Working on a better database abstraction (#931)

* Working on a better database abstraction

After [this question in the chat](https://matrix.to/#/!oJFtttFHGfnTGrIjvD:matrix.cashu.space/$oJFtttFHGfnTGrIjvD:matrix.cashu.space/$I5ZtjJtBM0ctltThDYpoCwClZFlM6PHzf8q2Rjqmso8)
regarding a database transaction within the same function, I realized a few
design flaws in our SQL database abstraction, particularly regarding
transactions.

1. Our upper abstraction got it right, where a transaction is bound with `&mut
   self`, so Rust knows how to handle its lifetime with' async/await'.
2. The raw database does not; instead, it returns &self, and beginning a
   transaction takes &self as well, which is problematic for Rust, but that's not
   all. It is fundamentally wrong. A transaction should take &mut self when
   beginning a transaction, as that connection is bound to a transaction and
   should not be returned to the pool. Currently, that responsibility lies with
   the implementor. If a mistake is made, a transaction could be executed in two
   or more connections.
3. The way a database is bound to our store layer is through a single struct,
   which may or may not internally utilize our connection pool. This is also
   another design flow, in this PR, a connection pool is owned, and to use a
   connection, it should be requested, and that connection is reference with
   mutable when beginning a transaction

* Improve the abstraction with fewer generics

As suggested by @thesimplekid

* Add BEGIN IMMEDIATE for SQLite

crates/cdk-sql-common/Cargo.toml

@@ -23,6 +23,7 @@ cdk-common = { workspace = true, features = ["test"] }
 bitcoin.workspace = true
 thiserror.workspace = true
 tracing.workspace = true
+tokio.workspace = true
 serde.workspace = true
 serde_json.workspace = true
 lightning-invoice.workspace = true

crates/cdk-sql-common/src/common.rs

@@ -3,11 +3,14 @@ use crate::stmt::query;
 
 /// Migrates the migration generated by `build.rs`
 #[inline(always)]
-pub async fn migrate<C: DatabaseExecutor>(
+pub async fn migrate<C>(
     conn: &C,
     db_prefix: &str,
     migrations: &[(&str, &str, &str)],
-) -> Result<(), cdk_common::database::Error> {
+) -> Result<(), cdk_common::database::Error>
+where
+    C: DatabaseExecutor,
+{
     query(
         r#"
            CREATE TABLE IF NOT EXISTS migrations (

crates/cdk-sql-common/src/database.rs

@@ -1,10 +1,12 @@
 //! Database traits definition
 
 use std::fmt::Debug;
+use std::marker::PhantomData;
+use std::ops::{Deref, DerefMut};
 
 use cdk_common::database::Error;
 
-use crate::stmt::{Column, Statement};
+use crate::stmt::{query, Column, Statement};
 
 /// Database Executor
 ///
@@ -32,22 +34,170 @@ pub trait DatabaseExecutor: Debug + Sync + Send {
 
 /// Database transaction trait
 #[async_trait::async_trait]
-pub trait DatabaseTransaction<'a>: Debug + DatabaseExecutor + Send + Sync {
+pub trait DatabaseTransaction<DB>
+where
+    DB: DatabaseExecutor,
+{
     /// Consumes the current transaction committing the changes
-    async fn commit(self) -> Result<(), Error>;
+    async fn commit(conn: &mut DB) -> Result<(), Error>;
+
+    /// Begin a transaction
+    async fn begin(conn: &mut DB) -> Result<(), Error>;
 
     /// Consumes the transaction rolling back all changes
-    async fn rollback(self) -> Result<(), Error>;
+    async fn rollback(conn: &mut DB) -> Result<(), Error>;
+}
+
+/// Database connection with a transaction
+#[derive(Debug)]
+pub struct ConnectionWithTransaction<DB, W>
+where
+    DB: DatabaseConnector + 'static,
+    W: Debug + Deref<Target = DB> + DerefMut<Target = DB> + Send + Sync + 'static,
+{
+    inner: Option<W>,
+}
+
+impl<DB, W> ConnectionWithTransaction<DB, W>
+where
+    DB: DatabaseConnector,
+    W: Debug + Deref<Target = DB> + DerefMut<Target = DB> + Send + Sync + 'static,
+{
+    /// Creates a new transaction
+    pub async fn new(mut inner: W) -> Result<Self, Error> {
+        DB::Transaction::begin(inner.deref_mut()).await?;
+        Ok(Self { inner: Some(inner) })
+    }
+
+    /// Commits the transaction consuming it and releasing the connection back to the pool (or
+    /// disconnecting)
+    pub async fn commit(mut self) -> Result<(), Error> {
+        let mut conn = self
+            .inner
+            .take()
+            .ok_or(Error::Internal("Missing connection".to_owned()))?;
+
+        DB::Transaction::commit(&mut conn).await?;
+
+        Ok(())
+    }
+
+    /// Rollback the transaction consuming it and releasing the connection back to the pool (or
+    /// disconnecting)
+    pub async fn rollback(mut self) -> Result<(), Error> {
+        let mut conn = self
+            .inner
+            .take()
+            .ok_or(Error::Internal("Missing connection".to_owned()))?;
+
+        DB::Transaction::rollback(&mut conn).await?;
+
+        Ok(())
+    }
+}
+
+impl<DB, W> Drop for ConnectionWithTransaction<DB, W>
+where
+    DB: DatabaseConnector,
+    W: Debug + Deref<Target = DB> + DerefMut<Target = DB> + Send + Sync + 'static,
+{
+    fn drop(&mut self) {
+        if let Some(mut conn) = self.inner.take() {
+            tokio::spawn(async move {
+                let _ = DB::Transaction::rollback(conn.deref_mut()).await;
+            });
+        }
+    }
+}
+
+#[async_trait::async_trait]
+impl<DB, W> DatabaseExecutor for ConnectionWithTransaction<DB, W>
+where
+    DB: DatabaseConnector,
+    W: Debug + Deref<Target = DB> + DerefMut<Target = DB> + Send + Sync + 'static,
+{
+    fn name() -> &'static str {
+        "Transaction"
+    }
+
+    /// Executes a query and returns the affected rows
+    async fn execute(&self, statement: Statement) -> Result<usize, Error> {
+        self.inner
+            .as_ref()
+            .ok_or(Error::Internal("Missing internal connection".to_owned()))?
+            .execute(statement)
+            .await
+    }
+
+    /// Runs the query and returns the first row or None
+    async fn fetch_one(&self, statement: Statement) -> Result<Option<Vec<Column>>, Error> {
+        self.inner
+            .as_ref()
+            .ok_or(Error::Internal("Missing internal connection".to_owned()))?
+            .fetch_one(statement)
+            .await
+    }
+
+    /// Runs the query and returns the first row or None
+    async fn fetch_all(&self, statement: Statement) -> Result<Vec<Vec<Column>>, Error> {
+        self.inner
+            .as_ref()
+            .ok_or(Error::Internal("Missing internal connection".to_owned()))?
+            .fetch_all(statement)
+            .await
+    }
+
+    /// Fetches the first row and column from a query
+    async fn pluck(&self, statement: Statement) -> Result<Option<Column>, Error> {
+        self.inner
+            .as_ref()
+            .ok_or(Error::Internal("Missing internal connection".to_owned()))?
+            .pluck(statement)
+            .await
+    }
+
+    /// Batch execution
+    async fn batch(&self, statement: Statement) -> Result<(), Error> {
+        self.inner
+            .as_ref()
+            .ok_or(Error::Internal("Missing internal connection".to_owned()))?
+            .batch(statement)
+            .await
+    }
+}
+
+/// Generic transaction handler for SQLite
+pub struct GenericTransactionHandler<W>(PhantomData<W>);
+
+#[async_trait::async_trait]
+impl<W> DatabaseTransaction<W> for GenericTransactionHandler<W>
+where
+    W: DatabaseExecutor,
+{
+    /// Consumes the current transaction committing the changes
+    async fn commit(conn: &mut W) -> Result<(), Error> {
+        query("COMMIT")?.execute(conn).await?;
+        Ok(())
+    }
+
+    /// Begin a transaction
+    async fn begin(conn: &mut W) -> Result<(), Error> {
+        query("BEGIN")?.execute(conn).await?;
+        Ok(())
+    }
+
+    /// Consumes the transaction rolling back all changes
+    async fn rollback(conn: &mut W) -> Result<(), Error> {
+        query("ROLLBACK")?.execute(conn).await?;
+        Ok(())
+    }
 }
 
 /// Database connector
 #[async_trait::async_trait]
 pub trait DatabaseConnector: Debug + DatabaseExecutor + Send + Sync {
-    /// Transaction type for this database connection
-    type Transaction<'a>: DatabaseTransaction<'a>
+    /// Database static trait for the database
+    type Transaction: DatabaseTransaction<Self>
     where
-        Self: 'a;
-
-    /// Begin a new transaction
-    async fn begin(&self) -> Result<Self::Transaction<'_>, Error>;
+        Self: Sized;
 }

crates/cdk-sql-common/src/mint/auth/mod.rs

@@ -1,8 +1,9 @@
 //! SQL Mint Auth
 
 use std::collections::HashMap;
-use std::marker::PhantomData;
+use std::fmt::Debug;
 use std::str::FromStr;
+use std::sync::Arc;
 
 use async_trait::async_trait;
 use cdk_common::database::{self, MintAuthDatabase, MintAuthTransaction};
@@ -15,37 +16,38 @@ use tracing::instrument;
 use super::{sql_row_to_blind_signature, sql_row_to_keyset_info, SQLTransaction};
 use crate::column_as_string;
 use crate::common::migrate;
-use crate::database::{DatabaseConnector, DatabaseTransaction};
+use crate::database::{ConnectionWithTransaction, DatabaseExecutor};
 use crate::mint::Error;
+use crate::pool::{DatabasePool, Pool, PooledResource};
 use crate::stmt::query;
 
 /// Mint SQL Database
 #[derive(Debug, Clone)]
-pub struct SQLMintAuthDatabase<DB>
+pub struct SQLMintAuthDatabase<RM>
 where
-    DB: DatabaseConnector,
+    RM: DatabasePool + 'static,
 {
-    db: DB,
+    pool: Arc<Pool<RM>>,
 }
 
-impl<DB> SQLMintAuthDatabase<DB>
+impl<RM> SQLMintAuthDatabase<RM>
 where
-    DB: DatabaseConnector,
+    RM: DatabasePool + 'static,
 {
     /// Creates a new instance
     pub async fn new<X>(db: X) -> Result<Self, Error>
     where
-        X: Into<DB>,
+        X: Into<RM::Config>,
     {
-        let db = db.into();
-        Self::migrate(&db).await?;
-        Ok(Self { db })
+        let pool = Pool::new(db.into());
+        Self::migrate(pool.get().map_err(|e| Error::Database(Box::new(e)))?).await?;
+        Ok(Self { pool })
     }
 
     /// Migrate
-    async fn migrate(conn: &DB) -> Result<(), Error> {
-        let tx = conn.begin().await?;
-        migrate(&tx, DB::name(), MIGRATIONS).await?;
+    async fn migrate(conn: PooledResource<RM>) -> Result<(), Error> {
+        let tx = ConnectionWithTransaction::new(conn).await?;
+        migrate(&tx, RM::Connection::name(), MIGRATIONS).await?;
         tx.commit().await?;
         Ok(())
     }
@@ -56,9 +58,9 @@ mod migrations;
 
 
 #[async_trait]
-impl<'a, T> MintAuthTransaction<database::Error> for SQLTransaction<'a, T>
+impl<RM> MintAuthTransaction<database::Error> for SQLTransaction<RM>
 where
-    T: DatabaseTransaction<'a>,
+    RM: DatabasePool + 'static,
 {
     #[instrument(skip(self))]
     async fn set_active_keyset(&mut self, id: Id) -> Result<(), database::Error> {
@@ -233,9 +235,9 @@ where
 }
 
 #[async_trait]
-impl<DB> MintAuthDatabase for SQLMintAuthDatabase<DB>
+impl<RM> MintAuthDatabase for SQLMintAuthDatabase<RM>
 where
-    DB: DatabaseConnector,
+    RM: DatabasePool + 'static,
 {
     type Err = database::Error;
 
@@ -244,12 +246,15 @@ where
     ) -> Result<Box<dyn MintAuthTransaction<database::Error> + Send + Sync + 'a>, database::Error>
     {
         Ok(Box::new(SQLTransaction {
-            inner: self.db.begin().await?,
-            _phantom: PhantomData,
+            inner: ConnectionWithTransaction::new(
+                self.pool.get().map_err(|e| Error::Database(Box::new(e)))?,
+            )
+            .await?,
         }))
     }
 
     async fn get_active_keyset_id(&self) -> Result<Option<Id>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -260,13 +265,14 @@ where
                 active = 1;
             "#,
         )?
-        .pluck(&self.db)
+        .pluck(&*conn)
         .await?
         .map(|id| Ok::<_, Error>(column_as_string!(id, Id::from_str, Id::from_bytes)))
         .transpose()?)
     }
 
     async fn get_keyset_info(&self, id: &Id) -> Result<Option<MintKeySetInfo>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"SELECT
                 id,
@@ -283,13 +289,14 @@ where
                 WHERE id=:id"#,
         )?
         .bind("id", id.to_string())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(sql_row_to_keyset_info)
         .transpose()?)
     }
 
     async fn get_keyset_infos(&self) -> Result<Vec<MintKeySetInfo>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"SELECT
                 id,
@@ -305,7 +312,7 @@ where
                 keyset
                 WHERE id=:id"#,
         )?
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(sql_row_to_keyset_info)
@@ -313,9 +320,10 @@ where
     }
 
     async fn get_proofs_states(&self, ys: &[PublicKey]) -> Result<Vec<Option<State>>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         let mut current_states = query(r#"SELECT y, state FROM proof WHERE y IN (:ys)"#)?
             .bind_vec("ys", ys.iter().map(|y| y.to_bytes().to_vec()).collect())
-            .fetch_all(&self.db)
+            .fetch_all(&*conn)
             .await?
             .into_iter()
             .map(|row| {
@@ -333,6 +341,7 @@ where
         &self,
         blinded_messages: &[PublicKey],
     ) -> Result<Vec<Option<BlindSignature>>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         let mut blinded_signatures = query(
             r#"SELECT
                 keyset_id,
@@ -353,7 +362,7 @@ where
                 .map(|y| y.to_bytes().to_vec())
                 .collect(),
         )
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(|mut row| {
@@ -377,10 +386,11 @@ where
         &self,
         protected_endpoint: ProtectedEndpoint,
     ) -> Result<Option<AuthRequired>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(
             query(r#"SELECT auth FROM protected_endpoints WHERE endpoint = :endpoint"#)?
                 .bind("endpoint", serde_json::to_string(&protected_endpoint)?)
-                .pluck(&self.db)
+                .pluck(&*conn)
                 .await?
                 .map(|auth| {
                     Ok::<_, Error>(column_as_string!(
@@ -396,8 +406,9 @@ where
     async fn get_auth_for_endpoints(
         &self,
     ) -> Result<HashMap<ProtectedEndpoint, Option<AuthRequired>>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(r#"SELECT endpoint, auth FROM protected_endpoints"#)?
-            .fetch_all(&self.db)
+            .fetch_all(&*conn)
             .await?
             .into_iter()
             .map(|row| {

crates/cdk-sql-common/src/mint/mod.rs

@@ -9,8 +9,9 @@
 //! clients in a pool and expose them to an asynchronous environment, making them compatible with
 //! Mint.
 use std::collections::HashMap;
-use std::marker::PhantomData;
+use std::fmt::Debug;
 use std::str::FromStr;
+use std::sync::Arc;
 
 use async_trait::async_trait;
 use bitcoin::bip32::DerivationPath;
@@ -38,7 +39,8 @@ use tracing::instrument;
 use uuid::Uuid;
 
 use crate::common::migrate;
-use crate::database::{DatabaseConnector, DatabaseExecutor, DatabaseTransaction};
+use crate::database::{ConnectionWithTransaction, DatabaseExecutor};
+use crate::pool::{DatabasePool, Pool, PooledResource};
 use crate::stmt::{query, Column};
 use crate::{
     column_as_nullable_number, column_as_nullable_string, column_as_number, column_as_string,
@@ -57,20 +59,19 @@ pub use auth::SQLMintAuthDatabase;
 
 /// Mint SQL Database
 #[derive(Debug, Clone)]
-pub struct SQLMintDatabase<DB>
+pub struct SQLMintDatabase<RM>
 where
-    DB: DatabaseConnector,
+    RM: DatabasePool + 'static,
 {
-    db: DB,
+    pool: Arc<Pool<RM>>,
 }
 
 /// SQL Transaction Writer
-pub struct SQLTransaction<'a, T>
+pub struct SQLTransaction<RM>
 where
-    T: DatabaseTransaction<'a>,
+    RM: DatabasePool + 'static,
 {
-    inner: T,
-    _phantom: PhantomData<&'a ()>,
+    inner: ConnectionWithTransaction<RM::Connection, PooledResource<RM>>,
 }
 
 #[inline(always)]
@@ -115,24 +116,26 @@ where
     Ok(())
 }
 
-impl<DB> SQLMintDatabase<DB>
+impl<RM> SQLMintDatabase<RM>
 where
-    DB: DatabaseConnector,
+    RM: DatabasePool + 'static,
 {
     /// Creates a new instance
     pub async fn new<X>(db: X) -> Result<Self, Error>
     where
-        X: Into<DB>,
+        X: Into<RM::Config>,
     {
-        let db = db.into();
-        Self::migrate(&db).await?;
-        Ok(Self { db })
+        let pool = Pool::new(db.into());
+
+        Self::migrate(pool.get().map_err(|e| Error::Database(Box::new(e)))?).await?;
+
+        Ok(Self { pool })
     }
 
     /// Migrate
-    async fn migrate(conn: &DB) -> Result<(), Error> {
-        let tx = conn.begin().await?;
-        migrate(&tx, DB::name(), MIGRATIONS).await?;
+    async fn migrate(conn: PooledResource<RM>) -> Result<(), Error> {
+        let tx = ConnectionWithTransaction::new(conn).await?;
+        migrate(&tx, RM::Connection::name(), MIGRATIONS).await?;
         tx.commit().await?;
         Ok(())
     }
@@ -142,9 +145,10 @@ where
     where
         R: serde::de::DeserializeOwned,
     {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         let value = column_as_string!(query(r#"SELECT value FROM config WHERE id = :id LIMIT 1"#)?
             .bind("id", id.to_owned())
-            .pluck(&self.db)
+            .pluck(&*conn)
             .await?
             .ok_or(Error::UnknownQuoteTTL)?);
 
@@ -153,9 +157,9 @@ where
 }
 
 #[async_trait]
-impl<'a, T> database::MintProofsTransaction<'a> for SQLTransaction<'a, T>
+impl<RM> database::MintProofsTransaction<'_> for SQLTransaction<RM>
 where
-    T: DatabaseTransaction<'a>,
+    RM: DatabasePool + 'static,
 {
     type Err = Error;
 
@@ -267,9 +271,9 @@ where
 }
 
 #[async_trait]
-impl<'a, T> database::MintTransaction<'a, Error> for SQLTransaction<'a, T>
+impl<RM> database::MintTransaction<'_, Error> for SQLTransaction<RM>
 where
-    T: DatabaseTransaction<'a>,
+    RM: DatabasePool + 'static,
 {
     async fn set_mint_info(&mut self, mint_info: MintInfo) -> Result<(), Error> {
         Ok(set_to_config(&self.inner, "mint_info", &mint_info).await?)
@@ -281,18 +285,18 @@ where
 }
 
 #[async_trait]
-impl<'a, T> MintDbWriterFinalizer for SQLTransaction<'a, T>
+impl<RM> MintDbWriterFinalizer for SQLTransaction<RM>
 where
-    T: DatabaseTransaction<'a>,
+    RM: DatabasePool + 'static,
 {
     type Err = Error;
 
     async fn commit(self: Box<Self>) -> Result<(), Error> {
-        Ok(self.inner.commit().await?)
+        self.inner.commit().await
     }
 
     async fn rollback(self: Box<Self>) -> Result<(), Error> {
-        Ok(self.inner.rollback().await?)
+        self.inner.rollback().await
     }
 }
 
@@ -357,9 +361,9 @@ WHERE quote_id=:quote_id
 }
 
 #[async_trait]
-impl<'a, T> MintKeyDatabaseTransaction<'a, Error> for SQLTransaction<'a, T>
+impl<RM> MintKeyDatabaseTransaction<'_, Error> for SQLTransaction<RM>
 where
-    T: DatabaseTransaction<'a>,
+    RM: DatabasePool + 'static,
 {
     async fn add_keyset_info(&mut self, keyset: MintKeySetInfo) -> Result<(), Error> {
         query(
@@ -416,9 +420,9 @@ where
 }
 
 #[async_trait]
-impl<DB> MintKeysDatabase for SQLMintDatabase<DB>
+impl<RM> MintKeysDatabase for SQLMintDatabase<RM>
 where
-    DB: DatabaseConnector,
+    RM: DatabasePool + 'static,
 {
     type Err = Error;
 
@@ -426,16 +430,19 @@ where
         &'a self,
     ) -> Result<Box<dyn MintKeyDatabaseTransaction<'a, Error> + Send + Sync + 'a>, Error> {
         Ok(Box::new(SQLTransaction {
-            inner: self.db.begin().await?,
-            _phantom: PhantomData,
+            inner: ConnectionWithTransaction::new(
+                self.pool.get().map_err(|e| Error::Database(Box::new(e)))?,
+            )
+            .await?,
         }))
     }
 
     async fn get_active_keyset_id(&self, unit: &CurrencyUnit) -> Result<Option<Id>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(
             query(r#" SELECT id FROM keyset WHERE active = 1 AND unit IS :unit"#)?
                 .bind("unit", unit.to_string())
-                .pluck(&self.db)
+                .pluck(&*conn)
                 .await?
                 .map(|id| match id {
                     Column::Text(text) => Ok(Id::from_str(&text)?),
@@ -447,8 +454,9 @@ where
     }
 
     async fn get_active_keysets(&self) -> Result<HashMap<CurrencyUnit, Id>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(r#"SELECT id, unit FROM keyset WHERE active = 1"#)?
-            .fetch_all(&self.db)
+            .fetch_all(&*conn)
             .await?
             .into_iter()
             .map(|row| {
@@ -461,6 +469,7 @@ where
     }
 
     async fn get_keyset_info(&self, id: &Id) -> Result<Option<MintKeySetInfo>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"SELECT
                 id,
@@ -477,13 +486,14 @@ where
                 WHERE id=:id"#,
         )?
         .bind("id", id.to_string())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(sql_row_to_keyset_info)
         .transpose()?)
     }
 
     async fn get_keyset_infos(&self) -> Result<Vec<MintKeySetInfo>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"SELECT
                 id,
@@ -499,7 +509,7 @@ where
                 keyset
             "#,
         )?
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(sql_row_to_keyset_info)
@@ -508,9 +518,9 @@ where
 }
 
 #[async_trait]
-impl<'a, T> MintQuotesTransaction<'a> for SQLTransaction<'a, T>
+impl<RM> MintQuotesTransaction<'_> for SQLTransaction<RM>
 where
-    T: DatabaseTransaction<'a>,
+    RM: DatabasePool + 'static,
 {
     type Err = Error;
 
@@ -1028,15 +1038,17 @@ VALUES (:quote_id, :amount, :timestamp);
 }
 
 #[async_trait]
-impl<DB> MintQuotesDatabase for SQLMintDatabase<DB>
+impl<RM> MintQuotesDatabase for SQLMintDatabase<RM>
 where
-    DB: DatabaseConnector,
+    RM: DatabasePool + 'static,
 {
     type Err = Error;
 
     async fn get_mint_quote(&self, quote_id: &Uuid) -> Result<Option<MintQuote>, Self::Err> {
-        let payments = get_mint_quote_payments(&self.db, quote_id).await?;
-        let issuance = get_mint_quote_issuance(&self.db, quote_id).await?;
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+
+        let payments = get_mint_quote_payments(&*conn, quote_id).await?;
+        let issuance = get_mint_quote_issuance(&*conn, quote_id).await?;
 
         Ok(query(
             r#"
@@ -1058,7 +1070,7 @@ where
             WHERE id = :id"#,
         )?
         .bind("id", quote_id.as_hyphenated().to_string())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(|row| sql_row_to_mint_quote(row, payments, issuance))
         .transpose()?)
@@ -1068,6 +1080,7 @@ where
         &self,
         request: &str,
     ) -> Result<Option<MintQuote>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         let mut mint_quote = query(
             r#"
             SELECT
@@ -1088,14 +1101,14 @@ where
             WHERE request = :request"#,
         )?
         .bind("request", request.to_owned())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(|row| sql_row_to_mint_quote(row, vec![], vec![]))
         .transpose()?;
 
         if let Some(quote) = mint_quote.as_mut() {
-            let payments = get_mint_quote_payments(&self.db, &quote.id).await?;
-            let issuance = get_mint_quote_issuance(&self.db, &quote.id).await?;
+            let payments = get_mint_quote_payments(&*conn, &quote.id).await?;
+            let issuance = get_mint_quote_issuance(&*conn, &quote.id).await?;
             quote.issuance = issuance;
             quote.payments = payments;
         }
@@ -1107,6 +1120,7 @@ where
         &self,
         request_lookup_id: &PaymentIdentifier,
     ) -> Result<Option<MintQuote>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         let mut mint_quote = query(
             r#"
             SELECT
@@ -1130,15 +1144,15 @@ where
         )?
         .bind("request_lookup_id", request_lookup_id.to_string())
         .bind("request_lookup_id_kind", request_lookup_id.kind())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(|row| sql_row_to_mint_quote(row, vec![], vec![]))
         .transpose()?;
 
         // TODO: these should use an sql join so they can be done in one query
         if let Some(quote) = mint_quote.as_mut() {
-            let payments = get_mint_quote_payments(&self.db, &quote.id).await?;
-            let issuance = get_mint_quote_issuance(&self.db, &quote.id).await?;
+            let payments = get_mint_quote_payments(&*conn, &quote.id).await?;
+            let issuance = get_mint_quote_issuance(&*conn, &quote.id).await?;
             quote.issuance = issuance;
             quote.payments = payments;
         }
@@ -1147,6 +1161,7 @@ where
     }
 
     async fn get_mint_quotes(&self) -> Result<Vec<MintQuote>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         let mut mint_quotes = query(
             r#"
             SELECT
@@ -1166,15 +1181,15 @@ where
                 mint_quote
             "#,
         )?
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(|row| sql_row_to_mint_quote(row, vec![], vec![]))
         .collect::<Result<Vec<_>, _>>()?;
 
         for quote in mint_quotes.as_mut_slice() {
-            let payments = get_mint_quote_payments(&self.db, &quote.id).await?;
-            let issuance = get_mint_quote_issuance(&self.db, &quote.id).await?;
+            let payments = get_mint_quote_payments(&*conn, &quote.id).await?;
+            let issuance = get_mint_quote_issuance(&*conn, &quote.id).await?;
             quote.issuance = issuance;
             quote.payments = payments;
         }
@@ -1183,6 +1198,7 @@ where
     }
 
     async fn get_melt_quote(&self, quote_id: &Uuid) -> Result<Option<mint::MeltQuote>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -1207,13 +1223,14 @@ where
             "#,
         )?
         .bind("id", quote_id.as_hyphenated().to_string())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(sql_row_to_melt_quote)
         .transpose()?)
     }
 
     async fn get_melt_quotes(&self) -> Result<Vec<mint::MeltQuote>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -1235,7 +1252,7 @@ where
                 melt_quote
             "#,
         )?
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(sql_row_to_melt_quote)
@@ -1244,13 +1261,14 @@ where
 }
 
 #[async_trait]
-impl<DB> MintProofsDatabase for SQLMintDatabase<DB>
+impl<RM> MintProofsDatabase for SQLMintDatabase<RM>
 where
-    DB: DatabaseConnector,
+    RM: DatabasePool + 'static,
 {
     type Err = Error;
 
     async fn get_proofs_by_ys(&self, ys: &[PublicKey]) -> Result<Vec<Option<Proof>>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         let mut proofs = query(
             r#"
             SELECT
@@ -1267,7 +1285,7 @@ where
             "#,
         )?
         .bind_vec("ys", ys.iter().map(|y| y.to_bytes().to_vec()).collect())
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(|mut row| {
@@ -1286,6 +1304,7 @@ where
     }
 
     async fn get_proof_ys_by_quote_id(&self, quote_id: &Uuid) -> Result<Vec<PublicKey>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -1301,7 +1320,7 @@ where
             "#,
         )?
         .bind("quote_id", quote_id.as_hyphenated().to_string())
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(sql_row_to_proof)
@@ -1310,7 +1329,8 @@ where
     }
 
     async fn get_proofs_states(&self, ys: &[PublicKey]) -> Result<Vec<Option<State>>, Self::Err> {
-        let mut current_states = get_current_states(&self.db, ys).await?;
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+        let mut current_states = get_current_states(&*conn, ys).await?;
 
         Ok(ys.iter().map(|y| current_states.remove(y)).collect())
     }
@@ -1319,6 +1339,7 @@ where
         &self,
         keyset_id: &Id,
     ) -> Result<(Proofs, Vec<Option<State>>), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -1335,7 +1356,7 @@ where
             "#,
         )?
         .bind("keyset_id", keyset_id.to_string())
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(sql_row_to_proof_with_state)
@@ -1346,9 +1367,9 @@ where
 }
 
 #[async_trait]
-impl<'a, T> MintSignatureTransaction<'a> for SQLTransaction<'a, T>
+impl<RM> MintSignatureTransaction<'_> for SQLTransaction<RM>
 where
-    T: DatabaseTransaction<'a>,
+    RM: DatabasePool + 'static,
 {
     type Err = Error;
 
@@ -1436,9 +1457,9 @@ where
 }
 
 #[async_trait]
-impl<DB> MintSignaturesDatabase for SQLMintDatabase<DB>
+impl<RM> MintSignaturesDatabase for SQLMintDatabase<RM>
 where
-    DB: DatabaseConnector,
+    RM: DatabasePool + 'static,
 {
     type Err = Error;
 
@@ -1446,6 +1467,7 @@ where
         &self,
         blinded_messages: &[PublicKey],
     ) -> Result<Vec<Option<BlindSignature>>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         let mut blinded_signatures = query(
             r#"SELECT
                 keyset_id,
@@ -1466,7 +1488,7 @@ where
                 .map(|b_| b_.to_bytes().to_vec())
                 .collect(),
         )
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(|mut row| {
@@ -1490,6 +1512,7 @@ where
         &self,
         keyset_id: &Id,
     ) -> Result<Vec<BlindSignature>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -1505,7 +1528,7 @@ where
             "#,
         )?
         .bind("keyset_id", keyset_id.to_string())
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(sql_row_to_blind_signature)
@@ -1517,6 +1540,7 @@ where
         &self,
         quote_id: &Uuid,
     ) -> Result<Vec<BlindSignature>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -1532,7 +1556,7 @@ where
             "#,
         )?
         .bind("quote_id", quote_id.to_string())
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(sql_row_to_blind_signature)
@@ -1541,16 +1565,18 @@ where
 }
 
 #[async_trait]
-impl<DB> MintDatabase<Error> for SQLMintDatabase<DB>
+impl<RM> MintDatabase<Error> for SQLMintDatabase<RM>
 where
-    DB: DatabaseConnector,
+    RM: DatabasePool + 'static,
 {
     async fn begin_transaction<'a>(
         &'a self,
     ) -> Result<Box<dyn database::MintTransaction<'a, Error> + Send + Sync + 'a>, Error> {
         Ok(Box::new(SQLTransaction {
-            inner: self.db.begin().await?,
-            _phantom: PhantomData,
+            inner: ConnectionWithTransaction::new(
+                self.pool.get().map_err(|e| Error::Database(Box::new(e)))?,
+            )
+            .await?,
         }))
     }
 

crates/cdk-sql-common/src/pool.rs

@@ -8,9 +8,14 @@ use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 use std::sync::{Arc, Condvar, Mutex};
 use std::time::Duration;
 
+use crate::database::DatabaseConnector;
+
 /// Pool error
-#[derive(thiserror::Error, Debug)]
-pub enum Error<E> {
+#[derive(Debug, thiserror::Error)]
+pub enum Error<E>
+where
+    E: std::error::Error + Send + Sync + 'static,
+{
     /// Mutex Poison Error
     #[error("Internal: PoisonError")]
     Poison,
@@ -24,16 +29,25 @@ pub enum Error<E> {
     Resource(#[from] E),
 }
 
+/// Configuration
+pub trait DatabaseConfig: Clone + Debug + Send + Sync {
+    /// Max resource sizes
+    fn max_size(&self) -> usize;
+
+    /// Default timeout
+    fn default_timeout(&self) -> Duration;
+}
+
 /// Trait to manage resources
-pub trait ResourceManager: Debug {
+pub trait DatabasePool: Debug {
     /// The resource to be pooled
-    type Resource: Debug;
+    type Connection: DatabaseConnector;
 
     /// The configuration that is needed in order to create the resource
-    type Config: Clone + Debug;
+    type Config: DatabaseConfig;
 
     /// The error the resource may return when creating a new instance
-    type Error: Debug;
+    type Error: Debug + std::error::Error + Send + Sync + 'static;
 
     /// Creates a new resource with a given config.
     ///
@@ -43,20 +57,20 @@ pub trait ResourceManager: Debug {
         config: &Self::Config,
         stale: Arc<AtomicBool>,
         timeout: Duration,
-    ) -> Result<Self::Resource, Error<Self::Error>>;
+    ) -> Result<Self::Connection, Error<Self::Error>>;
 
     /// The object is dropped
-    fn drop(_resource: Self::Resource) {}
+    fn drop(_resource: Self::Connection) {}
 }
 
 /// Generic connection pool of resources R
 #[derive(Debug)]
 pub struct Pool<RM>
 where
-    RM: ResourceManager,
+    RM: DatabasePool,
 {
     config: RM::Config,
-    queue: Mutex<Vec<(Arc<AtomicBool>, RM::Resource)>>,
+    queue: Mutex<Vec<(Arc<AtomicBool>, RM::Connection)>>,
     in_use: AtomicUsize,
     max_size: usize,
     default_timeout: Duration,
@@ -66,15 +80,24 @@ where
 /// The pooled resource
 pub struct PooledResource<RM>
 where
-    RM: ResourceManager,
+    RM: DatabasePool,
 {
-    resource: Option<(Arc<AtomicBool>, RM::Resource)>,
+    resource: Option<(Arc<AtomicBool>, RM::Connection)>,
     pool: Arc<Pool<RM>>,
 }
 
+impl<RM> Debug for PooledResource<RM>
+where
+    RM: DatabasePool,
+{
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Resource: {:?}", self.resource)
+    }
+}
+
 impl<RM> Drop for PooledResource<RM>
 where
-    RM: ResourceManager,
+    RM: DatabasePool,
 {
     fn drop(&mut self) {
         if let Some(resource) = self.resource.take() {
@@ -90,9 +113,9 @@ where
 
 impl<RM> Deref for PooledResource<RM>
 where
-    RM: ResourceManager,
+    RM: DatabasePool,
 {
-    type Target = RM::Resource;
+    type Target = RM::Connection;
 
     fn deref(&self) -> &Self::Target {
         &self.resource.as_ref().expect("resource already dropped").1
@@ -101,7 +124,7 @@ where
 
 impl<RM> DerefMut for PooledResource<RM>
 where
-    RM: ResourceManager,
+    RM: DatabasePool,
 {
     fn deref_mut(&mut self) -> &mut Self::Target {
         &mut self.resource.as_mut().expect("resource already dropped").1
@@ -110,17 +133,17 @@ where
 
 impl<RM> Pool<RM>
 where
-    RM: ResourceManager,
+    RM: DatabasePool,
 {
     /// Creates a new pool
-    pub fn new(config: RM::Config, max_size: usize, default_timeout: Duration) -> Arc<Self> {
+    pub fn new(config: RM::Config) -> Arc<Self> {
         Arc::new(Self {
+            default_timeout: config.default_timeout(),
+            max_size: config.max_size(),
             config,
             queue: Default::default(),
             in_use: Default::default(),
             waiter: Default::default(),
-            default_timeout,
-            max_size,
         })
     }
 
@@ -185,7 +208,7 @@ where
 
 impl<RM> Drop for Pool<RM>
 where
-    RM: ResourceManager,
+    RM: DatabasePool,
 {
     fn drop(&mut self) {
         if let Ok(mut resources) = self.queue.lock() {

crates/cdk-sql-common/src/wallet/mod.rs

@@ -1,7 +1,9 @@
 //! SQLite Wallet Database
 
 use std::collections::HashMap;
+use std::fmt::Debug;
 use std::str::FromStr;
+use std::sync::Arc;
 
 use async_trait::async_trait;
 use cdk_common::common::ProofInfo;
@@ -17,7 +19,8 @@ use cdk_common::{
 use tracing::instrument;
 
 use crate::common::migrate;
-use crate::database::DatabaseExecutor;
+use crate::database::{ConnectionWithTransaction, DatabaseExecutor};
+use crate::pool::{DatabasePool, Pool, PooledResource};
 use crate::stmt::{query, Column};
 use crate::{
     column_as_binary, column_as_nullable_binary, column_as_nullable_number,
@@ -29,36 +32,43 @@ mod migrations;
 
 /// Wallet SQLite Database
 #[derive(Debug, Clone)]
-pub struct SQLWalletDatabase<T>
+pub struct SQLWalletDatabase<RM>
 where
-    T: DatabaseExecutor,
+    RM: DatabasePool + 'static,
 {
-    db: T,
+    pool: Arc<Pool<RM>>,
 }
 
-impl<DB> SQLWalletDatabase<DB>
+impl<RM> SQLWalletDatabase<RM>
 where
-    DB: DatabaseExecutor,
+    RM: DatabasePool + 'static,
 {
     /// Creates a new instance
     pub async fn new<X>(db: X) -> Result<Self, Error>
     where
-        X: Into<DB>,
+        X: Into<RM::Config>,
     {
-        let db = db.into();
-        Self::migrate(&db).await?;
-        Ok(Self { db })
+        let pool = Pool::new(db.into());
+        Self::migrate(pool.get().map_err(|e| Error::Database(Box::new(e)))?).await?;
+
+        Ok(Self { pool })
     }
 
     /// Migrate [`WalletSqliteDatabase`]
-    async fn migrate(conn: &DB) -> Result<(), Error> {
-        migrate(conn, DB::name(), migrations::MIGRATIONS).await?;
+    async fn migrate(conn: PooledResource<RM>) -> Result<(), Error> {
+        let tx = ConnectionWithTransaction::new(conn).await?;
+        migrate(&tx, RM::Connection::name(), migrations::MIGRATIONS).await?;
         // Update any existing keys with missing keyset_u32 values
-        Self::add_keyset_u32(conn).await?;
+        Self::add_keyset_u32(&tx).await?;
+        tx.commit().await?;
+
         Ok(())
     }
 
-    async fn add_keyset_u32(conn: &DB) -> Result<(), Error> {
+    async fn add_keyset_u32<T>(conn: &T) -> Result<(), Error>
+    where
+        T: DatabaseExecutor,
+    {
         // First get the keysets where keyset_u32 on key is null
         let keys_without_u32: Vec<Vec<Column>> = query(
             r#"
@@ -126,14 +136,16 @@ where
 }
 
 #[async_trait]
-impl<T> WalletDatabase for SQLWalletDatabase<T>
+impl<RM> WalletDatabase for SQLWalletDatabase<RM>
 where
-    T: DatabaseExecutor,
+    RM: DatabasePool + 'static,
 {
     type Err = database::Error;
 
     #[instrument(skip(self))]
     async fn get_melt_quotes(&self) -> Result<Vec<wallet::MeltQuote>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+
         Ok(query(
             r#"
               SELECT
@@ -149,7 +161,7 @@ where
                   melt_quote
               "#,
         )?
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(sql_row_to_melt_quote)
@@ -212,6 +224,8 @@ where
             ),
         };
 
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+
         query(
             r#"
 INSERT INTO mint
@@ -253,7 +267,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
         .bind("motd", motd)
         .bind("mint_time", time.map(|v| v as i64))
         .bind("tos_url", tos_url)
-        .execute(&self.db)
+        .execute(&*conn)
         .await?;
 
         Ok(())
@@ -261,9 +275,11 @@ ON CONFLICT(mint_url) DO UPDATE SET
 
     #[instrument(skip(self))]
     async fn remove_mint(&self, mint_url: MintUrl) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+
         query(r#"DELETE FROM mint WHERE mint_url=:mint_url"#)?
             .bind("mint_url", mint_url.to_string())
-            .execute(&self.db)
+            .execute(&*conn)
             .await?;
 
         Ok(())
@@ -271,6 +287,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
 
     #[instrument(skip(self))]
     async fn get_mint(&self, mint_url: MintUrl) -> Result<Option<MintInfo>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -292,7 +309,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
             "#,
         )?
         .bind("mint_url", mint_url.to_string())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(sql_row_to_mint_info)
         .transpose()?)
@@ -300,6 +317,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
 
     #[instrument(skip(self))]
     async fn get_mints(&self) -> Result<HashMap<MintUrl, Option<MintInfo>>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
                 SELECT
@@ -320,7 +338,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
                     mint
                 "#,
         )?
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(|mut row| {
@@ -340,6 +358,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
         old_mint_url: MintUrl,
         new_mint_url: MintUrl,
     ) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         let tables = ["mint_quote", "proof"];
 
         for table in &tables {
@@ -352,7 +371,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
             ))?
             .bind("new_mint_url", new_mint_url.to_string())
             .bind("old_mint_url", old_mint_url.to_string())
-            .execute(&self.db)
+            .execute(&*conn)
             .await?;
         }
 
@@ -365,6 +384,8 @@ ON CONFLICT(mint_url) DO UPDATE SET
         mint_url: MintUrl,
         keysets: Vec<KeySetInfo>,
     ) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+
         for keyset in keysets {
             query(
                 r#"
@@ -384,7 +405,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
             .bind("input_fee_ppk", keyset.input_fee_ppk as i64)
             .bind("final_expiry", keyset.final_expiry.map(|v| v as i64))
             .bind("keyset_u32", u32::from(keyset.id))
-            .execute(&self.db)
+            .execute(&*conn)
             .await?;
         }
 
@@ -396,6 +417,8 @@ ON CONFLICT(mint_url) DO UPDATE SET
         &self,
         mint_url: MintUrl,
     ) -> Result<Option<Vec<KeySetInfo>>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+
         let keysets = query(
             r#"
             SELECT
@@ -410,7 +433,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
             "#,
         )?
         .bind("mint_url", mint_url.to_string())
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(sql_row_to_keyset)
@@ -424,6 +447,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
 
     #[instrument(skip(self), fields(keyset_id = %keyset_id))]
     async fn get_keyset_by_id(&self, keyset_id: &Id) -> Result<Option<KeySetInfo>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -438,7 +462,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
             "#,
         )?
         .bind("id", keyset_id.to_string())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(sql_row_to_keyset)
         .transpose()?)
@@ -446,6 +470,7 @@ ON CONFLICT(mint_url) DO UPDATE SET
 
     #[instrument(skip_all)]
     async fn add_mint_quote(&self, quote: MintQuote) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         query(
             r#"
 INSERT INTO mint_quote
@@ -477,13 +502,14 @@ ON CONFLICT(id) DO UPDATE SET
         .bind("payment_method", quote.payment_method.to_string())
         .bind("amount_issued", quote.amount_issued.to_i64())
         .bind("amount_paid", quote.amount_paid.to_i64())
-        .execute(&self.db).await?;
+        .execute(&*conn).await?;
 
         Ok(())
     }
 
     #[instrument(skip(self))]
     async fn get_mint_quote(&self, quote_id: &str) -> Result<Option<MintQuote>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -505,7 +531,7 @@ ON CONFLICT(id) DO UPDATE SET
             "#,
         )?
         .bind("id", quote_id.to_string())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(sql_row_to_mint_quote)
         .transpose()?)
@@ -513,6 +539,7 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip(self))]
     async fn get_mint_quotes(&self) -> Result<Vec<MintQuote>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -528,7 +555,7 @@ ON CONFLICT(id) DO UPDATE SET
                 mint_quote
             "#,
         )?
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .map(sql_row_to_mint_quote)
@@ -537,9 +564,10 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip(self))]
     async fn remove_mint_quote(&self, quote_id: &str) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         query(r#"DELETE FROM mint_quote WHERE id=:id"#)?
             .bind("id", quote_id.to_string())
-            .execute(&self.db)
+            .execute(&*conn)
             .await?;
 
         Ok(())
@@ -547,6 +575,7 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip_all)]
     async fn add_melt_quote(&self, quote: wallet::MeltQuote) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         query(
             r#"
 INSERT INTO melt_quote
@@ -570,7 +599,7 @@ ON CONFLICT(id) DO UPDATE SET
         .bind("fee_reserve", u64::from(quote.fee_reserve) as i64)
         .bind("state", quote.state.to_string())
         .bind("expiry", quote.expiry as i64)
-        .execute(&self.db)
+        .execute(&*conn)
         .await?;
 
         Ok(())
@@ -578,6 +607,7 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip(self))]
     async fn get_melt_quote(&self, quote_id: &str) -> Result<Option<wallet::MeltQuote>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -596,7 +626,7 @@ ON CONFLICT(id) DO UPDATE SET
             "#,
         )?
         .bind("id", quote_id.to_owned())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(sql_row_to_melt_quote)
         .transpose()?)
@@ -604,9 +634,10 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip(self))]
     async fn remove_melt_quote(&self, quote_id: &str) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         query(r#"DELETE FROM melt_quote WHERE id=:id"#)?
             .bind("id", quote_id.to_owned())
-            .execute(&self.db)
+            .execute(&*conn)
             .await?;
 
         Ok(())
@@ -614,6 +645,8 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip_all)]
     async fn add_keys(&self, keyset: KeySet) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+
         // Recompute ID for verification
         keyset.verify_id()?;
 
@@ -631,7 +664,7 @@ ON CONFLICT(id) DO UPDATE SET
             serde_json::to_string(&keyset.keys).map_err(Error::from)?,
         )
         .bind("keyset_u32", u32::from(keyset.id))
-        .execute(&self.db)
+        .execute(&*conn)
         .await?;
 
         Ok(())
@@ -639,6 +672,7 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip(self), fields(keyset_id = %keyset_id))]
     async fn get_keys(&self, keyset_id: &Id) -> Result<Option<Keys>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -648,7 +682,7 @@ ON CONFLICT(id) DO UPDATE SET
             "#,
         )?
         .bind("id", keyset_id.to_string())
-        .pluck(&self.db)
+        .pluck(&*conn)
         .await?
         .map(|keys| {
             let keys = column_as_string!(keys);
@@ -659,9 +693,10 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip(self))]
     async fn remove_keys(&self, id: &Id) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         query(r#"DELETE FROM key WHERE id = :id"#)?
             .bind("id", id.to_string())
-            .pluck(&self.db)
+            .pluck(&*conn)
             .await?;
 
         Ok(())
@@ -672,6 +707,10 @@ ON CONFLICT(id) DO UPDATE SET
         added: Vec<ProofInfo>,
         removed_ys: Vec<PublicKey>,
     ) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+
+        let tx = ConnectionWithTransaction::new(conn).await?;
+
         // TODO: Use a transaction for all these operations
         for proof in added {
             query(
@@ -729,7 +768,7 @@ ON CONFLICT(id) DO UPDATE SET
                 "dleq_r",
                 proof.proof.dleq.as_ref().map(|dleq| dleq.r.to_secret_bytes().to_vec()),
             )
-            .execute(&self.db).await?;
+            .execute(&tx).await?;
         }
 
         query(r#"DELETE FROM proof WHERE y IN (:ys)"#)?
@@ -737,9 +776,11 @@ ON CONFLICT(id) DO UPDATE SET
                 "ys",
                 removed_ys.iter().map(|y| y.to_bytes().to_vec()).collect(),
             )
-            .execute(&self.db)
+            .execute(&tx)
             .await?;
 
+        tx.commit().await?;
+
         Ok(())
     }
 
@@ -751,6 +792,7 @@ ON CONFLICT(id) DO UPDATE SET
         state: Option<Vec<State>>,
         spending_conditions: Option<Vec<SpendingConditions>>,
     ) -> Result<Vec<ProofInfo>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -770,7 +812,7 @@ ON CONFLICT(id) DO UPDATE SET
             FROM proof
         "#,
         )?
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .filter_map(|row| {
@@ -786,10 +828,11 @@ ON CONFLICT(id) DO UPDATE SET
     }
 
     async fn update_proofs_state(&self, ys: Vec<PublicKey>, state: State) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         query("UPDATE proof SET state = :state WHERE y IN (:ys)")?
             .bind_vec("ys", ys.iter().map(|y| y.to_bytes().to_vec()).collect())
             .bind("state", state.to_string())
-            .execute(&self.db)
+            .execute(&*conn)
             .await?;
 
         Ok(())
@@ -797,6 +840,7 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip(self), fields(keyset_id = %keyset_id))]
     async fn increment_keyset_counter(&self, keyset_id: &Id, count: u32) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         query(
             r#"
             UPDATE keyset
@@ -806,7 +850,7 @@ ON CONFLICT(id) DO UPDATE SET
         )?
         .bind("count", count)
         .bind("id", keyset_id.to_string())
-        .execute(&self.db)
+        .execute(&*conn)
         .await?;
 
         Ok(())
@@ -814,6 +858,7 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip(self), fields(keyset_id = %keyset_id))]
     async fn get_keyset_counter(&self, keyset_id: &Id) -> Result<Option<u32>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -825,7 +870,7 @@ ON CONFLICT(id) DO UPDATE SET
             "#,
         )?
         .bind("id", keyset_id.to_string())
-        .pluck(&self.db)
+        .pluck(&*conn)
         .await?
         .map(|n| Ok::<_, Error>(column_as_number!(n)))
         .transpose()?)
@@ -833,6 +878,7 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip(self))]
     async fn add_transaction(&self, transaction: Transaction) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         let mint_url = transaction.mint_url.to_string();
         let direction = transaction.direction.to_string();
         let unit = transaction.unit.to_string();
@@ -876,7 +922,7 @@ ON CONFLICT(id) DO UPDATE SET
             "metadata",
             serde_json::to_string(&transaction.metadata).map_err(Error::from)?,
         )
-        .execute(&self.db)
+        .execute(&*conn)
         .await?;
 
         Ok(())
@@ -887,6 +933,7 @@ ON CONFLICT(id) DO UPDATE SET
         &self,
         transaction_id: TransactionId,
     ) -> Result<Option<Transaction>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
         Ok(query(
             r#"
             SELECT
@@ -906,7 +953,7 @@ ON CONFLICT(id) DO UPDATE SET
             "#,
         )?
         .bind("id", transaction_id.as_slice().to_vec())
-        .fetch_one(&self.db)
+        .fetch_one(&*conn)
         .await?
         .map(sql_row_to_transaction)
         .transpose()?)
@@ -919,6 +966,8 @@ ON CONFLICT(id) DO UPDATE SET
         direction: Option<TransactionDirection>,
         unit: Option<CurrencyUnit>,
     ) -> Result<Vec<Transaction>, Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+
         Ok(query(
             r#"
             SELECT
@@ -935,7 +984,7 @@ ON CONFLICT(id) DO UPDATE SET
                 transactions
             "#,
         )?
-        .fetch_all(&self.db)
+        .fetch_all(&*conn)
         .await?
         .into_iter()
         .filter_map(|row| {
@@ -952,9 +1001,11 @@ ON CONFLICT(id) DO UPDATE SET
 
     #[instrument(skip(self))]
     async fn remove_transaction(&self, transaction_id: TransactionId) -> Result<(), Self::Err> {
+        let conn = self.pool.get().map_err(|e| Error::Database(Box::new(e)))?;
+
         query(r#"DELETE FROM transactions WHERE id=:id"#)?
             .bind("id", transaction_id.as_slice().to_vec())
-            .execute(&self.db)
+            .execute(&*conn)
             .await?;
 
         Ok(())