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feat: more compact exported snapshot (#703)
Co-authored-by: cool-developer <[email protected]> Co-authored-by: Marko <[email protected]>
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Apr 6, 2023
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,144 @@ | ||
| package iavl | ||
|
|
||
| import ( | ||
| "encoding/binary" | ||
| "fmt" | ||
| ) | ||
|
|
||
| type NodeExporter interface { | ||
| Next() (*ExportNode, error) | ||
| } | ||
|
|
||
| type NodeImporter interface { | ||
| Add(*ExportNode) error | ||
| } | ||
|
|
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| // CompressExporter wraps the normal exporter to apply some compressions on `ExportNode`: | ||
| // - branch keys are skipped | ||
| // - leaf keys are encoded with delta compared with the previous leaf | ||
| // - branch node's version are encoded with delta compared with the max version in it's children | ||
| type CompressExporter struct { | ||
| inner NodeExporter | ||
| lastKey []byte | ||
| versionStack []int64 | ||
| } | ||
|
|
||
| var _ NodeExporter = (*CompressExporter)(nil) | ||
|
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| func NewCompressExporter(exporter NodeExporter) NodeExporter { | ||
| return &CompressExporter{inner: exporter} | ||
| } | ||
|
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| func (e *CompressExporter) Next() (*ExportNode, error) { | ||
| n, err := e.inner.Next() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
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| if n.Height == 0 { | ||
| // apply delta encoding to leaf keys | ||
| n.Key, e.lastKey = deltaEncode(n.Key, e.lastKey), n.Key | ||
|
|
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| e.versionStack = append(e.versionStack, n.Version) | ||
| } else { | ||
| // branch keys can be derived on the fly when import, safe to skip | ||
| n.Key = nil | ||
|
|
||
| // delta encode the version | ||
| maxVersion := maxInt64(e.versionStack[len(e.versionStack)-1], e.versionStack[len(e.versionStack)-2]) | ||
| e.versionStack = e.versionStack[:len(e.versionStack)-1] | ||
| e.versionStack[len(e.versionStack)-1] = n.Version | ||
| n.Version -= maxVersion | ||
| } | ||
|
|
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| return n, nil | ||
| } | ||
|
|
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| // CompressImporter wraps the normal importer to do de-compressions before hand. | ||
| type CompressImporter struct { | ||
| inner NodeImporter | ||
| lastKey []byte | ||
| minKeyStack [][]byte | ||
| versionStack []int64 | ||
| } | ||
|
|
||
| var _ NodeImporter = (*CompressImporter)(nil) | ||
|
|
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| func NewCompressImporter(importer NodeImporter) NodeImporter { | ||
| return &CompressImporter{inner: importer} | ||
| } | ||
|
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| func (i *CompressImporter) Add(node *ExportNode) error { | ||
| if node.Height == 0 { | ||
| key, err := deltaDecode(node.Key, i.lastKey) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| node.Key = key | ||
| i.lastKey = key | ||
|
|
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| i.minKeyStack = append(i.minKeyStack, key) | ||
| i.versionStack = append(i.versionStack, node.Version) | ||
| } else { | ||
| // use the min-key in right branch as the node key | ||
| node.Key = i.minKeyStack[len(i.minKeyStack)-1] | ||
| // leave the min-key in left branch in the stack | ||
| i.minKeyStack = i.minKeyStack[:len(i.minKeyStack)-1] | ||
|
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| // decode branch node version | ||
| maxVersion := maxInt64(i.versionStack[len(i.versionStack)-1], i.versionStack[len(i.versionStack)-2]) | ||
| node.Version += maxVersion | ||
| i.versionStack = i.versionStack[:len(i.versionStack)-1] | ||
| i.versionStack[len(i.versionStack)-1] = node.Version | ||
| } | ||
|
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| return i.inner.Add(node) | ||
| } | ||
|
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| func deltaEncode(key, lastKey []byte) []byte { | ||
| var sizeBuf [binary.MaxVarintLen64]byte | ||
| shared := diffOffset(lastKey, key) | ||
| n := binary.PutUvarint(sizeBuf[:], uint64(shared)) | ||
| return append(sizeBuf[:n], key[shared:]...) | ||
| } | ||
|
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| func deltaDecode(key, lastKey []byte) ([]byte, error) { | ||
| shared, n := binary.Uvarint(key) | ||
| if n <= 0 { | ||
| return nil, fmt.Errorf("uvarint parse failed %d", n) | ||
| } | ||
|
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| key = key[n:] | ||
| if shared == 0 { | ||
| return key, nil | ||
| } | ||
|
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| newKey := make([]byte, shared+uint64(len(key))) | ||
| copy(newKey, lastKey[:shared]) | ||
| copy(newKey[shared:], key) | ||
| return newKey, nil | ||
| } | ||
|
|
||
| // diffOffset returns the index of first byte that's different in two bytes slice. | ||
| func diffOffset(a, b []byte) int { | ||
| var off int | ||
| var l int | ||
| if len(a) < len(b) { | ||
| l = len(a) | ||
| } else { | ||
| l = len(b) | ||
| } | ||
| for ; off < l; off++ { | ||
| if a[off] != b[off] { | ||
| break | ||
| } | ||
| } | ||
| return off | ||
| } | ||
|
|
||
| func maxInt64(a, b int64) int64 { | ||
| if a > b { | ||
| return a | ||
| } | ||
| return b | ||
| } |
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