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tiered.go
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tiered.go
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package tiered
import (
"fmt"
"sync"
ds "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
dsq "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
)
type tiered []ds.Datastore
// New returns a tiered datastore. Puts and Deletes will write-through to
// all datastores, Has and Get will try each datastore sequentially, and
// Query will always try the last one (most complete) first.
func New(dses ...ds.Datastore) ds.Datastore {
return tiered(dses)
}
// Put stores the object `value` named by `key`.
func (d tiered) Put(key ds.Key, value interface{}) (err error) {
errs := make(chan error, len(d))
var wg sync.WaitGroup
for _, cd := range d {
wg.Add(1)
go func(cd ds.Datastore) {
defer wg.Done()
if err := cd.Put(key, value); err != nil {
errs <- err
}
}(cd)
}
wg.Wait()
close(errs)
for err := range errs {
return err
}
return nil
}
// Get retrieves the object `value` named by `key`.
func (d tiered) Get(key ds.Key) (value interface{}, err error) {
err = fmt.Errorf("no datastores")
for _, cd := range d {
value, err = cd.Get(key)
if err == nil {
break
}
}
return
}
// Has returns whether the `key` is mapped to a `value`.
func (d tiered) Has(key ds.Key) (exists bool, err error) {
err = fmt.Errorf("no datastores")
for _, cd := range d {
exists, err = cd.Has(key)
if err == nil && exists {
break
}
}
return
}
// Delete removes the value for given `key`.
func (d tiered) Delete(key ds.Key) (err error) {
errs := make(chan error, len(d))
var wg sync.WaitGroup
for _, cd := range d {
wg.Add(1)
go func(cd ds.Datastore) {
defer wg.Done()
if err := cd.Delete(key); err != nil {
errs <- err
}
}(cd)
}
wg.Wait()
close(errs)
for err := range errs {
return err
}
return nil
}
// Query returns a list of keys in the datastore
func (d tiered) Query(q dsq.Query) (dsq.Results, error) {
// query always the last (most complete) one
return d[len(d)-1].Query(q)
}