diff options
Diffstat (limited to 'vendor/github.com/boltdb/bolt/tx.go')
| -rw-r--r-- | vendor/github.com/boltdb/bolt/tx.go | 684 |
1 files changed, 684 insertions, 0 deletions
diff --git a/vendor/github.com/boltdb/bolt/tx.go b/vendor/github.com/boltdb/bolt/tx.go new file mode 100644 index 000000000..6700308a2 --- /dev/null +++ b/vendor/github.com/boltdb/bolt/tx.go @@ -0,0 +1,684 @@ +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 +} |