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226 lines (186 loc) · 5.95 KB
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package pgx
import (
"bytes"
"context"
"fmt"
"time"
"github.com/pkg/errors"
)
type TxIsoLevel string
// Transaction isolation levels
const (
Serializable = TxIsoLevel("serializable")
RepeatableRead = TxIsoLevel("repeatable read")
ReadCommitted = TxIsoLevel("read committed")
ReadUncommitted = TxIsoLevel("read uncommitted")
)
type TxAccessMode string
// Transaction access modes
const (
ReadWrite = TxAccessMode("read write")
ReadOnly = TxAccessMode("read only")
)
type TxDeferrableMode string
// Transaction deferrable modes
const (
Deferrable = TxDeferrableMode("deferrable")
NotDeferrable = TxDeferrableMode("not deferrable")
)
const (
TxStatusInProgress = 0
TxStatusCommitFailure = -1
TxStatusRollbackFailure = -2
TxStatusCommitSuccess = 1
TxStatusRollbackSuccess = 2
)
type TxOptions struct {
IsoLevel TxIsoLevel
AccessMode TxAccessMode
DeferrableMode TxDeferrableMode
}
func (txOptions *TxOptions) beginSQL() string {
if txOptions == nil {
return "begin"
}
buf := &bytes.Buffer{}
buf.WriteString("begin")
if txOptions.IsoLevel != "" {
fmt.Fprintf(buf, " isolation level %s", txOptions.IsoLevel)
}
if txOptions.AccessMode != "" {
fmt.Fprintf(buf, " %s", txOptions.AccessMode)
}
if txOptions.DeferrableMode != "" {
fmt.Fprintf(buf, " %s", 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 with the default transaction mode for the
// current connection. To use a specific transaction mode see BeginEx.
func (c *Conn) Begin() (*Tx, error) {
return c.BeginEx(context.Background(), nil)
}
// BeginEx 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 cancelation.
func (c *Conn) BeginEx(ctx context.Context, txOptions *TxOptions) (*Tx, error) {
_, err := c.ExecEx(ctx, txOptions.beginSQL(), nil)
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 &Tx{conn: c}, nil
}
// Tx represents a database transaction.
//
// All Tx methods return ErrTxClosed if Commit or Rollback has already been
// called on the Tx.
type Tx struct {
conn *Conn
connPool *ConnPool
err error
status int8
}
// Commit commits the transaction
func (tx *Tx) Commit() error {
return tx.CommitEx(context.Background())
}
// CommitEx commits the transaction with a context.
func (tx *Tx) CommitEx(ctx context.Context) error {
if tx.status != TxStatusInProgress {
return ErrTxClosed
}
commandTag, err := tx.conn.ExecEx(ctx, "commit", nil)
if err == nil && commandTag == "COMMIT" {
tx.status = TxStatusCommitSuccess
} else if err == nil && commandTag == "ROLLBACK" {
tx.status = TxStatusCommitFailure
tx.err = ErrTxCommitRollback
} else {
tx.status = TxStatusCommitFailure
tx.err = err
// A commit failure leaves the connection in an undefined state
tx.conn.die(errors.New("commit failed"))
}
if tx.connPool != nil {
tx.connPool.Release(tx.conn)
}
return tx.err
}
// 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 *Tx) Rollback() error {
if tx.status != TxStatusInProgress {
return ErrTxClosed
}
ctx, _ := context.WithTimeout(context.Background(), 15*time.Second)
_, tx.err = tx.conn.ExecEx(ctx, "rollback", nil)
if tx.err == nil {
tx.status = TxStatusRollbackSuccess
} else {
tx.status = TxStatusRollbackFailure
// A rollback failure leaves the connection in an undefined state
tx.conn.die(errors.New("rollback failed"))
}
if tx.connPool != nil {
tx.connPool.Release(tx.conn)
}
return tx.err
}
// Exec delegates to the underlying *Conn
func (tx *Tx) Exec(sql string, arguments ...interface{}) (commandTag CommandTag, err error) {
if tx.status != TxStatusInProgress {
return CommandTag(""), ErrTxClosed
}
return tx.conn.Exec(sql, arguments...)
}
// Prepare delegates to the underlying *Conn
func (tx *Tx) Prepare(name, sql string) (*PreparedStatement, error) {
return tx.PrepareEx(context.Background(), name, sql, nil)
}
// PrepareEx delegates to the underlying *Conn
func (tx *Tx) PrepareEx(ctx context.Context, name, sql string, opts *PrepareExOptions) (*PreparedStatement, error) {
if tx.status != TxStatusInProgress {
return nil, ErrTxClosed
}
return tx.conn.PrepareEx(ctx, name, sql, opts)
}
// Query delegates to the underlying *Conn
func (tx *Tx) Query(sql string, args ...interface{}) (*Rows, error) {
if tx.status != TxStatusInProgress {
// Because checking for errors can be deferred to the *Rows, build one with the error
err := ErrTxClosed
return &Rows{closed: true, err: err}, err
}
return tx.conn.Query(sql, args...)
}
// QueryRow delegates to the underlying *Conn
func (tx *Tx) QueryRow(sql string, args ...interface{}) *Row {
rows, _ := tx.Query(sql, args...)
return (*Row)(rows)
}
// CopyFrom delegates to the underlying *Conn
func (tx *Tx) CopyFrom(tableName Identifier, columnNames []string, rowSrc CopyFromSource) (int, error) {
if tx.status != TxStatusInProgress {
return 0, ErrTxClosed
}
return tx.conn.CopyFrom(tableName, columnNames, rowSrc)
}
// Status returns the status of the transaction from the set of
// pgx.TxStatus* constants.
func (tx *Tx) Status() int8 {
return tx.status
}
// Err returns the final error state, if any, of calling Commit or Rollback.
func (tx *Tx) Err() error {
return tx.err
}