// GetMulti returns several objects with only one trip to the cache.
// The queried keys are the ones set in the out parameter. Any key present
// in out and not found when querying the cache, will be deleted. The initial
// values in the out map should be any value of the type which will be used
// to decode the data for the given key.
// e.g. Let's suppose our cache holds 3 objects: k1 of type []int, k2 of type
// float64 and k3 of type string. To query for these 3 objects using GetMulti
// you would initialze out like this:
//
// out := map[string]interface{}{
// k1: []int(nil),
// k2: float(0),
// k3: "",
// }
// err := c.GetMulti(out, nil)
//
// After the GetMulti() call, any keys not present in the cache will be
// deleted from out, so len(out) will be <= 3 in this example.
//
// Alternatively, the second argument might be used to specify the types
// of the object to be decoded. Users might implement their own Typer
// or use UniTyper when requesting several objects of the same type.
func (c *Cache) GetMulti(out map[string]interface{}, typer Typer) error {
keys := make([]string, 0, len(out))
for k := range out {
keys = append(keys, k)
}
if profile.On && profile.Profiling() {
defer profile.Startf(cache, "GET MULTI", "%v", keys).End()
}
qkeys := keys
if c.prefixLen > 0 {
qkeys = make([]string, len(keys))
for ii, v := range keys {
qkeys[ii] = c.backendKey(v)
}
}
data, err := c.driver.GetMulti(qkeys)
if err != nil {
gerr := &cacheError{
op: "getting multiple keys",
key: strings.Join(keys, ", "),
err: err,
}
c.error(gerr)
return gerr
}
if typer == nil {
typer = mapTyper(out)
}
for ii, k := range keys {
value := data[qkeys[ii]]
if value == nil {
delete(out, k)
continue
}
typ := typer.Type(k)
if typ == nil {
derr := &cacheError{
op: "determining output type for object",
key: k,
err: fmt.Errorf("untyped value for key %q - please, set the value type like e.g. out[%q] = ([]int)(nil) or out[%q] = float64(0)", k, k, k),
}
c.error(derr)
return derr
}
val := reflect.New(typ)
err := c.codec.Decode(value, val.Interface())
if err != nil {
derr := &cacheError{
op: "decoding object",
key: k,
err: err,
}
c.error(derr)
return derr
}
out[k] = val.Elem().Interface()
}
return nil
}
// Delete removes the key from the cache. An error is returned only
// if the item was found but couldn't be deleted. Deleting a non-existant
// item is always successful.
func (c *Cache) Delete(key string) error {
if profile.On {
defer profile.Startf(cache, "DELETE %s", key).End()
}
err := c.driver.Delete(c.backendKey(key))
if err != nil {
derr := &cacheError{
op: "deleting",
key: key,
err: err,
}
c.error(derr)
return derr
}
return nil
}