Function with_nested_transaction 

pub async fn with_nested_transaction<F, T>(
    tx_ctx: &mut TransactionContext<'_>,
    f: F,
) -> Result<T>
where
    F: for<'a> FnOnce(&'a mut TransactionContext<'_>) -> Pin<Box<dyn Future<Output = Result<T>> + Send + 'a>>,
    T: Send,

Executes a nested transaction using savepoints.

This function allows you to create a transaction within an existing transaction by using MySQL savepoints. If the nested transaction fails, only operations since the savepoint are rolled back.

Type Parameters

• F - A function that takes a mutable TransactionContext and returns a future
• Fut - The future type returned by the function
• T - The return type (must be Send)

Arguments

• tx_ctx - The existing transaction context
• f - The function to execute within the nested transaction

Returns

Returns the result of the function execution, or an error if the savepoint operation fails.

Examples

use sqlx::MySqlPool;
use sqlx_transaction_manager::{with_transaction, with_nested_transaction};

with_transaction(&pool, |tx| {
    Box::pin(async move {
        // Outer transaction operations
        sqlx::query("INSERT INTO users (name) VALUES (?)")
            .bind("Alice")
            .execute(tx.as_executor())
            .await?;

        // Nested transaction with savepoint
        let nested_result = with_nested_transaction(tx, |nested_tx| {
            Box::pin(async move {
                sqlx::query("INSERT INTO logs (message) VALUES (?)")
                    .bind("User created")
                    .execute(nested_tx.as_executor())
                    .await?;
                Ok::<_, sqlx::Error>(())
            })
        }).await;

        // If nested transaction fails, outer transaction can still succeed
        if nested_result.is_err() {
            println!("Logging failed, but user creation will still commit");
        }

        Ok::<_, sqlx::Error>(())
    })
}).await?;

Note

MySQL doesn’t support true nested transactions. This function uses SAVEPOINTs to simulate nested transaction behavior. The savepoint name is nested_tx.