package pgx import ( "context" "errors" "fmt" "strconv" "strings" "github.com/jackc/pgx/v5/pgconn" ) // TxIsoLevel is the transaction isolation level (serializable, repeatable read, read committed or read uncommitted) type TxIsoLevel string // Transaction isolation levels const ( Serializable TxIsoLevel = "serializable" RepeatableRead TxIsoLevel = "repeatable read" ReadCommitted TxIsoLevel = "read committed" ReadUncommitted TxIsoLevel = "read uncommitted" ) // TxAccessMode is the transaction access mode (read write or read only) type TxAccessMode string // Transaction access modes const ( ReadWrite TxAccessMode = "read write" ReadOnly TxAccessMode = "read only" ) // TxDeferrableMode is the transaction deferrable mode (deferrable or not deferrable) type TxDeferrableMode string // Transaction deferrable modes const ( Deferrable TxDeferrableMode = "deferrable" NotDeferrable TxDeferrableMode = "not deferrable" ) // TxOptions are transaction modes within a transaction block type TxOptions struct { IsoLevel TxIsoLevel AccessMode TxAccessMode DeferrableMode TxDeferrableMode // BeginQuery is the SQL query that will be executed to begin the transaction. This allows using non-standard syntax // such as BEGIN PRIORITY HIGH with CockroachDB. If set this will override the other settings. BeginQuery string } var emptyTxOptions TxOptions func (txOptions TxOptions) beginSQL() string { if txOptions == emptyTxOptions { return "begin" } if txOptions.BeginQuery != "" { return txOptions.BeginQuery } var buf strings.Builder buf.Grow(64) // 64 - maximum length of string with available options buf.WriteString("begin") if txOptions.IsoLevel != "" { buf.WriteString(" isolation level ") buf.WriteString(string(txOptions.IsoLevel)) } if txOptions.AccessMode != "" { buf.WriteByte(' ') buf.WriteString(string(txOptions.AccessMode)) } if txOptions.DeferrableMode != "" { buf.WriteByte(' ') buf.WriteString(string(txOptions.DeferrableMode)) } return buf.String() } var ErrTxClosed = errors.New("tx is closed") // ErrTxCommitRollback occurs when an error has occurred in a transaction and // Commit() is called. PostgreSQL accepts COMMIT on aborted transactions, but // it is treated as ROLLBACK. var ErrTxCommitRollback = errors.New("commit unexpectedly resulted in rollback") // Begin starts a transaction. Unlike database/sql, the context only affects the begin command. i.e. there is no // auto-rollback on context cancellation. func (c *Conn) Begin(ctx context.Context) (Tx, error) { return c.BeginTx(ctx, TxOptions{}) } // BeginTx starts a transaction with txOptions determining the transaction mode. Unlike database/sql, the context only // affects the begin command. i.e. there is no auto-rollback on context cancellation. func (c *Conn) BeginTx(ctx context.Context, txOptions TxOptions) (Tx, error) { _, err := c.Exec(ctx, txOptions.beginSQL()) if err != nil { // begin should never fail unless there is an underlying connection issue or // a context timeout. In either case, the connection is possibly broken. c.die(errors.New("failed to begin transaction")) return nil, err } return &dbTx{conn: c}, nil } // Tx represents a database transaction. // // Tx is an interface instead of a struct to enable connection pools to be implemented without relying on internal pgx // state, to support pseudo-nested transactions with savepoints, and to allow tests to mock transactions. However, // adding a method to an interface is technically a breaking change. If new methods are added to Conn it may be // desirable to add them to Tx as well. Because of this the Tx interface is partially excluded from semantic version // requirements. Methods will not be removed or changed, but new methods may be added. type Tx interface { // Begin starts a pseudo nested transaction. Begin(ctx context.Context) (Tx, error) // Commit commits the transaction if this is a real transaction or releases the savepoint if this is a pseudo nested // transaction. Commit will return an error where errors.Is(ErrTxClosed) is true if the Tx is already closed, but is // otherwise safe to call multiple times. If the commit fails with a rollback status (e.g. the transaction was already // in a broken state) then an error where errors.Is(ErrTxCommitRollback) is true will be returned. Commit(ctx context.Context) error // Rollback rolls back the transaction if this is a real transaction or rolls back to the savepoint if this is a // pseudo nested transaction. Rollback will return an error where errors.Is(ErrTxClosed) is true if the Tx is already // closed, but is otherwise safe to call multiple times. Hence, a defer tx.Rollback() is safe even if tx.Commit() will // be called first in a non-error condition. Any other failure of a real transaction will result in the connection // being closed. Rollback(ctx context.Context) error CopyFrom(ctx context.Context, tableName Identifier, columnNames []string, rowSrc CopyFromSource) (int64, error) SendBatch(ctx context.Context, b *Batch) BatchResults LargeObjects() LargeObjects Prepare(ctx context.Context, name, sql string) (*pgconn.StatementDescription, error) Exec(ctx context.Context, sql string, arguments ...any) (commandTag pgconn.CommandTag, err error) Query(ctx context.Context, sql string, args ...any) (Rows, error) QueryRow(ctx context.Context, sql string, args ...any) Row // Conn returns the underlying *Conn that on which this transaction is executing. Conn() *Conn } // dbTx represents a database transaction. // // All dbTx methods return ErrTxClosed if Commit or Rollback has already been // called on the dbTx. type dbTx struct { conn *Conn err error savepointNum int64 closed bool } // Begin starts a pseudo nested transaction implemented with a savepoint. func (tx *dbTx) Begin(ctx context.Context) (Tx, error) { if tx.closed { return nil, ErrTxClosed } tx.savepointNum++ _, err := tx.conn.Exec(ctx, "savepoint sp_"+strconv.FormatInt(tx.savepointNum, 10)) if err != nil { return nil, err } return &dbSimulatedNestedTx{tx: tx, savepointNum: tx.savepointNum}, nil } // Commit commits the transaction. func (tx *dbTx) Commit(ctx context.Context) error { if tx.closed { return ErrTxClosed } commandTag, err := tx.conn.Exec(ctx, "commit") tx.closed = true if err != nil { if tx.conn.PgConn().TxStatus() != 'I' { _ = tx.conn.Close(ctx) // already have error to return } return err } if commandTag.String() == "ROLLBACK" { return ErrTxCommitRollback } return nil } // Rollback rolls back the transaction. Rollback will return ErrTxClosed if the // Tx is already closed, but is otherwise safe to call multiple times. Hence, a // defer tx.Rollback() is safe even if tx.Commit() will be called first in a // non-error condition. func (tx *dbTx) Rollback(ctx context.Context) error { if tx.closed { return ErrTxClosed } _, err := tx.conn.Exec(ctx, "rollback") tx.closed = true if err != nil { // A rollback failure leaves the connection in an undefined state tx.conn.die(fmt.Errorf("rollback failed: %w", err)) return err } return nil } // Exec delegates to the underlying *Conn func (tx *dbTx) Exec(ctx context.Context, sql string, arguments ...any) (commandTag pgconn.CommandTag, err error) { if tx.closed { return pgconn.CommandTag{}, ErrTxClosed } return tx.conn.Exec(ctx, sql, arguments...) } // Prepare delegates to the underlying *Conn func (tx *dbTx) Prepare(ctx context.Context, name, sql string) (*pgconn.StatementDescription, error) { if tx.closed { return nil, ErrTxClosed } return tx.conn.Prepare(ctx, name, sql) } // Query delegates to the underlying *Conn func (tx *dbTx) Query(ctx context.Context, sql string, args ...any) (Rows, error) { if tx.closed { // Because checking for errors can be deferred to the *Rows, build one with the error err := ErrTxClosed return &baseRows{closed: true, err: err}, err } return tx.conn.Query(ctx, sql, args...) } // QueryRow delegates to the underlying *Conn func (tx *dbTx) QueryRow(ctx context.Context, sql string, args ...any) Row { rows, _ := tx.Query(ctx, sql, args...) return (*connRow)(rows.(*baseRows)) } // CopyFrom delegates to the underlying *Conn func (tx *dbTx) CopyFrom(ctx context.Context, tableName Identifier, columnNames []string, rowSrc CopyFromSource) (int64, error) { if tx.closed { return 0, ErrTxClosed } return tx.conn.CopyFrom(ctx, tableName, columnNames, rowSrc) } // SendBatch delegates to the underlying *Conn func (tx *dbTx) SendBatch(ctx context.Context, b *Batch) BatchResults { if tx.closed { return &batchResults{err: ErrTxClosed} } return tx.conn.SendBatch(ctx, b) } // LargeObjects returns a LargeObjects instance for the transaction. func (tx *dbTx) LargeObjects() LargeObjects { return LargeObjects{tx: tx} } func (tx *dbTx) Conn() *Conn { return tx.conn } // dbSimulatedNestedTx represents a simulated nested transaction implemented by a savepoint. type dbSimulatedNestedTx struct { tx Tx savepointNum int64 closed bool } // Begin starts a pseudo nested transaction implemented with a savepoint. func (sp *dbSimulatedNestedTx) Begin(ctx context.Context) (Tx, error) { if sp.closed { return nil, ErrTxClosed } return sp.tx.Begin(ctx) } // Commit releases the savepoint essentially committing the pseudo nested transaction. func (sp *dbSimulatedNestedTx) Commit(ctx context.Context) error { if sp.closed { return ErrTxClosed } _, err := sp.Exec(ctx, "release savepoint sp_"+strconv.FormatInt(sp.savepointNum, 10)) sp.closed = true return err } // Rollback rolls back to the savepoint essentially rolling back the pseudo nested transaction. Rollback will return // ErrTxClosed if the dbSavepoint is already closed, but is otherwise safe to call multiple times. Hence, a defer sp.Rollback() // is safe even if sp.Commit() will be called first in a non-error condition. func (sp *dbSimulatedNestedTx) Rollback(ctx context.Context) error { if sp.closed { return ErrTxClosed } _, err := sp.Exec(ctx, "rollback to savepoint sp_"+strconv.FormatInt(sp.savepointNum, 10)) sp.closed = true return err } // Exec delegates to the underlying Tx func (sp *dbSimulatedNestedTx) Exec(ctx context.Context, sql string, arguments ...any) (commandTag pgconn.CommandTag, err error) { if sp.closed { return pgconn.CommandTag{}, ErrTxClosed } return sp.tx.Exec(ctx, sql, arguments...) } // Prepare delegates to the underlying Tx func (sp *dbSimulatedNestedTx) Prepare(ctx context.Context, name, sql string) (*pgconn.StatementDescription, error) { if sp.closed { return nil, ErrTxClosed } return sp.tx.Prepare(ctx, name, sql) } // Query delegates to the underlying Tx func (sp *dbSimulatedNestedTx) Query(ctx context.Context, sql string, args ...any) (Rows, error) { if sp.closed { // Because checking for errors can be deferred to the *Rows, build one with the error err := ErrTxClosed return &baseRows{closed: true, err: err}, err } return sp.tx.Query(ctx, sql, args...) } // QueryRow delegates to the underlying Tx func (sp *dbSimulatedNestedTx) QueryRow(ctx context.Context, sql string, args ...any) Row { rows, _ := sp.Query(ctx, sql, args...) return (*connRow)(rows.(*baseRows)) } // CopyFrom delegates to the underlying *Conn func (sp *dbSimulatedNestedTx) CopyFrom(ctx context.Context, tableName Identifier, columnNames []string, rowSrc CopyFromSource) (int64, error) { if sp.closed { return 0, ErrTxClosed } return sp.tx.CopyFrom(ctx, tableName, columnNames, rowSrc) } // SendBatch delegates to the underlying *Conn func (sp *dbSimulatedNestedTx) SendBatch(ctx context.Context, b *Batch) BatchResults { if sp.closed { return &batchResults{err: ErrTxClosed} } return sp.tx.SendBatch(ctx, b) } func (sp *dbSimulatedNestedTx) LargeObjects() LargeObjects { return LargeObjects{tx: sp} } func (sp *dbSimulatedNestedTx) Conn() *Conn { return sp.tx.Conn() } // BeginFunc calls Begin on db and then calls fn. If fn does not return an error then it calls Commit on db. If fn // returns an error it calls Rollback on db. The context will be used when executing the transaction control statements // (BEGIN, ROLLBACK, and COMMIT) but does not otherwise affect the execution of fn. func BeginFunc( ctx context.Context, db interface { Begin(ctx context.Context) (Tx, error) }, fn func(Tx) error, ) (err error) { var tx Tx tx, err = db.Begin(ctx) if err != nil { return err } return beginFuncExec(ctx, tx, fn) } // BeginTxFunc calls BeginTx on db and then calls fn. If fn does not return an error then it calls Commit on db. If fn // returns an error it calls Rollback on db. The context will be used when executing the transaction control statements // (BEGIN, ROLLBACK, and COMMIT) but does not otherwise affect the execution of fn. func BeginTxFunc( ctx context.Context, db interface { BeginTx(ctx context.Context, txOptions TxOptions) (Tx, error) }, txOptions TxOptions, fn func(Tx) error, ) (err error) { var tx Tx tx, err = db.BeginTx(ctx, txOptions) if err != nil { return err } return beginFuncExec(ctx, tx, fn) } func beginFuncExec(ctx context.Context, tx Tx, fn func(Tx) error) (err error) { defer func() { rollbackErr := tx.Rollback(ctx) if rollbackErr != nil && !errors.Is(rollbackErr, ErrTxClosed) { err = rollbackErr } }() fErr := fn(tx) if fErr != nil { _ = tx.Rollback(ctx) // ignore rollback error as there is already an error to return return fErr } return tx.Commit(ctx) }