mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-11-19 23:11:02 +00:00
425 lines
13 KiB
Go
425 lines
13 KiB
Go
package pgx
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import (
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"context"
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"errors"
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"fmt"
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"strconv"
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"strings"
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"github.com/jackc/pgx/v5/pgconn"
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)
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// TxIsoLevel is the transaction isolation level (serializable, repeatable read, read committed or read uncommitted)
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type TxIsoLevel string
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// Transaction isolation levels
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const (
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Serializable TxIsoLevel = "serializable"
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RepeatableRead TxIsoLevel = "repeatable read"
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ReadCommitted TxIsoLevel = "read committed"
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ReadUncommitted TxIsoLevel = "read uncommitted"
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)
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// TxAccessMode is the transaction access mode (read write or read only)
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type TxAccessMode string
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// Transaction access modes
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const (
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ReadWrite TxAccessMode = "read write"
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ReadOnly TxAccessMode = "read only"
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)
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// TxDeferrableMode is the transaction deferrable mode (deferrable or not deferrable)
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type TxDeferrableMode string
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// Transaction deferrable modes
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const (
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Deferrable TxDeferrableMode = "deferrable"
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NotDeferrable TxDeferrableMode = "not deferrable"
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)
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// TxOptions are transaction modes within a transaction block
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type TxOptions struct {
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IsoLevel TxIsoLevel
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AccessMode TxAccessMode
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DeferrableMode TxDeferrableMode
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}
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var emptyTxOptions TxOptions
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func (txOptions TxOptions) beginSQL() string {
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if txOptions == emptyTxOptions {
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return "begin"
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}
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var buf strings.Builder
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buf.Grow(64) // 64 - maximum length of string with available options
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buf.WriteString("begin")
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if txOptions.IsoLevel != "" {
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buf.WriteString(" isolation level ")
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buf.WriteString(string(txOptions.IsoLevel))
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}
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if txOptions.AccessMode != "" {
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buf.WriteByte(' ')
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buf.WriteString(string(txOptions.AccessMode))
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}
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if txOptions.DeferrableMode != "" {
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buf.WriteByte(' ')
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buf.WriteString(string(txOptions.DeferrableMode))
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}
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return buf.String()
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}
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var ErrTxClosed = errors.New("tx is closed")
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// ErrTxCommitRollback occurs when an error has occurred in a transaction and
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// Commit() is called. PostgreSQL accepts COMMIT on aborted transactions, but
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// it is treated as ROLLBACK.
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var ErrTxCommitRollback = errors.New("commit unexpectedly resulted in rollback")
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// Begin starts a transaction. Unlike database/sql, the context only affects the begin command. i.e. there is no
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// auto-rollback on context cancellation.
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func (c *Conn) Begin(ctx context.Context) (Tx, error) {
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return c.BeginTx(ctx, TxOptions{})
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}
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// BeginTx starts a transaction with txOptions determining the transaction mode. Unlike database/sql, the context only
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// affects the begin command. i.e. there is no auto-rollback on context cancellation.
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func (c *Conn) BeginTx(ctx context.Context, txOptions TxOptions) (Tx, error) {
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_, err := c.Exec(ctx, txOptions.beginSQL())
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if err != nil {
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// begin should never fail unless there is an underlying connection issue or
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// a context timeout. In either case, the connection is possibly broken.
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c.die(errors.New("failed to begin transaction"))
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return nil, err
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}
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return &dbTx{conn: c}, nil
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}
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// Tx represents a database transaction.
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//
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// Tx is an interface instead of a struct to enable connection pools to be implemented without relying on internal pgx
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// state, to support pseudo-nested transactions with savepoints, and to allow tests to mock transactions. However,
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// adding a method to an interface is technically a breaking change. If new methods are added to Conn it may be
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// desirable to add them to Tx as well. Because of this the Tx interface is partially excluded from semantic version
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// requirements. Methods will not be removed or changed, but new methods may be added.
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type Tx interface {
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// Begin starts a pseudo nested transaction.
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Begin(ctx context.Context) (Tx, error)
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// Commit commits the transaction if this is a real transaction or releases the savepoint if this is a pseudo nested
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// transaction. Commit will return an error where errors.Is(ErrTxClosed) is true if the Tx is already closed, but is
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// otherwise safe to call multiple times. If the commit fails with a rollback status (e.g. the transaction was already
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// in a broken state) then an error where errors.Is(ErrTxCommitRollback) is true will be returned.
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Commit(ctx context.Context) error
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// Rollback rolls back the transaction if this is a real transaction or rolls back to the savepoint if this is a
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// pseudo nested transaction. Rollback will return an error where errors.Is(ErrTxClosed) is true if the Tx is already
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// closed, but is otherwise safe to call multiple times. Hence, a defer tx.Rollback() is safe even if tx.Commit() will
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// be called first in a non-error condition. Any other failure of a real transaction will result in the connection
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// being closed.
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Rollback(ctx context.Context) error
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CopyFrom(ctx context.Context, tableName Identifier, columnNames []string, rowSrc CopyFromSource) (int64, error)
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SendBatch(ctx context.Context, b *Batch) BatchResults
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LargeObjects() LargeObjects
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Prepare(ctx context.Context, name, sql string) (*pgconn.StatementDescription, error)
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Exec(ctx context.Context, sql string, arguments ...any) (commandTag pgconn.CommandTag, err error)
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Query(ctx context.Context, sql string, args ...any) (Rows, error)
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QueryRow(ctx context.Context, sql string, args ...any) Row
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// Conn returns the underlying *Conn that on which this transaction is executing.
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Conn() *Conn
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}
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// dbTx represents a database transaction.
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//
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// All dbTx methods return ErrTxClosed if Commit or Rollback has already been
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// called on the dbTx.
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type dbTx struct {
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conn *Conn
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err error
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savepointNum int64
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closed bool
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}
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// Begin starts a pseudo nested transaction implemented with a savepoint.
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func (tx *dbTx) Begin(ctx context.Context) (Tx, error) {
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if tx.closed {
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return nil, ErrTxClosed
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}
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tx.savepointNum++
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_, err := tx.conn.Exec(ctx, "savepoint sp_"+strconv.FormatInt(tx.savepointNum, 10))
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if err != nil {
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return nil, err
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}
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return &dbSimulatedNestedTx{tx: tx, savepointNum: tx.savepointNum}, nil
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}
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// Commit commits the transaction.
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func (tx *dbTx) Commit(ctx context.Context) error {
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if tx.closed {
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return ErrTxClosed
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}
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commandTag, err := tx.conn.Exec(ctx, "commit")
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tx.closed = true
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if err != nil {
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if tx.conn.PgConn().TxStatus() != 'I' {
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_ = tx.conn.Close(ctx) // already have error to return
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}
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return err
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}
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if commandTag.String() == "ROLLBACK" {
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return ErrTxCommitRollback
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}
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return nil
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}
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// Rollback rolls back the transaction. Rollback will return ErrTxClosed if the
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// Tx is already closed, but is otherwise safe to call multiple times. Hence, a
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// defer tx.Rollback() is safe even if tx.Commit() will be called first in a
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// non-error condition.
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func (tx *dbTx) Rollback(ctx context.Context) error {
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if tx.closed {
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return ErrTxClosed
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}
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_, err := tx.conn.Exec(ctx, "rollback")
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tx.closed = true
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if err != nil {
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// A rollback failure leaves the connection in an undefined state
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tx.conn.die(fmt.Errorf("rollback failed: %w", err))
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return err
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}
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return nil
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}
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// Exec delegates to the underlying *Conn
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func (tx *dbTx) Exec(ctx context.Context, sql string, arguments ...any) (commandTag pgconn.CommandTag, err error) {
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if tx.closed {
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return pgconn.CommandTag{}, ErrTxClosed
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}
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return tx.conn.Exec(ctx, sql, arguments...)
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}
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// Prepare delegates to the underlying *Conn
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func (tx *dbTx) Prepare(ctx context.Context, name, sql string) (*pgconn.StatementDescription, error) {
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if tx.closed {
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return nil, ErrTxClosed
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}
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return tx.conn.Prepare(ctx, name, sql)
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}
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// Query delegates to the underlying *Conn
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func (tx *dbTx) Query(ctx context.Context, sql string, args ...any) (Rows, error) {
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if tx.closed {
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// Because checking for errors can be deferred to the *Rows, build one with the error
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err := ErrTxClosed
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return &baseRows{closed: true, err: err}, err
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}
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return tx.conn.Query(ctx, sql, args...)
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}
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// QueryRow delegates to the underlying *Conn
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func (tx *dbTx) QueryRow(ctx context.Context, sql string, args ...any) Row {
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rows, _ := tx.Query(ctx, sql, args...)
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return (*connRow)(rows.(*baseRows))
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}
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// CopyFrom delegates to the underlying *Conn
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func (tx *dbTx) CopyFrom(ctx context.Context, tableName Identifier, columnNames []string, rowSrc CopyFromSource) (int64, error) {
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if tx.closed {
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return 0, ErrTxClosed
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}
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return tx.conn.CopyFrom(ctx, tableName, columnNames, rowSrc)
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}
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// SendBatch delegates to the underlying *Conn
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func (tx *dbTx) SendBatch(ctx context.Context, b *Batch) BatchResults {
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if tx.closed {
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return &batchResults{err: ErrTxClosed}
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}
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return tx.conn.SendBatch(ctx, b)
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}
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// LargeObjects returns a LargeObjects instance for the transaction.
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func (tx *dbTx) LargeObjects() LargeObjects {
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return LargeObjects{tx: tx}
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}
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func (tx *dbTx) Conn() *Conn {
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return tx.conn
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}
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// dbSimulatedNestedTx represents a simulated nested transaction implemented by a savepoint.
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type dbSimulatedNestedTx struct {
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tx Tx
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savepointNum int64
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closed bool
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}
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// Begin starts a pseudo nested transaction implemented with a savepoint.
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func (sp *dbSimulatedNestedTx) Begin(ctx context.Context) (Tx, error) {
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if sp.closed {
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return nil, ErrTxClosed
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}
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return sp.tx.Begin(ctx)
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}
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// Commit releases the savepoint essentially committing the pseudo nested transaction.
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func (sp *dbSimulatedNestedTx) Commit(ctx context.Context) error {
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if sp.closed {
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return ErrTxClosed
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}
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_, err := sp.Exec(ctx, "release savepoint sp_"+strconv.FormatInt(sp.savepointNum, 10))
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sp.closed = true
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return err
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}
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// Rollback rolls back to the savepoint essentially rolling back the pseudo nested transaction. Rollback will return
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// ErrTxClosed if the dbSavepoint is already closed, but is otherwise safe to call multiple times. Hence, a defer sp.Rollback()
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// is safe even if sp.Commit() will be called first in a non-error condition.
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func (sp *dbSimulatedNestedTx) Rollback(ctx context.Context) error {
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if sp.closed {
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return ErrTxClosed
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}
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_, err := sp.Exec(ctx, "rollback to savepoint sp_"+strconv.FormatInt(sp.savepointNum, 10))
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sp.closed = true
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return err
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}
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// Exec delegates to the underlying Tx
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func (sp *dbSimulatedNestedTx) Exec(ctx context.Context, sql string, arguments ...any) (commandTag pgconn.CommandTag, err error) {
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if sp.closed {
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return pgconn.CommandTag{}, ErrTxClosed
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}
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return sp.tx.Exec(ctx, sql, arguments...)
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}
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// Prepare delegates to the underlying Tx
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func (sp *dbSimulatedNestedTx) Prepare(ctx context.Context, name, sql string) (*pgconn.StatementDescription, error) {
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if sp.closed {
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return nil, ErrTxClosed
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}
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return sp.tx.Prepare(ctx, name, sql)
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}
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// Query delegates to the underlying Tx
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func (sp *dbSimulatedNestedTx) Query(ctx context.Context, sql string, args ...any) (Rows, error) {
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if sp.closed {
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// Because checking for errors can be deferred to the *Rows, build one with the error
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err := ErrTxClosed
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return &baseRows{closed: true, err: err}, err
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}
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return sp.tx.Query(ctx, sql, args...)
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}
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// QueryRow delegates to the underlying Tx
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func (sp *dbSimulatedNestedTx) QueryRow(ctx context.Context, sql string, args ...any) Row {
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rows, _ := sp.Query(ctx, sql, args...)
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return (*connRow)(rows.(*baseRows))
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}
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// CopyFrom delegates to the underlying *Conn
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func (sp *dbSimulatedNestedTx) CopyFrom(ctx context.Context, tableName Identifier, columnNames []string, rowSrc CopyFromSource) (int64, error) {
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if sp.closed {
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return 0, ErrTxClosed
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}
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return sp.tx.CopyFrom(ctx, tableName, columnNames, rowSrc)
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}
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// SendBatch delegates to the underlying *Conn
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func (sp *dbSimulatedNestedTx) SendBatch(ctx context.Context, b *Batch) BatchResults {
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if sp.closed {
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return &batchResults{err: ErrTxClosed}
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}
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return sp.tx.SendBatch(ctx, b)
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}
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func (sp *dbSimulatedNestedTx) LargeObjects() LargeObjects {
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return LargeObjects{tx: sp}
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}
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func (sp *dbSimulatedNestedTx) Conn() *Conn {
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return sp.tx.Conn()
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}
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// BeginFunc calls Begin on db and then calls fn. If fn does not return an error then it calls Commit on db. If fn
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// returns an error it calls Rollback on db. The context will be used when executing the transaction control statements
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// (BEGIN, ROLLBACK, and COMMIT) but does not otherwise affect the execution of fn.
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func BeginFunc(
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ctx context.Context,
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db interface {
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Begin(ctx context.Context) (Tx, error)
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},
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fn func(Tx) error,
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) (err error) {
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var tx Tx
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tx, err = db.Begin(ctx)
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if err != nil {
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return err
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}
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return beginFuncExec(ctx, tx, fn)
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}
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// BeginTxFunc calls BeginTx on db and then calls fn. If fn does not return an error then it calls Commit on db. If fn
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// returns an error it calls Rollback on db. The context will be used when executing the transaction control statements
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// (BEGIN, ROLLBACK, and COMMIT) but does not otherwise affect the execution of fn.
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func BeginTxFunc(
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ctx context.Context,
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db interface {
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BeginTx(ctx context.Context, txOptions TxOptions) (Tx, error)
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},
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txOptions TxOptions,
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fn func(Tx) error,
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) (err error) {
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var tx Tx
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tx, err = db.BeginTx(ctx, txOptions)
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if err != nil {
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return err
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}
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return beginFuncExec(ctx, tx, fn)
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}
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func beginFuncExec(ctx context.Context, tx Tx, fn func(Tx) error) (err error) {
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defer func() {
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rollbackErr := tx.Rollback(ctx)
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if rollbackErr != nil && !errors.Is(rollbackErr, ErrTxClosed) {
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err = rollbackErr
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}
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}()
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fErr := fn(tx)
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if fErr != nil {
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_ = tx.Rollback(ctx) // ignore rollback error as there is already an error to return
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return fErr
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}
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return tx.Commit(ctx)
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}
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