index_counter.rs
index 9e343e5f..d8c1229a 100644
--- a/src/model/index_counter.rs
+++ b/src/model/index_counter.rs
@@ -179,7 +179,7 @@ impl<T: CounterSchema> IndexCounter<T> {
 	pub fn count(&self, pk: &T::P, sk: &T::S, counts: &[(&str, i64)]) -> Result<(), Error> {
 		let tree_key = self.table.data.tree_key(pk, sk);
 
-		let new_entry = self.local_counter.db().transaction(|tx| {
+		let new_entry = self.local_counter.db().transaction(|mut tx| {
 			let mut entry = match tx.get(&self.local_counter, &tree_key[..])? {
 				Some(old_bytes) => rmp_serde::decode::from_slice::<LocalCounterEntry>(&old_bytes)
 					.map_err(Error::RmpDecode)
diff --git a/src/table/data.rs b/src/table/data.rs
index 17402bb6..cca96f68 100644
--- a/src/table/data.rs
+++ b/src/table/data.rs
@@ -182,7 +182,7 @@ where
 		tree_key: &[u8],
 		f: impl Fn(Option<F::E>) -> F::E,
 	) -> Result<Option<F::E>, Error> {
-		let changed = self.store.db().transaction(|tx| {
+		let changed = self.store.db().transaction(|mut tx| {
 			let (old_entry, old_bytes, new_entry) = match tx.get(&self.store, tree_key)? {
 				Some(old_bytes) => {
 					let old_entry = self.decode_entry(&old_bytes).map_err(db::TxError::Abort)?;
@@ -203,6 +203,7 @@ where
 				.map_err(Error::RmpEncode)
 				.map_err(db::TxError::Abort)?;
 			let encoding_changed = Some(&new_bytes[..]) != old_bytes.as_ref().map(|x| &x[..]);
+			drop(old_bytes);
 
 			if value_changed || encoding_changed {
 				let new_bytes_hash = blake2sum(&new_bytes[..]);
@@ -241,15 +242,16 @@ where
 	}
 
 	pub(crate) fn delete_if_equal(self: &Arc<Self>, k: &[u8], v: &[u8]) -> Result<bool, Error> {
-		let removed = self.store.db().transaction(|tx| {
-			if let Some(cur_v) = tx.get(&self.store, k)? {
-				if cur_v == v {
-					tx.remove(&self.store, k)?;
-					tx.insert(&self.merkle_todo, k, vec![])?;
-					return Ok(true);
-				}
+		let removed = self.store.db().transaction(|mut tx| {
+			let remove = match tx.get(&self.store, k)? {
+				Some(cur_v) if cur_v == v => true,
+				_ => false,
+			};
+			if remove {
+				tx.remove(&self.store, k)?;
+				tx.insert(&self.merkle_todo, k, vec![])?;
 			}
-			Ok(false)
+			Ok(remove)
 		})?;
 
 		if removed {
@@ -267,15 +269,16 @@ where
 		k: &[u8],
 		vhash: Hash,
 	) -> Result<bool, Error> {
-		let removed = self.store.db().transaction(|tx| {
-			if let Some(cur_v) = tx.get(&self.store, k)? {
-				if blake2sum(&cur_v[..]) == vhash {
-					tx.remove(&self.store, k)?;
-					tx.insert(&self.merkle_todo, k, vec![])?;
-					return Ok(Some(cur_v.into_vec()));
-				}
+		let removed = self.store.db().transaction(|mut tx| {
+			let remove_v = match tx.get(&self.store, k)? {
+				Some(cur_v) if blake2sum(&cur_v[..]) == vhash => Some(cur_v.into_vec()),
+				_ => None,
+			};
+			if remove_v.is_some() {
+				tx.remove(&self.store, k)?;
+				tx.insert(&self.merkle_todo, k, vec![])?;
 			}
-			Ok(None)
+			Ok(remove_v)
 		})?;
 
 		if let Some(old_v) = removed {
diff --git a/src/table/gc.rs b/src/table/gc.rs
index 260fecfa..e2611389 100644
--- a/src/table/gc.rs
+++ b/src/table/gc.rs
@@ -376,13 +376,13 @@ impl GcTodoEntry {
 	/// what we have to do is still the same
 	pub(crate) fn remove_if_equal(&self, gc_todo_tree: &db::Tree) -> Result<(), Error> {
 		let key = self.todo_table_key();
-		gc_todo_tree.db().transaction(|tx| {
-			let old_val = tx.get(gc_todo_tree, &key)?;
-			match old_val {
-				Some(ov) if ov == self.value_hash.as_slice() => {
-					tx.remove(gc_todo_tree, &key)?;
-				}
-				_ => (),
+		gc_todo_tree.db().transaction(|mut tx| {
+			let remove = match tx.get(gc_todo_tree, &key)? {
+				Some(ov) if ov == self.value_hash.as_slice() => true,
+				_ => false,
+			};
+			if remove {
+				tx.remove(gc_todo_tree, &key)?;
 			}
 			tx.commit(())
 		})?;
diff --git a/src/table/merkle.rs b/src/table/merkle.rs
index 8c574d09..92e1445b 100644
--- a/src/table/merkle.rs
+++ b/src/table/merkle.rs
@@ -137,17 +137,17 @@ where
 		self.data
 			.merkle_tree
 			.db()
-			.transaction(|tx| self.update_item_rec(tx, k, &khash, &key, new_vhash))?;
-
-		let deleted = self.data.merkle_todo.db().transaction(|tx| {
-			let old_val = tx.get(&self.data.merkle_todo, k)?;
-			match old_val {
-				Some(ov) if ov == vhash_by => {
-					tx.remove(&self.data.merkle_todo, k)?;
-					tx.commit(true)
-				}
-				_ => tx.commit(false),
+			.transaction(|mut tx| self.update_item_rec(&mut tx, k, &khash, &key, new_vhash))?;
+
+		let deleted = self.data.merkle_todo.db().transaction(|mut tx| {
+			let remove = match tx.get(&self.data.merkle_todo, k)? {
+				Some(ov) if ov == vhash_by => true,
+				_ => false,
+			};
+			if remove {
+				tx.remove(&self.data.merkle_todo, k)?;
 			}
+			Ok(remove)
 		})?;
 
 		if !deleted {
@@ -162,7 +162,7 @@ where
 
 	fn update_item_rec(
 		&self,
-		tx: db::Transaction<'_>,
+		tx: &mut db::Transaction<'_>,
 		k: &[u8],
 		khash: &Hash,
 		key: &MerkleNodeKey,
@@ -288,7 +288,7 @@ where
 
 	fn read_node_txn(
 		&self,
-		tx: db::Transaction<'_>,
+		tx: &mut db::Transaction<'_>,
 		k: &MerkleNodeKey,
 	) -> db::TxResult<MerkleNode, Error> {
 		let ent = tx.get(&self.data.merkle_tree, k.encode())?;
@@ -297,7 +297,7 @@ where
 
 	fn put_node_txn(
 		&self,
-		tx: db::Transaction<'_>,
+		tx: &mut db::Transaction<'_>,
 		k: &MerkleNodeKey,
 		v: &MerkleNode,
 	) -> db::TxResult<Hash, Error> {