Add SQLite transaction modes

Author: raffomania

src/database/connection.rs

@@ -125,6 +125,45 @@ impl std::fmt::Display for AccessMode {
     }
 }
 
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+/// Which kind of transaction to start. Only supported by SQLite.
+/// <https://www.sqlite.org/lang_transaction.html>
+#[cfg(feature = "sqlx-sqlite")]
+pub enum SqliteTransactionMode {
+    /// The default. Transaction starts when the next statement is executed, and
+    /// will be a read or write transaction depending on that statement.
+    Deferred,
+    /// Start a write transaction as soon as the BEGIN statement is received.
+    Immediate,
+    /// Start a write transaction as soon as the BEGIN statement is received.
+    /// When in non-WAL mode, also block all other transactions from reading the
+    /// database.
+    Exclusive,
+}
+
+#[cfg(feature = "sqlx-sqlite")]
+impl SqliteTransactionMode {
+    /// The keyword used to start a transaction in this mode (the word coming after "BEGIN").
+    pub fn sqlite_keyword(&self) -> &'static str {
+        match self {
+            SqliteTransactionMode::Deferred => "DEFERRED",
+            SqliteTransactionMode::Immediate => "IMMEDIATE",
+            SqliteTransactionMode::Exclusive => "EXCLUSIVE",
+        }
+    }
+}
+
+/// Configuration for starting a transaction
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Default)]
+pub struct TransactionConfig {
+    #[cfg(any(feature = "sqlx-postgres", feature = "sqlx-mysql"))]
+    pub isolation_level: Option<IsolationLevel>,
+    #[cfg(any(feature = "sqlx-postgres", feature = "sqlx-mysql"))]
+    pub access_mode: Option<AccessMode>,
+    #[cfg(feature = "sqlx-sqlite")]
+    pub sqlite_transaction_mode: Option<SqliteTransactionMode>,
+}
+
 /// Spawn database transaction
 #[async_trait::async_trait]
 pub trait TransactionTrait {

src/database/transaction.rs

@@ -1,8 +1,8 @@
 #![allow(unused_assignments)]
 use crate::{
     AccessMode, ConnectionTrait, DbBackend, DbErr, ExecResult, InnerConnection, IsolationLevel,
-    QueryResult, Statement, StreamTrait, TransactionSession, TransactionStream, TransactionTrait,
-    debug_print, error::*,
+    QueryResult, SqliteTransactionMode, Statement, StreamTrait, TransactionSession,
+    TransactionStream, TransactionTrait, debug_print, error::*,
 };
 #[cfg(feature = "sqlx-dep")]
 use crate::{sqlx_error_to_exec_err, sqlx_error_to_query_err};
@@ -92,7 +92,12 @@ impl DatabaseTransaction {
                             access_mode,
                         )
                         .await?;
-                        <sqlx::Sqlite as sqlx::Database>::TransactionManager::begin(c, None)
+                        // TODO using this for beginning a nested transaction currently causes an error. Should we make it a warning instead?
+                        let statement = match config.sqlite_transaction_mode {
+                            Some(mode) => Some(format!("BEGIN {}", mode.sqlite_keyword())),
+                            None => None,
+                        };
+                        <sqlx::Sqlite as sqlx::Database>::TransactionManager::begin(c, statement)
                             .await
                             .map_err(sqlx_error_to_query_err)
                     }