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// Copyright 2014 The Cockroach Authors.
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt.
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.
package batcheval
import (
// A Command is the implementation of a single request within a BatchRequest.
type Command struct {
// DeclareKeys adds all keys this command touches to the given SpanSet.
// TODO(nvanbenschoten): rationalize this RangeDescriptor. Can it change
// between key declaration and cmd evaluation?
DeclareKeys func(*roachpb.RangeDescriptor, roachpb.Header, roachpb.Request, *spanset.SpanSet)
// Eval evaluates a command on the given engine. It should populate the
// supplied response (always a non-nil pointer to the correct type) and
// return special side effects (if any) in the Result. If it writes to the
// engine it should also update *CommandArgs.Stats. It should treat the
// provided request as immutable.
Eval func(context.Context, engine.ReadWriter, CommandArgs, roachpb.Response) (result.Result, error)
var cmds = make(map[roachpb.Method]Command)
// RegisterCommand makes a command available for execution. It must only be
// called before any evaluation takes place.
func RegisterCommand(
method roachpb.Method,
declare func(*roachpb.RangeDescriptor, roachpb.Header, roachpb.Request, *spanset.SpanSet),
impl func(context.Context, engine.ReadWriter, CommandArgs, roachpb.Response) (result.Result, error),
) {
if _, ok := cmds[method]; ok {
log.Fatalf(context.TODO(), "cannot overwrite previously registered method %v", method)
cmds[method] = Command{
DeclareKeys: declare,
Eval: impl,
// UnregisterCommand is provided for testing and allows removing a command.
// It is a no-op if the command is not registered.
func UnregisterCommand(method roachpb.Method) {
delete(cmds, method)
// LookupCommand returns the command for the given method, with the boolean
// indicating success or failure.
func LookupCommand(method roachpb.Method) (Command, bool) {
cmd, ok := cmds[method]
return cmd, ok
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