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db.go
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db.go
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// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package versiondb
import (
"sort"
"strings"
"sync"
"github.com/ava-labs/gecko/database"
"github.com/ava-labs/gecko/database/memdb"
"github.com/ava-labs/gecko/database/nodb"
"github.com/ava-labs/gecko/utils"
)
// 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 prefixed database
func New(db database.Database) *Database {
return &Database{
mem: make(map[string]valueDelete, memdb.DefaultSize),
db: db,
batch: db.NewBatch(),
}
}
// Has implements the database.Database interface
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)
}
// Get implements the database.Database interface
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 utils.CopyBytes(val.value), nil
}
return db.db.Get(key)
}
// Put implements the database.Database interface
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: value}
return nil
}
// Delete implements the database.Database interface
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
}
// NewBatch implements the database.Database interface
func (db *Database) NewBatch() database.Batch { return &batch{db: db} }
// NewIterator implements the database.Database interface
func (db *Database) NewIterator() database.Iterator { return db.NewIteratorWithStartAndPrefix(nil, nil) }
// NewIteratorWithStart implements the database.Database interface
func (db *Database) NewIteratorWithStart(start []byte) database.Iterator {
return db.NewIteratorWithStartAndPrefix(start, nil)
}
// NewIteratorWithPrefix implements the database.Database interface
func (db *Database) NewIteratorWithPrefix(prefix []byte) database.Iterator {
return db.NewIteratorWithStartAndPrefix(nil, prefix)
}
// NewIteratorWithStartAndPrefix implements the database.Database interface
func (db *Database) NewIteratorWithStartAndPrefix(start, prefix []byte) database.Iterator {
db.lock.RLock()
defer db.lock.RUnlock()
if db.mem == nil {
return &nodb.Iterator{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)
}
}
sort.Strings(keys) // Keys need to be in sorted order
values := make([]valueDelete, 0, len(keys))
for _, key := range keys {
values = append(values, db.mem[key])
}
return &iterator{
Iterator: db.db.NewIteratorWithStartAndPrefix(start, prefix),
keys: keys,
values: values,
}
}
// Stat implements the database.Database interface
func (db *Database) Stat(stat string) (string, error) {
db.lock.RLock()
defer db.lock.RUnlock()
if db.mem == nil {
return "", database.ErrClosed
}
return db.db.Stat(stat)
}
// Compact implements the database.Database interface
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() { db.mem = make(map[string]valueDelete, memdb.DefaultSize) }
// 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
}
// Close implements the database.Database interface
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
}
type keyValue struct {
key []byte
value []byte
delete bool
}
type batch struct {
db *Database
writes []keyValue
size int
}
// Put implements the Database interface
func (b *batch) Put(key, value []byte) error {
b.writes = append(b.writes, keyValue{utils.CopyBytes(key), utils.CopyBytes(value), false})
b.size += len(value)
return nil
}
// Delete implements the Database interface
func (b *batch) Delete(key []byte) error {
b.writes = append(b.writes, keyValue{utils.CopyBytes(key), nil, true})
b.size++
return nil
}
// ValueSize implements the Database interface
func (b *batch) ValueSize() int { return b.size }
// Write implements the Database interface
func (b *batch) Write() error {
b.db.lock.Lock()
defer b.db.lock.Unlock()
if b.db.mem == nil {
return database.ErrClosed
}
for _, kv := range b.writes {
b.db.mem[string(kv.key)] = valueDelete{
value: kv.value,
delete: kv.delete,
}
}
return nil
}
// Reset implements the Database interface
func (b *batch) Reset() {
if cap(b.writes) > len(b.writes)*database.MaxExcessCapacityFactor {
b.writes = make([]keyValue, 0, cap(b.writes)/database.CapacityReductionFactor)
} else {
b.writes = b.writes[:0]
}
b.size = 0
}
// Replay implements the Database interface
func (b *batch) Replay(w database.KeyValueWriter) error {
for _, kv := range b.writes {
if kv.delete {
if err := w.Delete(kv.key); err != nil {
return err
}
} else if err := w.Put(kv.key, kv.value); err != nil {
return err
}
}
return nil
}
// Inner returns itself
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 {
database.Iterator
key, value []byte
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 {
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 = it.keys[1:]
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 = it.keys[1:]
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 = it.keys[1:]
it.values = it.values[1:]
it.exhausted = !it.Iterator.Next()
if !memValue.delete {
it.key = []byte(memKey)
it.value = memValue.value
return true
}
}
}
}
}
// Key implements the Iterator interface
func (it *iterator) Key() []byte { return it.key }
// Value implements the Iterator interface
func (it *iterator) Value() []byte { return it.value }
// Release implements the Iterator interface
func (it *iterator) Release() {
it.key = nil
it.value = nil
it.keys = nil
it.values = nil
it.Iterator.Release()
}