func (daemon *Daemon) ImageGetCached(imgID string, config *runconfig.Config) (*image.Image, error) {
	// Retrieve all images
	images := daemon.Graph().Map()

	// Store the tree in a map of map (map[parentId][childId])
	imageMap := make(map[string]map[string]struct{})
	for _, img := range images {
		if _, exists := imageMap[img.Parent]; !exists {
			imageMap[img.Parent] = make(map[string]struct{})
		}
		imageMap[img.Parent][img.ID] = struct{}{}
	}

	// Loop on the children of the given image and check the config
	var match *image.Image
	for elem := range imageMap[imgID] {
		img, ok := images[elem]
		if !ok {
			return nil, fmt.Errorf("unable to find image %q", elem)
		}
		if runconfig.Compare(&img.ContainerConfig, config) {
			if match == nil || match.Created.Before(img.Created) {
				match = img
			}
		}
	}
	return match, nil
}

// ImageGetCached returns the earliest created image that is a child
// of the image with imgID, that had the same config when it was
// created. nil is returned if a child cannot be found. An error is
// returned if the parent image cannot be found.
func (daemon *Daemon) ImageGetCached(imgID image.ID, config *runconfig.Config) (*image.Image, error) {
	// Retrieve all images
	imgs := daemon.Map()

	var siblings []image.ID
	for id, img := range imgs {
		if img.Parent == imgID {
			siblings = append(siblings, id)
		}
	}

	// Loop on the children of the given image and check the config
	var match *image.Image
	for _, id := range siblings {
		img, ok := imgs[id]
		if !ok {
			return nil, fmt.Errorf("unable to find image %q", id)
		}
		if runconfig.Compare(&img.ContainerConfig, config) {
			if match == nil || match.Created.Before(img.Created) {
				match = img
			}
		}
	}
	return match, nil
}

// GetCachedImage returns the most recent created image that is a child
// of the image with imgID, that had the same config when it was
// created. nil is returned if a child cannot be found. An error is
// returned if the parent image cannot be found.
func (daemon *Daemon) GetCachedImage(imgID image.ID, config *containertypes.Config) (*image.Image, error) {
	// Loop on the children of the given image and check the config
	getMatch := func(siblings []image.ID) (*image.Image, error) {
		var match *image.Image
		for _, id := range siblings {
			img, err := daemon.imageStore.Get(id)
			if err != nil {
				return nil, fmt.Errorf("unable to find image %q", id)
			}

			if runconfig.Compare(&img.ContainerConfig, config) {
				// check for the most up to date match
				if match == nil || match.Created.Before(img.Created) {
					match = img
				}
			}
		}
		return match, nil
	}

	// In this case, this is `FROM scratch`, which isn't an actual image.
	if imgID == "" {
		images := daemon.imageStore.Map()
		var siblings []image.ID
		for id, img := range images {
			if img.Parent == imgID {
				siblings = append(siblings, id)
			}
		}
		return getMatch(siblings)
	}

	// find match from child images
	siblings := daemon.imageStore.Children(imgID)
	return getMatch(siblings)
}

// ImageGetCached returns the earliest created image that is a child
// of the image with imgID, that had the same config when it was
// created. nil is returned if a child cannot be found. An error is
// returned if the parent image cannot be found.
func (daemon *Daemon) ImageGetCached(imgID string, config *runconfig.Config) (*image.Image, error) {
	// for now just exit if imgID has no children.
	// maybe parentRefs in graph could be used to store
	// the Image obj children for faster lookup below but this can
	// be quite memory hungry.
	if !daemon.Graph().HasChildren(imgID) {
		return nil, nil
	}

	// Retrieve all images
	images := daemon.Graph().Map()

	// Store the tree in a map of map (map[parentId][childId])
	imageMap := make(map[string]map[string]struct{})
	for _, img := range images {
		if _, exists := imageMap[img.Parent]; !exists {
			imageMap[img.Parent] = make(map[string]struct{})
		}
		imageMap[img.Parent][img.ID] = struct{}{}
	}

	// Loop on the children of the given image and check the config
	var match *image.Image
	for elem := range imageMap[imgID] {
		img, ok := images[elem]
		if !ok {
			return nil, fmt.Errorf("unable to find image %q", elem)
		}
		if runconfig.Compare(&img.ContainerConfig, config) {
			if match == nil || match.Created.Before(img.Created) {
				match = img
			}
		}
	}
	return match, nil
}