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package bbolt
// Compact will create a copy of the source DB and in the destination DB. This may
// reclaim space that the source database no longer has use for. txMaxSize can be
// used to limit the transactions size of this process and may trigger intermittent
// commits. A value of zero will ignore transaction sizes.
// TODO: merge with: https://github.com/etcd-io/etcd/blob/b7f0f52a16dbf83f18ca1d803f7892d750366a94/mvcc/backend/backend.go#L349
func Compact(dst, src *DB, txMaxSize int64) error {
// commit regularly, or we'll run out of memory for large datasets if using one transaction.
var size int64
tx, err := dst.Begin(true)
if err != nil {
return err
}
defer tx.Rollback()
if err := walk(src, func(keys [][]byte, k, v []byte, seq uint64) error {
// On each key/value, check if we have exceeded tx size.
sz := int64(len(k) + len(v))
if size+sz > txMaxSize && txMaxSize != 0 {
// Commit previous transaction.
if err := tx.Commit(); err != nil {
return err
}
// Start new transaction.
tx, err = dst.Begin(true)
if err != nil {
return err
}
size = 0
}
size += sz
// Create bucket on the root transaction if this is the first level.
nk := len(keys)
if nk == 0 {
bkt, err := tx.CreateBucket(k)
if err != nil {
return err
}
if err := bkt.SetSequence(seq); err != nil {
return err
}
return nil
}
// Create buckets on subsequent levels, if necessary.
b := tx.Bucket(keys[0])
if nk > 1 {
for _, k := range keys[1:] {
b = b.Bucket(k)
}
}
// Fill the entire page for best compaction.
b.FillPercent = 1.0
// If there is no value then this is a bucket call.
if v == nil {
bkt, err := b.CreateBucket(k)
if err != nil {
return err
}
if err := bkt.SetSequence(seq); err != nil {
return err
}
return nil
}
// Otherwise treat it as a key/value pair.
return b.Put(k, v)
}); err != nil {
return err
}
return tx.Commit()
}
// walkFunc is the type of the function called for keys (buckets and "normal"
// values) discovered by Walk. keys is the list of keys to descend to the bucket
// owning the discovered key/value pair k/v.
type walkFunc func(keys [][]byte, k, v []byte, seq uint64) error
// walk walks recursively the bolt database db, calling walkFn for each key it finds.
func walk(db *DB, walkFn walkFunc) error {
return db.View(func(tx *Tx) error {
return tx.ForEach(func(name []byte, b *Bucket) error {
return walkBucket(b, nil, name, nil, b.Sequence(), walkFn)
})
})
}
func walkBucket(b *Bucket, keypath [][]byte, k, v []byte, seq uint64, fn walkFunc) error {
// Execute callback.
if err := fn(keypath, k, v, seq); err != nil {
return err
}
// If this is not a bucket then stop.
if v != nil {
return nil
}
// Iterate over each child key/value.
keypath = append(keypath, k)
return b.ForEach(func(k, v []byte) error {
if v == nil {
bkt := b.Bucket(k)
return walkBucket(bkt, keypath, k, nil, bkt.Sequence(), fn)
}
return walkBucket(b, keypath, k, v, b.Sequence(), fn)
})
}
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