context

type Context interface {
	// NewTxn creates a new transaction for further execution.
	// If old transaction is valid, it is committed first.
	// It's used in BEGIN statement and DDL statements to commit old transaction.
	NewTxn() error

	// Txn returns the current transaction which is created before executing a statement.
	Txn() kv.Transaction

	// GetClient gets a kv.Client.
	GetClient() kv.Client

	// SetValue saves a value associated with this context for key.
	SetValue(key fmt.Stringer, value interface{})

	// Value returns the value associated with this context for key.
	Value(key fmt.Stringer) interface{}

	// ClearValue clears the value associated with this context for key.
	ClearValue(key fmt.Stringer)

	GetSessionVars() *variable.SessionVars

	GetSessionManager() util.SessionManager

	// ActivePendingTxn receives the pending transaction from the transaction channel.
	// It should be called right before we builds an executor.
	ActivePendingTxn() error

	// InitTxnWithStartTS initializes a transaction with startTS.
	// It should be called right before we builds an executor.
	InitTxnWithStartTS(startTS uint64) error

	// Done returns a channel for cancellation, the same as standard context.Context.
	// See https://godoc.org/context for more examples of how to use it.
	Done() <-chan struct{}
}

type CtxForCancel struct {
	Context
}