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db.go
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db.go
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// Copyright (C) 2019-2024, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package versiondb
import (
"context"
"slices"
"strings"
"sync"
"github.com/ava-labs/avalanchego/database"
"github.com/ava-labs/avalanchego/database/memdb"
)
var (
_ database.Database = (*Database)(nil)
_ Commitable = (*Database)(nil)
_ database.Batch = (*batch)(nil)
_ database.Iterator = (*iterator)(nil)
)
// Commitable defines the interface that specifies that something may be
// committed.
type Commitable interface {
// Commit writes all the queued operations to the underlying data structure.
Commit() error
}
// Database implements the Database interface by living on top of another
// database, writing changes to the underlying database only when commit is
// called.
type Database struct {
lock sync.RWMutex
mem map[string]valueDelete
db database.Database
batch database.Batch
}
type valueDelete struct {
value []byte
delete bool
}
// New returns a new versioned database
func New(db database.Database) *Database {
return &Database{
mem: make(map[string]valueDelete, memdb.DefaultSize),
db: db,
batch: db.NewBatch(),
}
}
func (db *Database) Has(key []byte) (bool, error) {
db.lock.RLock()
defer db.lock.RUnlock()
if db.mem == nil {
return false, database.ErrClosed
}
if val, has := db.mem[string(key)]; has {
return !val.delete, nil
}
return db.db.Has(key)
}
func (db *Database) Get(key []byte) ([]byte, error) {
db.lock.RLock()
defer db.lock.RUnlock()
if db.mem == nil {
return nil, database.ErrClosed
}
if val, has := db.mem[string(key)]; has {
if val.delete {
return nil, database.ErrNotFound
}
return slices.Clone(val.value), nil
}
return db.db.Get(key)
}
func (db *Database) Put(key, value []byte) error {
db.lock.Lock()
defer db.lock.Unlock()
if db.mem == nil {
return database.ErrClosed
}
db.mem[string(key)] = valueDelete{value: slices.Clone(value)}
return nil
}
func (db *Database) Delete(key []byte) error {
db.lock.Lock()
defer db.lock.Unlock()
if db.mem == nil {
return database.ErrClosed
}
db.mem[string(key)] = valueDelete{delete: true}
return nil
}
func (db *Database) NewBatch() database.Batch {
return &batch{db: db}
}
func (db *Database) NewIterator() database.Iterator {
return db.NewIteratorWithStartAndPrefix(nil, nil)
}
func (db *Database) NewIteratorWithStart(start []byte) database.Iterator {
return db.NewIteratorWithStartAndPrefix(start, nil)
}
func (db *Database) NewIteratorWithPrefix(prefix []byte) database.Iterator {
return db.NewIteratorWithStartAndPrefix(nil, prefix)
}
func (db *Database) NewIteratorWithStartAndPrefix(start, prefix []byte) database.Iterator {
db.lock.RLock()
defer db.lock.RUnlock()
if db.mem == nil {
return &database.IteratorError{
Err: database.ErrClosed,
}
}
startString := string(start)
prefixString := string(prefix)
keys := make([]string, 0, len(db.mem))
for key := range db.mem {
if strings.HasPrefix(key, prefixString) && key >= startString {
keys = append(keys, key)
}
}
slices.Sort(keys) // Keys need to be in sorted order
values := make([]valueDelete, len(keys))
for i, key := range keys {
values[i] = db.mem[key]
}
return &iterator{
db: db,
Iterator: db.db.NewIteratorWithStartAndPrefix(start, prefix),
keys: keys,
values: values,
}
}
func (db *Database) Compact(start, limit []byte) error {
db.lock.Lock()
defer db.lock.Unlock()
if db.mem == nil {
return database.ErrClosed
}
return db.db.Compact(start, limit)
}
// SetDatabase changes the underlying database to the specified database
func (db *Database) SetDatabase(newDB database.Database) error {
db.lock.Lock()
defer db.lock.Unlock()
if db.mem == nil {
return database.ErrClosed
}
db.db = newDB
db.batch = newDB.NewBatch()
return nil
}
// GetDatabase returns the underlying database
func (db *Database) GetDatabase() database.Database {
db.lock.RLock()
defer db.lock.RUnlock()
return db.db
}
// Commit writes all the operations of this database to the underlying database
func (db *Database) Commit() error {
db.lock.Lock()
defer db.lock.Unlock()
batch, err := db.commitBatch()
if err != nil {
return err
}
if err := batch.Write(); err != nil {
return err
}
batch.Reset()
db.abort()
return nil
}
// Abort all changes to the underlying database
func (db *Database) Abort() {
db.lock.Lock()
defer db.lock.Unlock()
db.abort()
}
func (db *Database) abort() {
clear(db.mem)
}
// CommitBatch returns a batch that contains all uncommitted puts/deletes.
// Calling Write() on the returned batch causes the puts/deletes to be
// written to the underlying database. The returned batch should be written before
// future calls to this DB unless the batch will never be written.
func (db *Database) CommitBatch() (database.Batch, error) {
db.lock.Lock()
defer db.lock.Unlock()
return db.commitBatch()
}
// Put all of the puts/deletes in memory into db.batch
// and return the batch
func (db *Database) commitBatch() (database.Batch, error) {
if db.mem == nil {
return nil, database.ErrClosed
}
db.batch.Reset()
for key, value := range db.mem {
if value.delete {
if err := db.batch.Delete([]byte(key)); err != nil {
return nil, err
}
} else if err := db.batch.Put([]byte(key), value.value); err != nil {
return nil, err
}
}
return db.batch, nil
}
func (db *Database) Close() error {
db.lock.Lock()
defer db.lock.Unlock()
if db.mem == nil {
return database.ErrClosed
}
db.batch = nil
db.mem = nil
db.db = nil
return nil
}
func (db *Database) isClosed() bool {
db.lock.RLock()
defer db.lock.RUnlock()
return db.db == nil
}
func (db *Database) HealthCheck(ctx context.Context) (interface{}, error) {
db.lock.RLock()
defer db.lock.RUnlock()
if db.mem == nil {
return nil, database.ErrClosed
}
return db.db.HealthCheck(ctx)
}
type batch struct {
database.BatchOps
db *Database
}
func (b *batch) Write() error {
b.db.lock.Lock()
defer b.db.lock.Unlock()
if b.db.mem == nil {
return database.ErrClosed
}
for _, op := range b.Ops {
b.db.mem[string(op.Key)] = valueDelete{
value: op.Value,
delete: op.Delete,
}
}
return nil
}
func (b *batch) Inner() database.Batch {
return b
}
// iterator walks over both the in memory database and the underlying database
// at the same time.
type iterator struct {
db *Database
database.Iterator
key, value []byte
err error
keys []string
values []valueDelete
initialized, exhausted bool
}
// Next moves the iterator to the next key/value pair. It returns whether the
// iterator is exhausted. We must pay careful attention to set the proper values
// based on if the in memory db or the underlying db should be read next
func (it *iterator) Next() bool {
// Short-circuit and set an error if the underlying database has been closed.
if it.db.isClosed() {
it.key = nil
it.value = nil
it.err = database.ErrClosed
return false
}
if !it.initialized {
it.exhausted = !it.Iterator.Next()
it.initialized = true
}
for {
switch {
case it.exhausted && len(it.keys) == 0:
it.key = nil
it.value = nil
return false
case it.exhausted:
nextKey := it.keys[0]
nextValue := it.values[0]
it.keys[0] = ""
it.keys = it.keys[1:]
it.values[0].value = nil
it.values = it.values[1:]
if !nextValue.delete {
it.key = []byte(nextKey)
it.value = nextValue.value
return true
}
case len(it.keys) == 0:
it.key = it.Iterator.Key()
it.value = it.Iterator.Value()
it.exhausted = !it.Iterator.Next()
return true
default:
memKey := it.keys[0]
memValue := it.values[0]
dbKey := it.Iterator.Key()
dbStringKey := string(dbKey)
switch {
case memKey < dbStringKey:
it.keys[0] = ""
it.keys = it.keys[1:]
it.values[0].value = nil
it.values = it.values[1:]
if !memValue.delete {
it.key = []byte(memKey)
it.value = memValue.value
return true
}
case dbStringKey < memKey:
it.key = dbKey
it.value = it.Iterator.Value()
it.exhausted = !it.Iterator.Next()
return true
default:
it.keys[0] = ""
it.keys = it.keys[1:]
it.values[0].value = nil
it.values = it.values[1:]
it.exhausted = !it.Iterator.Next()
if !memValue.delete {
it.key = []byte(memKey)
it.value = memValue.value
return true
}
}
}
}
}
func (it *iterator) Error() error {
if it.err != nil {
return it.err
}
return it.Iterator.Error()
}
func (it *iterator) Key() []byte {
return it.key
}
func (it *iterator) Value() []byte {
return it.value
}
func (it *iterator) Release() {
it.key = nil
it.value = nil
it.keys = nil
it.values = nil
it.Iterator.Release()
}