gorush/vendor/github.com/dgraph-io/badger/table/table.go

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/*
* Copyright 2017 Dgraph Labs, Inc. and Contributors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package table
import (
"encoding/binary"
"fmt"
"os"
"path"
"path/filepath"
"strconv"
"strings"
"sync"
"sync/atomic"
"github.com/AndreasBriese/bbloom"
"github.com/dgraph-io/badger/options"
"github.com/dgraph-io/badger/y"
"github.com/pkg/errors"
)
const fileSuffix = ".sst"
type keyOffset struct {
key []byte
offset int
len int
}
// Table represents a loaded table file with the info we have about it
type Table struct {
sync.Mutex
fd *os.File // Own fd.
tableSize int // Initialized in OpenTable, using fd.Stat().
blockIndex []keyOffset
ref int32 // For file garbage collection. Atomic.
loadingMode options.FileLoadingMode
mmap []byte // Memory mapped.
// The following are initialized once and const.
smallest, biggest []byte // Smallest and largest keys.
id uint64 // file id, part of filename
bf bbloom.Bloom
}
// IncrRef increments the refcount (having to do with whether the file should be deleted)
func (t *Table) IncrRef() {
atomic.AddInt32(&t.ref, 1)
}
// DecrRef decrements the refcount and possibly deletes the table
func (t *Table) DecrRef() error {
newRef := atomic.AddInt32(&t.ref, -1)
if newRef == 0 {
// We can safely delete this file, because for all the current files, we always have
// at least one reference pointing to them.
// It's necessary to delete windows files
if t.loadingMode == options.MemoryMap {
y.Munmap(t.mmap)
}
if err := t.fd.Truncate(0); err != nil {
// This is very important to let the FS know that the file is deleted.
return err
}
filename := t.fd.Name()
if err := t.fd.Close(); err != nil {
return err
}
if err := os.Remove(filename); err != nil {
return err
}
}
return nil
}
type block struct {
offset int
data []byte
}
func (b block) NewIterator() *blockIterator {
return &blockIterator{data: b.data}
}
// OpenTable assumes file has only one table and opens it. Takes ownership of fd upon function
// entry. Returns a table with one reference count on it (decrementing which may delete the file!
// -- consider t.Close() instead). The fd has to writeable because we call Truncate on it before
// deleting.
func OpenTable(fd *os.File, loadingMode options.FileLoadingMode) (*Table, error) {
fileInfo, err := fd.Stat()
if err != nil {
// It's OK to ignore fd.Close() errs in this function because we have only read
// from the file.
_ = fd.Close()
return nil, y.Wrap(err)
}
filename := fileInfo.Name()
id, ok := ParseFileID(filename)
if !ok {
_ = fd.Close()
return nil, errors.Errorf("Invalid filename: %s", filename)
}
t := &Table{
fd: fd,
ref: 1, // Caller is given one reference.
id: id,
loadingMode: loadingMode,
}
t.tableSize = int(fileInfo.Size())
if loadingMode == options.MemoryMap {
t.mmap, err = y.Mmap(fd, false, fileInfo.Size())
if err != nil {
_ = fd.Close()
return nil, y.Wrapf(err, "Unable to map file")
}
} else if loadingMode == options.LoadToRAM {
err = t.loadToRAM()
if err != nil {
_ = fd.Close()
return nil, y.Wrap(err)
}
}
if err := t.readIndex(); err != nil {
return nil, y.Wrap(err)
}
it := t.NewIterator(false)
defer it.Close()
it.Rewind()
if it.Valid() {
t.smallest = it.Key()
}
it2 := t.NewIterator(true)
defer it2.Close()
it2.Rewind()
if it2.Valid() {
t.biggest = it2.Key()
}
return t, nil
}
// Close closes the open table. (Releases resources back to the OS.)
func (t *Table) Close() error {
if t.loadingMode == options.MemoryMap {
y.Munmap(t.mmap)
}
return t.fd.Close()
}
func (t *Table) read(off int, sz int) ([]byte, error) {
if len(t.mmap) > 0 {
if len(t.mmap[off:]) < sz {
return nil, y.ErrEOF
}
return t.mmap[off : off+sz], nil
}
res := make([]byte, sz)
nbr, err := t.fd.ReadAt(res, int64(off))
y.NumReads.Add(1)
y.NumBytesRead.Add(int64(nbr))
return res, err
}
func (t *Table) readNoFail(off int, sz int) []byte {
res, err := t.read(off, sz)
y.Check(err)
return res
}
func (t *Table) readIndex() error {
readPos := t.tableSize
// Read bloom filter.
readPos -= 4
buf := t.readNoFail(readPos, 4)
bloomLen := int(binary.BigEndian.Uint32(buf))
readPos -= bloomLen
data := t.readNoFail(readPos, bloomLen)
t.bf = bbloom.JSONUnmarshal(data)
readPos -= 4
buf = t.readNoFail(readPos, 4)
restartsLen := int(binary.BigEndian.Uint32(buf))
readPos -= 4 * restartsLen
buf = t.readNoFail(readPos, 4*restartsLen)
offsets := make([]int, restartsLen)
for i := 0; i < restartsLen; i++ {
offsets[i] = int(binary.BigEndian.Uint32(buf[:4]))
buf = buf[4:]
}
// The last offset stores the end of the last block.
for i := 0; i < len(offsets); i++ {
var o int
if i == 0 {
o = 0
} else {
o = offsets[i-1]
}
ko := keyOffset{
offset: o,
len: offsets[i] - o,
}
t.blockIndex = append(t.blockIndex, ko)
}
che := make(chan error, len(t.blockIndex))
blocks := make(chan int, len(t.blockIndex))
for i := 0; i < len(t.blockIndex); i++ {
blocks <- i
}
for i := 0; i < 64; i++ { // Run 64 goroutines.
go func() {
var h header
for index := range blocks {
ko := &t.blockIndex[index]
offset := ko.offset
buf, err := t.read(offset, h.Size())
if err != nil {
che <- errors.Wrap(err, "While reading first header in block")
continue
}
h.Decode(buf)
y.AssertTruef(h.plen == 0, "Key offset: %+v, h.plen = %d", *ko, h.plen)
offset += h.Size()
buf = make([]byte, h.klen)
var out []byte
if out, err = t.read(offset, int(h.klen)); err != nil {
che <- errors.Wrap(err, "While reading first key in block")
continue
}
y.AssertTrue(len(buf) == copy(buf, out))
ko.key = buf
che <- nil
}
}()
}
close(blocks) // to stop reading goroutines
var readError error
for i := 0; i < len(t.blockIndex); i++ {
if err := <-che; err != nil && readError == nil {
readError = err
}
}
if readError != nil {
return readError
}
return nil
}
func (t *Table) block(idx int) (block, error) {
y.AssertTruef(idx >= 0, "idx=%d", idx)
if idx >= len(t.blockIndex) {
return block{}, errors.New("block out of index")
}
ko := t.blockIndex[idx]
blk := block{
offset: ko.offset,
}
var err error
blk.data, err = t.read(blk.offset, ko.len)
return blk, err
}
// Size is its file size in bytes
func (t *Table) Size() int64 { return int64(t.tableSize) }
// Smallest is its smallest key, or nil if there are none
func (t *Table) Smallest() []byte { return t.smallest }
// Biggest is its biggest key, or nil if there are none
func (t *Table) Biggest() []byte { return t.biggest }
// Filename is NOT the file name. Just kidding, it is.
func (t *Table) Filename() string { return t.fd.Name() }
// ID is the table's ID number (used to make the file name).
func (t *Table) ID() uint64 { return t.id }
// DoesNotHave returns true if (but not "only if") the table does not have the key. It does a
// bloom filter lookup.
func (t *Table) DoesNotHave(key []byte) bool { return !t.bf.Has(key) }
// ParseFileID reads the file id out of a filename.
func ParseFileID(name string) (uint64, bool) {
name = path.Base(name)
if !strings.HasSuffix(name, fileSuffix) {
return 0, false
}
// suffix := name[len(fileSuffix):]
name = strings.TrimSuffix(name, fileSuffix)
id, err := strconv.Atoi(name)
if err != nil {
return 0, false
}
y.AssertTrue(id >= 0)
return uint64(id), true
}
// IDToFilename does the inverse of ParseFileID
func IDToFilename(id uint64) string {
return fmt.Sprintf("%06d", id) + fileSuffix
}
// NewFilename should be named TableFilepath -- it combines the dir with the ID to make a table
// filepath.
func NewFilename(id uint64, dir string) string {
return filepath.Join(dir, IDToFilename(id))
}
func (t *Table) loadToRAM() error {
t.mmap = make([]byte, t.tableSize)
read, err := t.fd.ReadAt(t.mmap, 0)
if err != nil || read != t.tableSize {
return y.Wrapf(err, "Unable to load file in memory. Table file: %s", t.Filename())
}
y.NumReads.Add(1)
y.NumBytesRead.Add(int64(read))
return nil
}