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db.go
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db.go
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// Copyright (c) 2017-2018 The qitmeer developers
// Copyright (c) 2015-2016 The btcsuite developers
// Copyright (c) 2016 The Decred developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package ffldb
import (
"bytes"
"encoding/binary"
"fmt"
"os"
"path/filepath"
"runtime"
"sort"
"sync"
"github.com/Qitmeer/qitmeer/common/hash"
"github.com/Qitmeer/qitmeer/core/protocol"
"github.com/Qitmeer/qitmeer/core/types"
"github.com/Qitmeer/qitmeer/database"
"github.com/Qitmeer/qitmeer/database/ffldb/treap"
"github.com/syndtr/goleveldb/leveldb"
"github.com/syndtr/goleveldb/leveldb/comparer"
ldberrors "github.com/syndtr/goleveldb/leveldb/errors"
"github.com/syndtr/goleveldb/leveldb/filter"
"github.com/syndtr/goleveldb/leveldb/iterator"
"github.com/syndtr/goleveldb/leveldb/opt"
"github.com/syndtr/goleveldb/leveldb/util"
)
const (
// metadataDbName is the name used for the metadata database.
metadataDbName = "metadata"
// blockHdrSize is the size of a block header. This is simply the
// constant from wire and is only provided here for convenience since
// wire.MaxBlockHeaderPayload is quite long.
blockHdrSize = types.MaxBlockHeaderPayload
// blockHdrOffset defines the offsets into a block index row for the
// block header.
//
// The serialized block index row format is:
// <blocklocation><blockheader>
blockHdrOffset = blockLocSize
)
var (
// byteOrder is the preferred byte order used through the database and
// block files. Sometimes big endian will be used to allow ordered byte
// sortable integer values.
byteOrder = binary.LittleEndian
// bucketIndexPrefix is the prefix used for all entries in the bucket
// index.
bucketIndexPrefix = []byte("bidx")
// curBucketIDKeyName is the name of the key used to keep track of the
// current bucket ID counter.
curBucketIDKeyName = []byte("bidx-cbid")
// metadataBucketID is the ID of the top-level metadata bucket.
// It is the value 0 encoded as an unsigned big-endian uint32.
metadataBucketID = [4]byte{}
// blockIdxBucketID is the ID of the internal block metadata bucket.
// It is the value 1 encoded as an unsigned big-endian uint32.
blockIdxBucketID = [4]byte{0x00, 0x00, 0x00, 0x01}
// blockIdxBucketName is the bucket used internally to track block
// metadata.
blockIdxBucketName = []byte("ffldb-blockidx")
// writeLocKeyName is the key used to store the current write file
// location.
writeLocKeyName = []byte("ffldb-writeloc")
)
// Common error strings.
const (
// errDbNotOpenStr is the text to use for the database.ErrDbNotOpen
// error code.
errDbNotOpenStr = "database is not open"
// errTxClosedStr is the text to use for the database.ErrTxClosed error
// code.
errTxClosedStr = "database tx is closed"
)
// bulkFetchData is allows a block location to be specified along with the
// index it was requested from. This in turn allows the bulk data loading
// functions to sort the data accesses based on the location to improve
// performance while keeping track of which result the data is for.
type bulkFetchData struct {
*blockLocation
replyIndex int
}
// bulkFetchDataSorter implements sort.Interface to allow a slice of
// bulkFetchData to be sorted. In particular it sorts by file and then
// offset so that reads from files are grouped and linear.
type bulkFetchDataSorter []bulkFetchData
// Len returns the number of items in the slice. It is part of the
// sort.Interface implementation.
func (s bulkFetchDataSorter) Len() int {
return len(s)
}
// Swap swaps the items at the passed indices. It is part of the
// sort.Interface implementation.
func (s bulkFetchDataSorter) Swap(i, j int) {
s[i], s[j] = s[j], s[i]
}
// Less returns whether the item with index i should sort before the item with
// index j. It is part of the sort.Interface implementation.
func (s bulkFetchDataSorter) Less(i, j int) bool {
if s[i].blockFileNum < s[j].blockFileNum {
return true
}
if s[i].blockFileNum > s[j].blockFileNum {
return false
}
return s[i].fileOffset < s[j].fileOffset
}
// makeDbErr creates a database.Error given a set of arguments.
func makeDbErr(c database.ErrorCode, desc string, err error) database.Error {
return database.Error{ErrorCode: c, Description: desc, Err: err}
}
// convertErr converts the passed leveldb error into a database error with an
// equivalent error code and the passed description. It also sets the passed
// error as the underlying error.
func convertErr(desc string, ldbErr error) database.Error {
// Use the driver-specific error code by default. The code below will
// update this with the converted error if it's recognized.
var code = database.ErrDriverSpecific
switch {
// Database corruption errors.
case ldberrors.IsCorrupted(ldbErr):
code = database.ErrCorruption
// Database open/create errors.
case ldbErr == leveldb.ErrClosed:
code = database.ErrDbNotOpen
// Transaction errors.
case ldbErr == leveldb.ErrSnapshotReleased:
code = database.ErrTxClosed
case ldbErr == leveldb.ErrIterReleased:
code = database.ErrTxClosed
}
return database.Error{ErrorCode: code, Description: desc, Err: ldbErr}
}
// copySlice returns a copy of the passed slice. This is mostly used to copy
// leveldb iterator keys and values since they are only valid until the iterator
// is moved instead of during the entirety of the transaction.
func copySlice(slice []byte) []byte {
ret := make([]byte, len(slice))
copy(ret, slice)
return ret
}
// cursor is an internal type used to represent a cursor over key/value pairs
// and nested buckets of a bucket and implements the database.Cursor interface.
type cursor struct {
bucket *bucket
dbIter iterator.Iterator
pendingIter iterator.Iterator
currentIter iterator.Iterator
}
// Enforce cursor implements the database.Cursor interface.
var _ database.Cursor = (*cursor)(nil)
// Bucket returns the bucket the cursor was created for.
//
// This function is part of the database.Cursor interface implementation.
func (c *cursor) Bucket() database.Bucket {
// Ensure transaction state is valid.
if err := c.bucket.tx.checkClosed(); err != nil {
return nil
}
return c.bucket
}
// Delete removes the current key/value pair the cursor is at without
// invalidating the cursor.
//
// Returns the following errors as required by the interface contract:
// - ErrIncompatibleValue if attempted when the cursor points to a nested
// bucket
// - ErrTxNotWritable if attempted against a read-only transaction
// - ErrTxClosed if the transaction has already been closed
//
// This function is part of the database.Cursor interface implementation.
func (c *cursor) Delete() error {
// Ensure transaction state is valid.
if err := c.bucket.tx.checkClosed(); err != nil {
return err
}
// Error if the cursor is exhausted.
if c.currentIter == nil {
str := "cursor is exhausted"
return makeDbErr(database.ErrIncompatibleValue, str, nil)
}
// Do not allow buckets to be deleted via the cursor.
key := c.currentIter.Key()
if bytes.HasPrefix(key, bucketIndexPrefix) {
str := "buckets may not be deleted from a cursor"
return makeDbErr(database.ErrIncompatibleValue, str, nil)
}
c.bucket.tx.deleteKey(copySlice(key), true)
return nil
}
// skipPendingUpdates skips any keys at the current database iterator position
// that are being updated by the transaction. The forwards flag indicates the
// direction the cursor is moving.
func (c *cursor) skipPendingUpdates(forwards bool) {
for c.dbIter.Valid() {
var skip bool
key := c.dbIter.Key()
if c.bucket.tx.pendingRemove.Has(key) {
skip = true
} else if c.bucket.tx.pendingKeys.Has(key) {
skip = true
}
if !skip {
break
}
if forwards {
c.dbIter.Next()
} else {
c.dbIter.Prev()
}
}
}
// chooseIterator first skips any entries in the database iterator that are
// being updated by the transaction and sets the current iterator to the
// appropriate iterator depending on their validity and the order they compare
// in while taking into account the direction flag. When the cursor is being
// moved forwards and both iterators are valid, the iterator with the smaller
// key is chosen and vice versa when the cursor is being moved backwards.
func (c *cursor) chooseIterator(forwards bool) bool {
// Skip any keys at the current database iterator position that are
// being updated by the transaction.
c.skipPendingUpdates(forwards)
// When both iterators are exhausted, the cursor is exhausted too.
if !c.dbIter.Valid() && !c.pendingIter.Valid() {
c.currentIter = nil
return false
}
// Choose the database iterator when the pending keys iterator is
// exhausted.
if !c.pendingIter.Valid() {
c.currentIter = c.dbIter
return true
}
// Choose the pending keys iterator when the database iterator is
// exhausted.
if !c.dbIter.Valid() {
c.currentIter = c.pendingIter
return true
}
// Both iterators are valid, so choose the iterator with either the
// smaller or larger key depending on the forwards flag.
compare := bytes.Compare(c.dbIter.Key(), c.pendingIter.Key())
if (forwards && compare > 0) || (!forwards && compare < 0) {
c.currentIter = c.pendingIter
} else {
c.currentIter = c.dbIter
}
return true
}
// First positions the cursor at the first key/value pair and returns whether or
// not the pair exists.
//
// This function is part of the database.Cursor interface implementation.
func (c *cursor) First() bool {
// Ensure transaction state is valid.
if err := c.bucket.tx.checkClosed(); err != nil {
return false
}
// Seek to the first key in both the database and pending iterators and
// choose the iterator that is both valid and has the smaller key.
c.dbIter.First()
c.pendingIter.First()
return c.chooseIterator(true)
}
// Last positions the cursor at the last key/value pair and returns whether or
// not the pair exists.
//
// This function is part of the database.Cursor interface implementation.
func (c *cursor) Last() bool {
// Ensure transaction state is valid.
if err := c.bucket.tx.checkClosed(); err != nil {
return false
}
// Seek to the last key in both the database and pending iterators and
// choose the iterator that is both valid and has the larger key.
c.dbIter.Last()
c.pendingIter.Last()
return c.chooseIterator(false)
}
// Next moves the cursor one key/value pair forward and returns whether or not
// the pair exists.
//
// This function is part of the database.Cursor interface implementation.
func (c *cursor) Next() bool {
// Ensure transaction state is valid.
if err := c.bucket.tx.checkClosed(); err != nil {
return false
}
// Nothing to return if cursor is exhausted.
if c.currentIter == nil {
return false
}
// Move the current iterator to the next entry and choose the iterator
// that is both valid and has the smaller key.
c.currentIter.Next()
return c.chooseIterator(true)
}
// Prev moves the cursor one key/value pair backward and returns whether or not
// the pair exists.
//
// This function is part of the database.Cursor interface implementation.
func (c *cursor) Prev() bool {
// Ensure transaction state is valid.
if err := c.bucket.tx.checkClosed(); err != nil {
return false
}
// Nothing to return if cursor is exhausted.
if c.currentIter == nil {
return false
}
// Move the current iterator to the previous entry and choose the
// iterator that is both valid and has the larger key.
c.currentIter.Prev()
return c.chooseIterator(false)
}
// Seek positions the cursor at the first key/value pair that is greater than or
// equal to the passed seek key. Returns false if no suitable key was found.
//
// This function is part of the database.Cursor interface implementation.
func (c *cursor) Seek(seek []byte) bool {
// Ensure transaction state is valid.
if err := c.bucket.tx.checkClosed(); err != nil {
return false
}
// Seek to the provided key in both the database and pending iterators
// then choose the iterator that is both valid and has the larger key.
seekKey := bucketizedKey(c.bucket.id, seek)
c.dbIter.Seek(seekKey)
c.pendingIter.Seek(seekKey)
return c.chooseIterator(true)
}
// rawKey returns the current key the cursor is pointing to without stripping
// the current bucket prefix or bucket index prefix.
func (c *cursor) rawKey() []byte {
// Nothing to return if cursor is exhausted.
if c.currentIter == nil {
return nil
}
return copySlice(c.currentIter.Key())
}
// Key returns the current key the cursor is pointing to.
//
// This function is part of the database.Cursor interface implementation.
func (c *cursor) Key() []byte {
// Ensure transaction state is valid.
if err := c.bucket.tx.checkClosed(); err != nil {
return nil
}
// Nothing to return if cursor is exhausted.
if c.currentIter == nil {
return nil
}
// Slice out the actual key name and make a copy since it is no longer
// valid after iterating to the next item.
//
// The key is after the bucket index prefix and parent ID when the
// cursor is pointing to a nested bucket.
key := c.currentIter.Key()
if bytes.HasPrefix(key, bucketIndexPrefix) {
key = key[len(bucketIndexPrefix)+4:]
return copySlice(key)
}
// The key is after the bucket ID when the cursor is pointing to a
// normal entry.
key = key[len(c.bucket.id):]
return copySlice(key)
}
// rawValue returns the current value the cursor is pointing to without
// stripping without filtering bucket index values.
func (c *cursor) rawValue() []byte {
// Nothing to return if cursor is exhausted.
if c.currentIter == nil {
return nil
}
return copySlice(c.currentIter.Value())
}
// Value returns the current value the cursor is pointing to. This will be nil
// for nested buckets.
//
// This function is part of the database.Cursor interface implementation.
func (c *cursor) Value() []byte {
// Ensure transaction state is valid.
if err := c.bucket.tx.checkClosed(); err != nil {
return nil
}
// Nothing to return if cursor is exhausted.
if c.currentIter == nil {
return nil
}
// Return nil for the value when the cursor is pointing to a nested
// bucket.
if bytes.HasPrefix(c.currentIter.Key(), bucketIndexPrefix) {
return nil
}
return copySlice(c.currentIter.Value())
}
// cursorType defines the type of cursor to create.
type cursorType int
// The following constants define the allowed cursor types.
const (
// ctKeys iterates through all of the keys in a given bucket.
ctKeys cursorType = iota
// ctBuckets iterates through all directly nested buckets in a given
// bucket.
ctBuckets
// ctFull iterates through both the keys and the directly nested buckets
// in a given bucket.
ctFull
)
// cursorFinalizer is either invoked when a cursor is being garbage collected or
// called manually to ensure the underlying cursor iterators are released.
func cursorFinalizer(c *cursor) {
c.dbIter.Release()
c.pendingIter.Release()
}
// newCursor returns a new cursor for the given bucket, bucket ID, and cursor
// type.
//
// NOTE: The caller is responsible for calling the cursorFinalizer function on
// the returned cursor.
func newCursor(b *bucket, bucketID []byte, cursorTyp cursorType) *cursor {
var dbIter, pendingIter iterator.Iterator
switch cursorTyp {
case ctKeys:
keyRange := util.BytesPrefix(bucketID)
dbIter = b.tx.snapshot.NewIterator(keyRange)
pendingKeyIter := newLdbTreapIter(b.tx, keyRange)
pendingIter = pendingKeyIter
case ctBuckets:
// The serialized bucket index key format is:
// <bucketindexprefix><parentbucketid><bucketname>
// Create an iterator for the both the database and the pending
// keys which are prefixed by the bucket index identifier and
// the provided bucket ID.
prefix := make([]byte, len(bucketIndexPrefix)+4)
copy(prefix, bucketIndexPrefix)
copy(prefix[len(bucketIndexPrefix):], bucketID)
bucketRange := util.BytesPrefix(prefix)
dbIter = b.tx.snapshot.NewIterator(bucketRange)
pendingBucketIter := newLdbTreapIter(b.tx, bucketRange)
pendingIter = pendingBucketIter
case ctFull:
fallthrough
default:
// The serialized bucket index key format is:
// <bucketindexprefix><parentbucketid><bucketname>
prefix := make([]byte, len(bucketIndexPrefix)+4)
copy(prefix, bucketIndexPrefix)
copy(prefix[len(bucketIndexPrefix):], bucketID)
bucketRange := util.BytesPrefix(prefix)
keyRange := util.BytesPrefix(bucketID)
// Since both keys and buckets are needed from the database,
// create an individual iterator for each prefix and then create
// a merged iterator from them.
dbKeyIter := b.tx.snapshot.NewIterator(keyRange)
dbBucketIter := b.tx.snapshot.NewIterator(bucketRange)
iters := []iterator.Iterator{dbKeyIter, dbBucketIter}
dbIter = iterator.NewMergedIterator(iters,
comparer.DefaultComparer, true)
// Since both keys and buckets are needed from the pending keys,
// create an individual iterator for each prefix and then create
// a merged iterator from them.
pendingKeyIter := newLdbTreapIter(b.tx, keyRange)
pendingBucketIter := newLdbTreapIter(b.tx, bucketRange)
iters = []iterator.Iterator{pendingKeyIter, pendingBucketIter}
pendingIter = iterator.NewMergedIterator(iters,
comparer.DefaultComparer, true)
}
// Create the cursor using the iterators.
return &cursor{bucket: b, dbIter: dbIter, pendingIter: pendingIter}
}
// bucket is an internal type used to represent a collection of key/value pairs
// and implements the database.Bucket interface.
type bucket struct {
tx *transaction
id [4]byte
}
// Enforce bucket implements the database.Bucket interface.
var _ database.Bucket = (*bucket)(nil)
// bucketIndexKey returns the actual key to use for storing and retrieving a
// child bucket in the bucket index. This is required because additional
// information is needed to distinguish nested buckets with the same name.
func bucketIndexKey(parentID [4]byte, key []byte) []byte {
// The serialized bucket index key format is:
// <bucketindexprefix><parentbucketid><bucketname>
indexKey := make([]byte, len(bucketIndexPrefix)+4+len(key))
copy(indexKey, bucketIndexPrefix)
copy(indexKey[len(bucketIndexPrefix):], parentID[:])
copy(indexKey[len(bucketIndexPrefix)+4:], key)
return indexKey
}
// bucketizedKey returns the actual key to use for storing and retrieving a key
// for the provided bucket ID. This is required because bucketizing is handled
// through the use of a unique prefix per bucket.
func bucketizedKey(bucketID [4]byte, key []byte) []byte {
// The serialized block index key format is:
// <bucketid><key>
bKey := make([]byte, 4+len(key))
copy(bKey, bucketID[:])
copy(bKey[4:], key)
return bKey
}
// Bucket retrieves a nested bucket with the given key. Returns nil if
// the bucket does not exist.
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) Bucket(key []byte) database.Bucket {
// Ensure transaction state is valid.
if err := b.tx.checkClosed(); err != nil {
return nil
}
// Attempt to fetch the ID for the child bucket. The bucket does not
// exist if the bucket index entry does not exist.
childID := b.tx.fetchKey(bucketIndexKey(b.id, key))
if childID == nil {
return nil
}
childBucket := &bucket{tx: b.tx}
copy(childBucket.id[:], childID)
return childBucket
}
// CreateBucket creates and returns a new nested bucket with the given key.
//
// Returns the following errors as required by the interface contract:
// - ErrBucketExists if the bucket already exists
// - ErrBucketNameRequired if the key is empty
// - ErrIncompatibleValue if the key is otherwise invalid for the particular
// implementation
// - ErrTxNotWritable if attempted against a read-only transaction
// - ErrTxClosed if the transaction has already been closed
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) CreateBucket(key []byte) (database.Bucket, error) {
// Ensure transaction state is valid.
if err := b.tx.checkClosed(); err != nil {
return nil, err
}
// Ensure the transaction is writable.
if !b.tx.writable {
str := "create bucket requires a writable database transaction"
return nil, makeDbErr(database.ErrTxNotWritable, str, nil)
}
// Ensure a key was provided.
if len(key) == 0 {
str := "create bucket requires a key"
return nil, makeDbErr(database.ErrBucketNameRequired, str, nil)
}
// Ensure bucket does not already exist.
bidxKey := bucketIndexKey(b.id, key)
if b.tx.hasKey(bidxKey) {
str := "bucket already exists"
return nil, makeDbErr(database.ErrBucketExists, str, nil)
}
// Find the appropriate next bucket ID to use for the new bucket. In
// the case of the special internal block index, keep the fixed ID.
var childID [4]byte
if b.id == metadataBucketID && bytes.Equal(key, blockIdxBucketName) {
childID = blockIdxBucketID
} else {
var err error
childID, err = b.tx.nextBucketID()
if err != nil {
return nil, err
}
}
// Add the new bucket to the bucket index.
if err := b.tx.putKey(bidxKey, childID[:]); err != nil {
str := fmt.Sprintf("failed to create bucket with key %q", key)
return nil, convertErr(str, err)
}
return &bucket{tx: b.tx, id: childID}, nil
}
// CreateBucketIfNotExists creates and returns a new nested bucket with the
// given key if it does not already exist.
//
// Returns the following errors as required by the interface contract:
// - ErrBucketNameRequired if the key is empty
// - ErrIncompatibleValue if the key is otherwise invalid for the particular
// implementation
// - ErrTxNotWritable if attempted against a read-only transaction
// - ErrTxClosed if the transaction has already been closed
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) CreateBucketIfNotExists(key []byte) (database.Bucket, error) {
// Ensure transaction state is valid.
if err := b.tx.checkClosed(); err != nil {
return nil, err
}
// Ensure the transaction is writable.
if !b.tx.writable {
str := "create bucket requires a writable database transaction"
return nil, makeDbErr(database.ErrTxNotWritable, str, nil)
}
// Return existing bucket if it already exists, otherwise create it.
if bucket := b.Bucket(key); bucket != nil {
return bucket, nil
}
return b.CreateBucket(key)
}
// DeleteBucket removes a nested bucket with the given key.
//
// Returns the following errors as required by the interface contract:
// - ErrBucketNotFound if the specified bucket does not exist
// - ErrTxNotWritable if attempted against a read-only transaction
// - ErrTxClosed if the transaction has already been closed
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) DeleteBucket(key []byte) error {
// Ensure transaction state is valid.
if err := b.tx.checkClosed(); err != nil {
return err
}
// Ensure the transaction is writable.
if !b.tx.writable {
str := "delete bucket requires a writable database transaction"
return makeDbErr(database.ErrTxNotWritable, str, nil)
}
// Attempt to fetch the ID for the child bucket. The bucket does not
// exist if the bucket index entry does not exist. In the case of the
// special internal block index, keep the fixed ID.
bidxKey := bucketIndexKey(b.id, key)
childID := b.tx.fetchKey(bidxKey)
if childID == nil {
str := fmt.Sprintf("bucket %q does not exist", key)
return makeDbErr(database.ErrBucketNotFound, str, nil)
}
// Remove all nested buckets and their keys.
childIDs := [][]byte{childID}
for len(childIDs) > 0 {
childID = childIDs[len(childIDs)-1]
childIDs = childIDs[:len(childIDs)-1]
// Delete all keys in the nested bucket.
keyCursor := newCursor(b, childID, ctKeys)
for ok := keyCursor.First(); ok; ok = keyCursor.Next() {
b.tx.deleteKey(keyCursor.rawKey(), false)
}
cursorFinalizer(keyCursor)
// Iterate through all nested buckets.
bucketCursor := newCursor(b, childID, ctBuckets)
for ok := bucketCursor.First(); ok; ok = bucketCursor.Next() {
// Push the id of the nested bucket onto the stack for
// the next iteration.
childID := bucketCursor.rawValue()
childIDs = append(childIDs, childID)
// Remove the nested bucket from the bucket index.
b.tx.deleteKey(bucketCursor.rawKey(), false)
}
cursorFinalizer(bucketCursor)
}
// Remove the nested bucket from the bucket index. Any buckets nested
// under it were already removed above.
b.tx.deleteKey(bidxKey, true)
return nil
}
// Cursor returns a new cursor, allowing for iteration over the bucket's
// key/value pairs and nested buckets in forward or backward order.
//
// You must seek to a position using the First, Last, or Seek functions before
// calling the Next, Prev, Key, or Value functions. Failure to do so will
// result in the same return values as an exhausted cursor, which is false for
// the Prev and Next functions and nil for Key and Value functions.
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) Cursor() database.Cursor {
// Ensure transaction state is valid.
if err := b.tx.checkClosed(); err != nil {
return &cursor{bucket: b}
}
// Create the cursor and setup a runtime finalizer to ensure the
// iterators are released when the cursor is garbage collected.
c := newCursor(b, b.id[:], ctFull)
runtime.SetFinalizer(c, cursorFinalizer)
return c
}
// ForEach invokes the passed function with every key/value pair in the bucket.
// This does not include nested buckets or the key/value pairs within those
// nested buckets.
//
// WARNING: It is not safe to mutate data while iterating with this method.
// Doing so may cause the underlying cursor to be invalidated and return
// unexpected keys and/or values.
//
// Returns the following errors as required by the interface contract:
// - ErrTxClosed if the transaction has already been closed
//
// NOTE: The values returned by this function are only valid during a
// transaction. Attempting to access them after a transaction has ended will
// likely result in an access violation.
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) ForEach(fn func(k, v []byte) error) error {
// Ensure transaction state is valid.
if err := b.tx.checkClosed(); err != nil {
return err
}
// Invoke the callback for each cursor item. Return the error returned
// from the callback when it is non-nil.
c := newCursor(b, b.id[:], ctKeys)
defer cursorFinalizer(c)
for ok := c.First(); ok; ok = c.Next() {
err := fn(c.Key(), c.Value())
if err != nil {
return err
}
}
return nil
}
// ForEachBucket invokes the passed function with the key of every nested bucket
// in the current bucket. This does not include any nested buckets within those
// nested buckets.
//
// WARNING: It is not safe to mutate data while iterating with this method.
// Doing so may cause the underlying cursor to be invalidated and return
// unexpected keys.
//
// Returns the following errors as required by the interface contract:
// - ErrTxClosed if the transaction has already been closed
//
// NOTE: The values returned by this function are only valid during a
// transaction. Attempting to access them after a transaction has ended will
// likely result in an access violation.
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) ForEachBucket(fn func(k []byte) error) error {
// Ensure transaction state is valid.
if err := b.tx.checkClosed(); err != nil {
return err
}
// Invoke the callback for each cursor item. Return the error returned
// from the callback when it is non-nil.
c := newCursor(b, b.id[:], ctBuckets)
defer cursorFinalizer(c)
for ok := c.First(); ok; ok = c.Next() {
err := fn(c.Key())
if err != nil {
return err
}
}
return nil
}
// Writable returns whether or not the bucket is writable.
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) Writable() bool {
return b.tx.writable
}
// Put saves the specified key/value pair to the bucket. Keys that do not
// already exist are added and keys that already exist are overwritten.
//
// Returns the following errors as required by the interface contract:
// - ErrKeyRequired if the key is empty
// - ErrIncompatibleValue if the key is the same as an existing bucket
// - ErrTxNotWritable if attempted against a read-only transaction
// - ErrTxClosed if the transaction has already been closed
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) Put(key, value []byte) error {
// Ensure transaction state is valid.
if err := b.tx.checkClosed(); err != nil {
return err
}
// Ensure the transaction is writable.
if !b.tx.writable {
str := "setting a key requires a writable database transaction"
return makeDbErr(database.ErrTxNotWritable, str, nil)
}
// Ensure a key was provided.
if len(key) == 0 {
str := "put requires a key"
return makeDbErr(database.ErrKeyRequired, str, nil)
}
return b.tx.putKey(bucketizedKey(b.id, key), value)
}
// Get returns the value for the given key. Returns nil if the key does not
// exist in this bucket. An empty slice is returned for keys that exist but
// have no value assigned.
//
// NOTE: The value returned by this function is only valid during a transaction.
// Attempting to access it after a transaction has ended results in undefined
// behavior. Additionally, the value must NOT be modified by the caller.
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) Get(key []byte) []byte {
// Ensure transaction state is valid.
if err := b.tx.checkClosed(); err != nil {
return nil
}
// Nothing to return if there is no key.
if len(key) == 0 {
return nil
}
return b.tx.fetchKey(bucketizedKey(b.id, key))
}
// Delete removes the specified key from the bucket. Deleting a key that does
// not exist does not return an error.
//
// Returns the following errors as required by the interface contract:
// - ErrKeyRequired if the key is empty
// - ErrIncompatibleValue if the key is the same as an existing bucket
// - ErrTxNotWritable if attempted against a read-only transaction
// - ErrTxClosed if the transaction has already been closed
//
// This function is part of the database.Bucket interface implementation.
func (b *bucket) Delete(key []byte) error {
// Ensure transaction state is valid.
if err := b.tx.checkClosed(); err != nil {
return err
}
// Ensure the transaction is writable.
if !b.tx.writable {
str := "deleting a value requires a writable database transaction"
return makeDbErr(database.ErrTxNotWritable, str, nil)
}
// Nothing to do if there is no key.
if len(key) == 0 {
return nil
}
b.tx.deleteKey(bucketizedKey(b.id, key), true)
return nil
}
// pendingBlock houses a block that will be written to disk when the database
// transaction is committed.
type pendingBlock struct {
hash *hash.Hash
bytes []byte
}
// transaction represents a database transaction. It can either be read-only or
// read-write and implements the database.Bucket interface. The transaction
// provides a root bucket against which all read and writes occur.
type transaction struct {
managed bool // Is the transaction managed?
closed bool // Is the transaction closed?
writable bool // Is the transaction writable?
db *db // DB instance the tx was created from.
snapshot *dbCacheSnapshot // Underlying snapshot for txns.
metaBucket *bucket // The root metadata bucket.
blockIdxBucket *bucket // The block index bucket.
// Blocks that need to be stored on commit. The pendingBlocks map is
// kept to allow quick lookups of pending data by block hash.
pendingBlocks map[hash.Hash]int
pendingBlockData []pendingBlock
// Keys that need to be stored or deleted on commit.
pendingKeys *treap.Mutable
pendingRemove *treap.Mutable
// Active iterators that need to be notified when the pending keys have
// been updated so the cursors can properly handle updates to the
// transaction state.
activeIterLock sync.RWMutex
activeIters []*treap.Iterator
}
// Enforce transaction implements the database.Tx interface.
var _ database.Tx = (*transaction)(nil)
// removeActiveIter removes the passed iterator from the list of active
// iterators against the pending keys treap.
func (tx *transaction) removeActiveIter(iter *treap.Iterator) {
// An indexing for loop is intentionally used over a range here as range
// does not reevaluate the slice on each iteration nor does it adjust
// the index for the modified slice.
tx.activeIterLock.Lock()
for i := 0; i < len(tx.activeIters); i++ {
if tx.activeIters[i] == iter {
copy(tx.activeIters[i:], tx.activeIters[i+1:])
tx.activeIters[len(tx.activeIters)-1] = nil
tx.activeIters = tx.activeIters[:len(tx.activeIters)-1]
}
}
tx.activeIterLock.Unlock()
}