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