How Can I Safely Determine the Status of a database/sql Transaction Without Errors?

database/sql Tx: Detecting Transaction Status

Question:

How can you determine whether a transaction using database/sql has been committed or rolled back without triggering an error?

Answer:

To detect the transaction status, adhere to the following best practices:

1. Keep Transactions within Functions:

Ensure that Begin(), Commit(), and Rollback() are called within the same function. This ensures that transactions are tracked seamlessly.

2. Utilize Defer for Transaction Closure:

Incorporate a defer function to perform a Rollback if necessary. This guarantees proper transaction handling.

3. Transaction Handler for Succinctness:

Implement a transaction handler function to encapsulate transactions, ensuring brevity and proper handling.

Code Example:

import "database/sql"

func Transact(db *sql.DB, txFunc func(*sql.Tx) error) (err error) {
    tx, err := db.Begin()
    if err != nil {
        return
    }
    defer func() {
        if p := recover(); p != nil {
            tx.Rollback()
            panic(p)
        } else if err != nil {
            tx.Rollback()
        } else {
            err = tx.Commit()
        }
    }()
    err = txFunc(tx)
    return err
}

Using the transaction handler:

func (s Service) DoSomething() error {
    return Transact(s.db, func(tx *sql.Tx) error {
        if _, err := tx.Exec(...); err != nil {
            return err
        }
        if _, err := tx.Exec(...); err != nil {
            return err
        }
        return nil
    })
}

Handling Panics:

Utilize recover() to capture panics and ensure a timely Rollback. Re-throw the panic to allow handling if it is expected.

GC and Tx Object:

Setting Tx to nil after Commit or Rollback does not automatically free up memory. Instead, rely on the garbage collector to handle this.

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