/usr/share/gocode/src/github.com/boltdb/bolt/tx.go is in golang-github-boltdb-bolt-dev 1.3.1-5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 | package bolt
import (
"fmt"
"io"
"os"
"sort"
"strings"
"time"
"unsafe"
)
// txid represents the internal transaction identifier.
type txid uint64
// Tx represents a read-only or read/write transaction on the database.
// Read-only transactions can be used for retrieving values for keys and creating cursors.
// Read/write transactions can create and remove buckets and create and remove keys.
//
// IMPORTANT: You must commit or rollback transactions when you are done with
// them. Pages can not be reclaimed by the writer until no more transactions
// are using them. A long running read transaction can cause the database to
// quickly grow.
type Tx struct {
writable bool
managed bool
db *DB
meta *meta
root Bucket
pages map[pgid]*page
stats TxStats
commitHandlers []func()
// WriteFlag specifies the flag for write-related methods like WriteTo().
// Tx opens the database file with the specified flag to copy the data.
//
// By default, the flag is unset, which works well for mostly in-memory
// workloads. For databases that are much larger than available RAM,
// set the flag to syscall.O_DIRECT to avoid trashing the page cache.
WriteFlag int
}
// init initializes the transaction.
func (tx *Tx) init(db *DB) {
tx.db = db
tx.pages = nil
// Copy the meta page since it can be changed by the writer.
tx.meta = &meta{}
db.meta().copy(tx.meta)
// Copy over the root bucket.
tx.root = newBucket(tx)
tx.root.bucket = &bucket{}
*tx.root.bucket = tx.meta.root
// Increment the transaction id and add a page cache for writable transactions.
if tx.writable {
tx.pages = make(map[pgid]*page)
tx.meta.txid += txid(1)
}
}
// ID returns the transaction id.
func (tx *Tx) ID() int {
return int(tx.meta.txid)
}
// DB returns a reference to the database that created the transaction.
func (tx *Tx) DB() *DB {
return tx.db
}
// Size returns current database size in bytes as seen by this transaction.
func (tx *Tx) Size() int64 {
return int64(tx.meta.pgid) * int64(tx.db.pageSize)
}
// Writable returns whether the transaction can perform write operations.
func (tx *Tx) Writable() bool {
return tx.writable
}
// Cursor creates a cursor associated with the root bucket.
// All items in the cursor will return a nil value because all root bucket keys point to buckets.
// The cursor is only valid as long as the transaction is open.
// Do not use a cursor after the transaction is closed.
func (tx *Tx) Cursor() *Cursor {
return tx.root.Cursor()
}
// Stats retrieves a copy of the current transaction statistics.
func (tx *Tx) Stats() TxStats {
return tx.stats
}
// Bucket retrieves a bucket by name.
// Returns nil if the bucket does not exist.
// The bucket instance is only valid for the lifetime of the transaction.
func (tx *Tx) Bucket(name []byte) *Bucket {
return tx.root.Bucket(name)
}
// CreateBucket creates a new bucket.
// Returns an error if the bucket already exists, if the bucket name is blank, or if the bucket name is too long.
// The bucket instance is only valid for the lifetime of the transaction.
func (tx *Tx) CreateBucket(name []byte) (*Bucket, error) {
return tx.root.CreateBucket(name)
}
// CreateBucketIfNotExists creates a new bucket if it doesn't already exist.
// Returns an error if the bucket name is blank, or if the bucket name is too long.
// The bucket instance is only valid for the lifetime of the transaction.
func (tx *Tx) CreateBucketIfNotExists(name []byte) (*Bucket, error) {
return tx.root.CreateBucketIfNotExists(name)
}
// DeleteBucket deletes a bucket.
// Returns an error if the bucket cannot be found or if the key represents a non-bucket value.
func (tx *Tx) DeleteBucket(name []byte) error {
return tx.root.DeleteBucket(name)
}
// ForEach executes a function for each bucket in the root.
// If the provided function returns an error then the iteration is stopped and
// the error is returned to the caller.
func (tx *Tx) ForEach(fn func(name []byte, b *Bucket) error) error {
return tx.root.ForEach(func(k, v []byte) error {
if err := fn(k, tx.root.Bucket(k)); err != nil {
return err
}
return nil
})
}
// OnCommit adds a handler function to be executed after the transaction successfully commits.
func (tx *Tx) OnCommit(fn func()) {
tx.commitHandlers = append(tx.commitHandlers, fn)
}
// Commit writes all changes to disk and updates the meta page.
// Returns an error if a disk write error occurs, or if Commit is
// called on a read-only transaction.
func (tx *Tx) Commit() error {
_assert(!tx.managed, "managed tx commit not allowed")
if tx.db == nil {
return ErrTxClosed
} else if !tx.writable {
return ErrTxNotWritable
}
// TODO(benbjohnson): Use vectorized I/O to write out dirty pages.
// Rebalance nodes which have had deletions.
var startTime = time.Now()
tx.root.rebalance()
if tx.stats.Rebalance > 0 {
tx.stats.RebalanceTime += time.Since(startTime)
}
// spill data onto dirty pages.
startTime = time.Now()
if err := tx.root.spill(); err != nil {
tx.rollback()
return err
}
tx.stats.SpillTime += time.Since(startTime)
// Free the old root bucket.
tx.meta.root.root = tx.root.root
opgid := tx.meta.pgid
// Free the freelist and allocate new pages for it. This will overestimate
// the size of the freelist but not underestimate the size (which would be bad).
tx.db.freelist.free(tx.meta.txid, tx.db.page(tx.meta.freelist))
p, err := tx.allocate((tx.db.freelist.size() / tx.db.pageSize) + 1)
if err != nil {
tx.rollback()
return err
}
if err := tx.db.freelist.write(p); err != nil {
tx.rollback()
return err
}
tx.meta.freelist = p.id
// If the high water mark has moved up then attempt to grow the database.
if tx.meta.pgid > opgid {
if err := tx.db.grow(int(tx.meta.pgid+1) * tx.db.pageSize); err != nil {
tx.rollback()
return err
}
}
// Write dirty pages to disk.
startTime = time.Now()
if err := tx.write(); err != nil {
tx.rollback()
return err
}
// If strict mode is enabled then perform a consistency check.
// Only the first consistency error is reported in the panic.
if tx.db.StrictMode {
ch := tx.Check()
var errs []string
for {
err, ok := <-ch
if !ok {
break
}
errs = append(errs, err.Error())
}
if len(errs) > 0 {
panic("check fail: " + strings.Join(errs, "\n"))
}
}
// Write meta to disk.
if err := tx.writeMeta(); err != nil {
tx.rollback()
return err
}
tx.stats.WriteTime += time.Since(startTime)
// Finalize the transaction.
tx.close()
// Execute commit handlers now that the locks have been removed.
for _, fn := range tx.commitHandlers {
fn()
}
return nil
}
// Rollback closes the transaction and ignores all previous updates. Read-only
// transactions must be rolled back and not committed.
func (tx *Tx) Rollback() error {
_assert(!tx.managed, "managed tx rollback not allowed")
if tx.db == nil {
return ErrTxClosed
}
tx.rollback()
return nil
}
func (tx *Tx) rollback() {
if tx.db == nil {
return
}
if tx.writable {
tx.db.freelist.rollback(tx.meta.txid)
tx.db.freelist.reload(tx.db.page(tx.db.meta().freelist))
}
tx.close()
}
func (tx *Tx) close() {
if tx.db == nil {
return
}
if tx.writable {
// Grab freelist stats.
var freelistFreeN = tx.db.freelist.free_count()
var freelistPendingN = tx.db.freelist.pending_count()
var freelistAlloc = tx.db.freelist.size()
// Remove transaction ref & writer lock.
tx.db.rwtx = nil
tx.db.rwlock.Unlock()
// Merge statistics.
tx.db.statlock.Lock()
tx.db.stats.FreePageN = freelistFreeN
tx.db.stats.PendingPageN = freelistPendingN
tx.db.stats.FreeAlloc = (freelistFreeN + freelistPendingN) * tx.db.pageSize
tx.db.stats.FreelistInuse = freelistAlloc
tx.db.stats.TxStats.add(&tx.stats)
tx.db.statlock.Unlock()
} else {
tx.db.removeTx(tx)
}
// Clear all references.
tx.db = nil
tx.meta = nil
tx.root = Bucket{tx: tx}
tx.pages = nil
}
// Copy writes the entire database to a writer.
// This function exists for backwards compatibility. Use WriteTo() instead.
func (tx *Tx) Copy(w io.Writer) error {
_, err := tx.WriteTo(w)
return err
}
// WriteTo writes the entire database to a writer.
// If err == nil then exactly tx.Size() bytes will be written into the writer.
func (tx *Tx) WriteTo(w io.Writer) (n int64, err error) {
// Attempt to open reader with WriteFlag
f, err := os.OpenFile(tx.db.path, os.O_RDONLY|tx.WriteFlag, 0)
if err != nil {
return 0, err
}
defer func() { _ = f.Close() }()
// Generate a meta page. We use the same page data for both meta pages.
buf := make([]byte, tx.db.pageSize)
page := (*page)(unsafe.Pointer(&buf[0]))
page.flags = metaPageFlag
*page.meta() = *tx.meta
// Write meta 0.
page.id = 0
page.meta().checksum = page.meta().sum64()
nn, err := w.Write(buf)
n += int64(nn)
if err != nil {
return n, fmt.Errorf("meta 0 copy: %s", err)
}
// Write meta 1 with a lower transaction id.
page.id = 1
page.meta().txid -= 1
page.meta().checksum = page.meta().sum64()
nn, err = w.Write(buf)
n += int64(nn)
if err != nil {
return n, fmt.Errorf("meta 1 copy: %s", err)
}
// Move past the meta pages in the file.
if _, err := f.Seek(int64(tx.db.pageSize*2), os.SEEK_SET); err != nil {
return n, fmt.Errorf("seek: %s", err)
}
// Copy data pages.
wn, err := io.CopyN(w, f, tx.Size()-int64(tx.db.pageSize*2))
n += wn
if err != nil {
return n, err
}
return n, f.Close()
}
// CopyFile copies the entire database to file at the given path.
// A reader transaction is maintained during the copy so it is safe to continue
// using the database while a copy is in progress.
func (tx *Tx) CopyFile(path string, mode os.FileMode) error {
f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, mode)
if err != nil {
return err
}
err = tx.Copy(f)
if err != nil {
_ = f.Close()
return err
}
return f.Close()
}
// Check performs several consistency checks on the database for this transaction.
// An error is returned if any inconsistency is found.
//
// It can be safely run concurrently on a writable transaction. However, this
// incurs a high cost for large databases and databases with a lot of subbuckets
// because of caching. This overhead can be removed if running on a read-only
// transaction, however, it is not safe to execute other writer transactions at
// the same time.
func (tx *Tx) Check() <-chan error {
ch := make(chan error)
go tx.check(ch)
return ch
}
func (tx *Tx) check(ch chan error) {
// Check if any pages are double freed.
freed := make(map[pgid]bool)
all := make([]pgid, tx.db.freelist.count())
tx.db.freelist.copyall(all)
for _, id := range all {
if freed[id] {
ch <- fmt.Errorf("page %d: already freed", id)
}
freed[id] = true
}
// Track every reachable page.
reachable := make(map[pgid]*page)
reachable[0] = tx.page(0) // meta0
reachable[1] = tx.page(1) // meta1
for i := uint32(0); i <= tx.page(tx.meta.freelist).overflow; i++ {
reachable[tx.meta.freelist+pgid(i)] = tx.page(tx.meta.freelist)
}
// Recursively check buckets.
tx.checkBucket(&tx.root, reachable, freed, ch)
// Ensure all pages below high water mark are either reachable or freed.
for i := pgid(0); i < tx.meta.pgid; i++ {
_, isReachable := reachable[i]
if !isReachable && !freed[i] {
ch <- fmt.Errorf("page %d: unreachable unfreed", int(i))
}
}
// Close the channel to signal completion.
close(ch)
}
func (tx *Tx) checkBucket(b *Bucket, reachable map[pgid]*page, freed map[pgid]bool, ch chan error) {
// Ignore inline buckets.
if b.root == 0 {
return
}
// Check every page used by this bucket.
b.tx.forEachPage(b.root, 0, func(p *page, _ int) {
if p.id > tx.meta.pgid {
ch <- fmt.Errorf("page %d: out of bounds: %d", int(p.id), int(b.tx.meta.pgid))
}
// Ensure each page is only referenced once.
for i := pgid(0); i <= pgid(p.overflow); i++ {
var id = p.id + i
if _, ok := reachable[id]; ok {
ch <- fmt.Errorf("page %d: multiple references", int(id))
}
reachable[id] = p
}
// We should only encounter un-freed leaf and branch pages.
if freed[p.id] {
ch <- fmt.Errorf("page %d: reachable freed", int(p.id))
} else if (p.flags&branchPageFlag) == 0 && (p.flags&leafPageFlag) == 0 {
ch <- fmt.Errorf("page %d: invalid type: %s", int(p.id), p.typ())
}
})
// Check each bucket within this bucket.
_ = b.ForEach(func(k, v []byte) error {
if child := b.Bucket(k); child != nil {
tx.checkBucket(child, reachable, freed, ch)
}
return nil
})
}
// allocate returns a contiguous block of memory starting at a given page.
func (tx *Tx) allocate(count int) (*page, error) {
p, err := tx.db.allocate(count)
if err != nil {
return nil, err
}
// Save to our page cache.
tx.pages[p.id] = p
// Update statistics.
tx.stats.PageCount++
tx.stats.PageAlloc += count * tx.db.pageSize
return p, nil
}
// write writes any dirty pages to disk.
func (tx *Tx) write() error {
// Sort pages by id.
pages := make(pages, 0, len(tx.pages))
for _, p := range tx.pages {
pages = append(pages, p)
}
// Clear out page cache early.
tx.pages = make(map[pgid]*page)
sort.Sort(pages)
// Write pages to disk in order.
for _, p := range pages {
size := (int(p.overflow) + 1) * tx.db.pageSize
offset := int64(p.id) * int64(tx.db.pageSize)
// Write out page in "max allocation" sized chunks.
ptr := (*[maxAllocSize]byte)(unsafe.Pointer(p))
for {
// Limit our write to our max allocation size.
sz := size
if sz > maxAllocSize-1 {
sz = maxAllocSize - 1
}
// Write chunk to disk.
buf := ptr[:sz]
if _, err := tx.db.ops.writeAt(buf, offset); err != nil {
return err
}
// Update statistics.
tx.stats.Write++
// Exit inner for loop if we've written all the chunks.
size -= sz
if size == 0 {
break
}
// Otherwise move offset forward and move pointer to next chunk.
offset += int64(sz)
ptr = (*[maxAllocSize]byte)(unsafe.Pointer(&ptr[sz]))
}
}
// Ignore file sync if flag is set on DB.
if !tx.db.NoSync || IgnoreNoSync {
if err := fdatasync(tx.db); err != nil {
return err
}
}
// Put small pages back to page pool.
for _, p := range pages {
// Ignore page sizes over 1 page.
// These are allocated using make() instead of the page pool.
if int(p.overflow) != 0 {
continue
}
buf := (*[maxAllocSize]byte)(unsafe.Pointer(p))[:tx.db.pageSize]
// See https://go.googlesource.com/go/+/f03c9202c43e0abb130669852082117ca50aa9b1
for i := range buf {
buf[i] = 0
}
tx.db.pagePool.Put(buf)
}
return nil
}
// writeMeta writes the meta to the disk.
func (tx *Tx) writeMeta() error {
// Create a temporary buffer for the meta page.
buf := make([]byte, tx.db.pageSize)
p := tx.db.pageInBuffer(buf, 0)
tx.meta.write(p)
// Write the meta page to file.
if _, err := tx.db.ops.writeAt(buf, int64(p.id)*int64(tx.db.pageSize)); err != nil {
return err
}
if !tx.db.NoSync || IgnoreNoSync {
if err := fdatasync(tx.db); err != nil {
return err
}
}
// Update statistics.
tx.stats.Write++
return nil
}
// page returns a reference to the page with a given id.
// If page has been written to then a temporary buffered page is returned.
func (tx *Tx) page(id pgid) *page {
// Check the dirty pages first.
if tx.pages != nil {
if p, ok := tx.pages[id]; ok {
return p
}
}
// Otherwise return directly from the mmap.
return tx.db.page(id)
}
// forEachPage iterates over every page within a given page and executes a function.
func (tx *Tx) forEachPage(pgid pgid, depth int, fn func(*page, int)) {
p := tx.page(pgid)
// Execute function.
fn(p, depth)
// Recursively loop over children.
if (p.flags & branchPageFlag) != 0 {
for i := 0; i < int(p.count); i++ {
elem := p.branchPageElement(uint16(i))
tx.forEachPage(elem.pgid, depth+1, fn)
}
}
}
// Page returns page information for a given page number.
// This is only safe for concurrent use when used by a writable transaction.
func (tx *Tx) Page(id int) (*PageInfo, error) {
if tx.db == nil {
return nil, ErrTxClosed
} else if pgid(id) >= tx.meta.pgid {
return nil, nil
}
// Build the page info.
p := tx.db.page(pgid(id))
info := &PageInfo{
ID: id,
Count: int(p.count),
OverflowCount: int(p.overflow),
}
// Determine the type (or if it's free).
if tx.db.freelist.freed(pgid(id)) {
info.Type = "free"
} else {
info.Type = p.typ()
}
return info, nil
}
// TxStats represents statistics about the actions performed by the transaction.
type TxStats struct {
// Page statistics.
PageCount int // number of page allocations
PageAlloc int // total bytes allocated
// Cursor statistics.
CursorCount int // number of cursors created
// Node statistics
NodeCount int // number of node allocations
NodeDeref int // number of node dereferences
// Rebalance statistics.
Rebalance int // number of node rebalances
RebalanceTime time.Duration // total time spent rebalancing
// Split/Spill statistics.
Split int // number of nodes split
Spill int // number of nodes spilled
SpillTime time.Duration // total time spent spilling
// Write statistics.
Write int // number of writes performed
WriteTime time.Duration // total time spent writing to disk
}
func (s *TxStats) add(other *TxStats) {
s.PageCount += other.PageCount
s.PageAlloc += other.PageAlloc
s.CursorCount += other.CursorCount
s.NodeCount += other.NodeCount
s.NodeDeref += other.NodeDeref
s.Rebalance += other.Rebalance
s.RebalanceTime += other.RebalanceTime
s.Split += other.Split
s.Spill += other.Spill
s.SpillTime += other.SpillTime
s.Write += other.Write
s.WriteTime += other.WriteTime
}
// Sub calculates and returns the difference between two sets of transaction stats.
// This is useful when obtaining stats at two different points and time and
// you need the performance counters that occurred within that time span.
func (s *TxStats) Sub(other *TxStats) TxStats {
var diff TxStats
diff.PageCount = s.PageCount - other.PageCount
diff.PageAlloc = s.PageAlloc - other.PageAlloc
diff.CursorCount = s.CursorCount - other.CursorCount
diff.NodeCount = s.NodeCount - other.NodeCount
diff.NodeDeref = s.NodeDeref - other.NodeDeref
diff.Rebalance = s.Rebalance - other.Rebalance
diff.RebalanceTime = s.RebalanceTime - other.RebalanceTime
diff.Split = s.Split - other.Split
diff.Spill = s.Spill - other.Spill
diff.SpillTime = s.SpillTime - other.SpillTime
diff.Write = s.Write - other.Write
diff.WriteTime = s.WriteTime - other.WriteTime
return diff
}
|