ceremonyclient/pebble/internal/manifest/version.go

1562 lines
56 KiB
Go
Raw Normal View History

2024-01-03 07:31:42 +00:00
// Copyright 2012 The LevelDB-Go and Pebble Authors. All rights reserved. Use
// of this source code is governed by a BSD-style license that can be found in
// the LICENSE file.
package manifest
import (
"bytes"
"fmt"
"sort"
"strconv"
"strings"
"sync"
"sync/atomic"
"unicode"
"github.com/cockroachdb/errors"
"github.com/cockroachdb/pebble/internal/base"
"github.com/cockroachdb/pebble/internal/invariants"
stdcmp "github.com/cockroachdb/pebble/shims/cmp"
)
// Compare exports the base.Compare type.
type Compare = base.Compare
// InternalKey exports the base.InternalKey type.
type InternalKey = base.InternalKey
// TableInfo contains the common information for table related events.
type TableInfo struct {
// FileNum is the internal DB identifier for the table.
FileNum base.FileNum
// Size is the size of the file in bytes.
Size uint64
// Smallest is the smallest internal key in the table.
Smallest InternalKey
// Largest is the largest internal key in the table.
Largest InternalKey
// SmallestSeqNum is the smallest sequence number in the table.
SmallestSeqNum uint64
// LargestSeqNum is the largest sequence number in the table.
LargestSeqNum uint64
}
// TableStats contains statistics on a table used for compaction heuristics,
// and export via Metrics.
type TableStats struct {
// The total number of entries in the table.
NumEntries uint64
// The number of point and range deletion entries in the table.
NumDeletions uint64
// NumRangeKeySets is the total number of range key sets in the table.
//
// NB: If there's a chance that the sstable contains any range key sets,
// then NumRangeKeySets must be > 0.
NumRangeKeySets uint64
// Estimate of the total disk space that may be dropped by this table's
// point deletions by compacting them.
PointDeletionsBytesEstimate uint64
// Estimate of the total disk space that may be dropped by this table's
// range deletions by compacting them. This estimate is at data-block
// granularity and is not updated if compactions beneath the table reduce
// the amount of reclaimable disk space. It also does not account for
// overlapping data in L0 and ignores L0 sublevels, but the error that
// introduces is expected to be small.
//
// Tables in the bottommost level of the LSM may have a nonzero estimate if
// snapshots or move compactions prevented the elision of their range
// tombstones. A table in the bottommost level that was ingested into L6
// will have a zero estimate, because the file's sequence numbers indicate
// that the tombstone cannot drop any data contained within the file itself.
RangeDeletionsBytesEstimate uint64
// Total size of value blocks and value index block.
ValueBlocksSize uint64
}
// boundType represents the type of key (point or range) present as the smallest
// and largest keys.
type boundType uint8
const (
boundTypePointKey boundType = iota + 1
boundTypeRangeKey
)
// CompactionState is the compaction state of a file.
//
// The following shows the valid state transitions:
//
// NotCompacting --> Compacting --> Compacted
// ^ |
// | |
// +-------<-------+
//
// Input files to a compaction transition to Compacting when a compaction is
// picked. A file that has finished compacting typically transitions into the
// Compacted state, at which point it is effectively obsolete ("zombied") and
// will eventually be removed from the LSM. A file that has been move-compacted
// will transition from Compacting back into the NotCompacting state, signaling
// that the file may be selected for a subsequent compaction. A failed
// compaction will result in all input tables transitioning from Compacting to
// NotCompacting.
//
// This state is in-memory only. It is not persisted to the manifest.
type CompactionState uint8
// CompactionStates.
const (
CompactionStateNotCompacting CompactionState = iota
CompactionStateCompacting
CompactionStateCompacted
)
// String implements fmt.Stringer.
func (s CompactionState) String() string {
switch s {
case CompactionStateNotCompacting:
return "NotCompacting"
case CompactionStateCompacting:
return "Compacting"
case CompactionStateCompacted:
return "Compacted"
default:
panic(fmt.Sprintf("pebble: unknown compaction state %d", s))
}
}
// FileMetadata is maintained for leveled-ssts, i.e., they belong to a level of
// some version. FileMetadata does not contain the actual level of the sst,
// since such leveled-ssts can move across levels in different versions, while
// sharing the same FileMetadata. There are two kinds of leveled-ssts, physical
// and virtual. Underlying both leveled-ssts is a backing-sst, for which the
// only state is FileBacking. A backing-sst is level-less. It is possible for a
// backing-sst to be referred to by a physical sst in one version and by one or
// more virtual ssts in one or more versions. A backing-sst becomes obsolete
// and can be deleted once it is no longer required by any physical or virtual
// sst in any version.
//
// We maintain some invariants:
//
// 1. Each physical and virtual sst will have a unique FileMetadata.FileNum,
// and there will be exactly one FileMetadata associated with the FileNum.
//
// 2. Within a version, a backing-sst is either only referred to by one
// physical sst or one or more virtual ssts.
//
// 3. Once a backing-sst is referred to by a virtual sst in the latest version,
// it cannot go back to being referred to by a physical sst in any future
// version.
//
// Once a physical sst is no longer needed by any version, we will no longer
// maintain the file metadata associated with it. We will still maintain the
// FileBacking associated with the physical sst if the backing sst is required
// by any virtual ssts in any version.
type FileMetadata struct {
// AllowedSeeks is used to determine if a file should be picked for
// a read triggered compaction. It is decremented when read sampling
// in pebble.Iterator after every after every positioning operation
// that returns a user key (eg. Next, Prev, SeekGE, SeekLT, etc).
AllowedSeeks atomic.Int64
// statsValid indicates if stats have been loaded for the table. The
// TableStats structure is populated only if valid is true.
statsValid atomic.Bool
// FileBacking is the state which backs either a physical or virtual
// sstables.
FileBacking *FileBacking
// InitAllowedSeeks is the inital value of allowed seeks. This is used
// to re-set allowed seeks on a file once it hits 0.
InitAllowedSeeks int64
// FileNum is the file number.
//
// INVARIANT: when !FileMetadata.Virtual, FileNum == FileBacking.DiskFileNum.
FileNum base.FileNum
// Size is the size of the file, in bytes. Size is an approximate value for
// virtual sstables.
//
// INVARIANTS:
// - When !FileMetadata.Virtual, Size == FileBacking.Size.
// - Size should be non-zero. Size 0 virtual sstables must not be created.
Size uint64
// File creation time in seconds since the epoch (1970-01-01 00:00:00
// UTC). For ingested sstables, this corresponds to the time the file was
// ingested. For virtual sstables, this corresponds to the wall clock time
// when the FileMetadata for the virtual sstable was first created.
CreationTime int64
// Lower and upper bounds for the smallest and largest sequence numbers in
// the table, across both point and range keys. For physical sstables, these
// values are tight bounds. For virtual sstables, there is no guarantee that
// there will be keys with SmallestSeqNum or LargestSeqNum within virtual
// sstable bounds.
SmallestSeqNum uint64
LargestSeqNum uint64
// SmallestPointKey and LargestPointKey are the inclusive bounds for the
// internal point keys stored in the table. This includes RANGEDELs, which
// alter point keys.
// NB: these field should be set using ExtendPointKeyBounds. They are left
// exported for reads as an optimization.
SmallestPointKey InternalKey
LargestPointKey InternalKey
// SmallestRangeKey and LargestRangeKey are the inclusive bounds for the
// internal range keys stored in the table.
// NB: these field should be set using ExtendRangeKeyBounds. They are left
// exported for reads as an optimization.
SmallestRangeKey InternalKey
LargestRangeKey InternalKey
// Smallest and Largest are the inclusive bounds for the internal keys stored
// in the table, across both point and range keys.
// NB: these fields are derived from their point and range key equivalents,
// and are updated via the MaybeExtend{Point,Range}KeyBounds methods.
Smallest InternalKey
Largest InternalKey
// Stats describe table statistics. Protected by DB.mu.
//
// For virtual sstables, set stats upon virtual sstable creation as
// asynchronous computation of stats is not currently supported.
//
// TODO(bananabrick): To support manifest replay for virtual sstables, we
// probably need to compute virtual sstable stats asynchronously. Otherwise,
// we'd have to write virtual sstable stats to the version edit.
Stats TableStats
// For L0 files only. Protected by DB.mu. Used to generate L0 sublevels and
// pick L0 compactions. Only accurate for the most recent Version.
SubLevel int
L0Index int
minIntervalIndex int
maxIntervalIndex int
// NB: the alignment of this struct is 8 bytes. We pack all the bools to
// ensure an optimal packing.
// IsIntraL0Compacting is set to True if this file is part of an intra-L0
// compaction. When it's true, IsCompacting must also return true. If
// Compacting is true and IsIntraL0Compacting is false for an L0 file, the
// file must be part of a compaction to Lbase.
IsIntraL0Compacting bool
CompactionState CompactionState
// True if compaction of this file has been explicitly requested.
// Previously, RocksDB and earlier versions of Pebble allowed this
// flag to be set by a user table property collector. Some earlier
// versions of Pebble respected this flag, while other more recent
// versions ignored this flag.
//
// More recently this flag has been repurposed to facilitate the
// compaction of 'atomic compaction units'. Files marked for
// compaction are compacted in a rewrite compaction at the lowest
// possible compaction priority.
//
// NB: A count of files marked for compaction is maintained on
// Version, and compaction picking reads cached annotations
// determined by this field.
//
// Protected by DB.mu.
MarkedForCompaction bool
// HasPointKeys tracks whether the table contains point keys (including
// RANGEDELs). If a table contains only range deletions, HasPointsKeys is
// still true.
HasPointKeys bool
// HasRangeKeys tracks whether the table contains any range keys.
HasRangeKeys bool
// smallestSet and largestSet track whether the overall bounds have been set.
boundsSet bool
// boundTypeSmallest and boundTypeLargest provide an indication as to which
// key type (point or range) corresponds to the smallest and largest overall
// table bounds.
boundTypeSmallest, boundTypeLargest boundType
// Virtual is true if the FileMetadata belongs to a virtual sstable.
Virtual bool
}
// PhysicalFileMeta is used by functions which want a guarantee that their input
// belongs to a physical sst and not a virtual sst.
//
// NB: This type should only be constructed by calling
// FileMetadata.PhysicalMeta.
type PhysicalFileMeta struct {
*FileMetadata
}
// VirtualFileMeta is used by functions which want a guarantee that their input
// belongs to a virtual sst and not a physical sst.
//
// A VirtualFileMeta inherits all the same fields as a FileMetadata. These
// fields have additional invariants imposed on them, and/or slightly varying
// meanings:
// - Smallest and Largest (and their counterparts
// {Smallest, Largest}{Point,Range}Key) remain tight bounds that represent a
// key at that exact bound. We make the effort to determine the next smallest
// or largest key in an sstable after virtualizing it, to maintain this
// tightness. If the largest is a sentinel key (IsExclusiveSentinel()), it
// could mean that a rangedel or range key ends at that user key, or has been
// truncated to that user key.
// - One invariant is that if a rangedel or range key is truncated on its
// upper bound, the virtual sstable *must* have a rangedel or range key
// sentinel key as its upper bound. This is because truncation yields
// an exclusive upper bound for the rangedel/rangekey, and if there are
// any points at that exclusive upper bound within the same virtual
// sstable, those could get uncovered by this truncation. We enforce this
// invariant in calls to keyspan.Truncate.
// - Size is an estimate of the size of the virtualized portion of this sstable.
// The underlying file's size is stored in FileBacking.Size, though it could
// also be estimated or could correspond to just the referenced portion of
// a file (eg. if the file originated on another node).
// - Size must be > 0.
// - SmallestSeqNum and LargestSeqNum are loose bounds for virtual sstables.
// This means that all keys in the virtual sstable must have seqnums within
// [SmallestSeqNum, LargestSeqNum], however there's no guarantee that there's
// a key with a seqnum at either of the bounds. Calculating tight seqnum
// bounds would be too expensive and deliver little value.
//
// NB: This type should only be constructed by calling FileMetadata.VirtualMeta.
type VirtualFileMeta struct {
*FileMetadata
}
// PhysicalMeta should be the only source of creating the PhysicalFileMeta
// wrapper type.
func (m *FileMetadata) PhysicalMeta() PhysicalFileMeta {
if m.Virtual {
panic("pebble: file metadata does not belong to a physical sstable")
}
return PhysicalFileMeta{
m,
}
}
// VirtualMeta should be the only source of creating the VirtualFileMeta wrapper
// type.
func (m *FileMetadata) VirtualMeta() VirtualFileMeta {
if !m.Virtual {
panic("pebble: file metadata does not belong to a virtual sstable")
}
return VirtualFileMeta{
m,
}
}
// FileBacking either backs a single physical sstable, or one or more virtual
// sstables.
//
// See the comment above the FileMetadata type for sstable terminology.
type FileBacking struct {
// Reference count for the backing file on disk: incremented when a
// physical or virtual sstable which is backed by the FileBacking is
// added to a version and decremented when the version is unreferenced.
// We ref count in order to determine when it is safe to delete a
// backing sst file from disk. The backing file is obsolete when the
// reference count falls to zero.
refs atomic.Int32
// latestVersionRefs are the references to the FileBacking in the
// latest version. This reference can be through a single physical
// sstable in the latest version, or one or more virtual sstables in the
// latest version.
//
// INVARIANT: latestVersionRefs <= refs.
latestVersionRefs atomic.Int32
// VirtualizedSize is set iff the backing sst is only referred to by
// virtual ssts in the latest version. VirtualizedSize is the sum of the
// virtual sstable sizes of all of the virtual sstables in the latest
// version which are backed by the physical sstable. When a virtual
// sstable is removed from the latest version, we will decrement the
// VirtualizedSize. During compaction picking, we'll compensate a
// virtual sstable file size by
// (FileBacking.Size - FileBacking.VirtualizedSize) / latestVersionRefs.
// The intuition is that if FileBacking.Size - FileBacking.VirtualizedSize
// is high, then the space amplification due to virtual sstables is
// high, and we should pick the virtual sstable with a higher priority.
//
// TODO(bananabrick): Compensate the virtual sstable file size using
// the VirtualizedSize during compaction picking and test.
VirtualizedSize atomic.Uint64
DiskFileNum base.DiskFileNum
Size uint64
}
// InitPhysicalBacking allocates and sets the FileBacking which is required by a
// physical sstable FileMetadata.
//
// Ensure that the state required by FileBacking, such as the FileNum, is
// already set on the FileMetadata before InitPhysicalBacking is called.
// Calling InitPhysicalBacking only after the relevant state has been set in the
// FileMetadata is not necessary in tests which don't rely on FileBacking.
func (m *FileMetadata) InitPhysicalBacking() {
if m.Virtual {
panic("pebble: virtual sstables should use a pre-existing FileBacking")
}
if m.FileBacking == nil {
m.FileBacking = &FileBacking{Size: m.Size, DiskFileNum: m.FileNum.DiskFileNum()}
}
}
// InitProviderBacking creates a new FileBacking for a file backed by
// an objstorage.Provider.
func (m *FileMetadata) InitProviderBacking(fileNum base.DiskFileNum) {
if !m.Virtual {
panic("pebble: provider-backed sstables must be virtual")
}
if m.FileBacking == nil {
m.FileBacking = &FileBacking{DiskFileNum: fileNum}
}
}
// ValidateVirtual should be called once the FileMetadata for a virtual sstable
// is created to verify that the fields of the virtual sstable are sound.
func (m *FileMetadata) ValidateVirtual(createdFrom *FileMetadata) {
if !m.Virtual {
panic("pebble: invalid virtual sstable")
}
if createdFrom.SmallestSeqNum != m.SmallestSeqNum {
panic("pebble: invalid smallest sequence number for virtual sstable")
}
if createdFrom.LargestSeqNum != m.LargestSeqNum {
panic("pebble: invalid largest sequence number for virtual sstable")
}
if createdFrom.FileBacking != nil && createdFrom.FileBacking != m.FileBacking {
panic("pebble: invalid physical sstable state for virtual sstable")
}
if m.Size == 0 {
panic("pebble: virtual sstable size must be set upon creation")
}
}
// Refs returns the refcount of backing sstable.
func (m *FileMetadata) Refs() int32 {
return m.FileBacking.refs.Load()
}
// Ref increments the ref count associated with the backing sstable.
func (m *FileMetadata) Ref() {
m.FileBacking.refs.Add(1)
}
// Unref decrements the ref count associated with the backing sstable.
func (m *FileMetadata) Unref() int32 {
v := m.FileBacking.refs.Add(-1)
if invariants.Enabled && v < 0 {
panic("pebble: invalid FileMetadata refcounting")
}
return v
}
// LatestRef increments the latest ref count associated with the backing
// sstable.
func (m *FileMetadata) LatestRef() {
m.FileBacking.latestVersionRefs.Add(1)
if m.Virtual {
m.FileBacking.VirtualizedSize.Add(m.Size)
}
}
// LatestUnref decrements the latest ref count associated with the backing
// sstable.
func (m *FileMetadata) LatestUnref() int32 {
if m.Virtual {
m.FileBacking.VirtualizedSize.Add(-m.Size)
}
v := m.FileBacking.latestVersionRefs.Add(-1)
if invariants.Enabled && v < 0 {
panic("pebble: invalid FileMetadata latest refcounting")
}
return v
}
// LatestRefs returns the latest ref count associated with the backing sstable.
func (m *FileMetadata) LatestRefs() int32 {
return m.FileBacking.latestVersionRefs.Load()
}
// SetCompactionState transitions this file's compaction state to the given
// state. Protected by DB.mu.
func (m *FileMetadata) SetCompactionState(to CompactionState) {
if invariants.Enabled {
transitionErr := func() error {
return errors.Newf("pebble: invalid compaction state transition: %s -> %s", m.CompactionState, to)
}
switch m.CompactionState {
case CompactionStateNotCompacting:
if to != CompactionStateCompacting {
panic(transitionErr())
}
case CompactionStateCompacting:
if to != CompactionStateCompacted && to != CompactionStateNotCompacting {
panic(transitionErr())
}
case CompactionStateCompacted:
panic(transitionErr())
default:
panic(fmt.Sprintf("pebble: unknown compaction state: %d", m.CompactionState))
}
}
m.CompactionState = to
}
// IsCompacting returns true if this file's compaction state is
// CompactionStateCompacting. Protected by DB.mu.
func (m *FileMetadata) IsCompacting() bool {
return m.CompactionState == CompactionStateCompacting
}
// StatsValid returns true if the table stats have been populated. If StatValid
// returns true, the Stats field may be read (with or without holding the
// database mutex).
func (m *FileMetadata) StatsValid() bool {
return m.statsValid.Load()
}
// StatsMarkValid marks the TableStats as valid. The caller must hold DB.mu
// while populating TableStats and calling StatsMarkValud. Once stats are
// populated, they must not be mutated.
func (m *FileMetadata) StatsMarkValid() {
m.statsValid.Store(true)
}
// ExtendPointKeyBounds attempts to extend the lower and upper point key bounds
// and overall table bounds with the given smallest and largest keys. The
// smallest and largest bounds may not be extended if the table already has a
// bound that is smaller or larger, respectively. The receiver is returned.
// NB: calling this method should be preferred to manually setting the bounds by
// manipulating the fields directly, to maintain certain invariants.
func (m *FileMetadata) ExtendPointKeyBounds(
cmp Compare, smallest, largest InternalKey,
) *FileMetadata {
// Update the point key bounds.
if !m.HasPointKeys {
m.SmallestPointKey, m.LargestPointKey = smallest, largest
m.HasPointKeys = true
} else {
if base.InternalCompare(cmp, smallest, m.SmallestPointKey) < 0 {
m.SmallestPointKey = smallest
}
if base.InternalCompare(cmp, largest, m.LargestPointKey) > 0 {
m.LargestPointKey = largest
}
}
// Update the overall bounds.
m.extendOverallBounds(cmp, m.SmallestPointKey, m.LargestPointKey, boundTypePointKey)
return m
}
// ExtendRangeKeyBounds attempts to extend the lower and upper range key bounds
// and overall table bounds with the given smallest and largest keys. The
// smallest and largest bounds may not be extended if the table already has a
// bound that is smaller or larger, respectively. The receiver is returned.
// NB: calling this method should be preferred to manually setting the bounds by
// manipulating the fields directly, to maintain certain invariants.
func (m *FileMetadata) ExtendRangeKeyBounds(
cmp Compare, smallest, largest InternalKey,
) *FileMetadata {
// Update the range key bounds.
if !m.HasRangeKeys {
m.SmallestRangeKey, m.LargestRangeKey = smallest, largest
m.HasRangeKeys = true
} else {
if base.InternalCompare(cmp, smallest, m.SmallestRangeKey) < 0 {
m.SmallestRangeKey = smallest
}
if base.InternalCompare(cmp, largest, m.LargestRangeKey) > 0 {
m.LargestRangeKey = largest
}
}
// Update the overall bounds.
m.extendOverallBounds(cmp, m.SmallestRangeKey, m.LargestRangeKey, boundTypeRangeKey)
return m
}
// extendOverallBounds attempts to extend the overall table lower and upper
// bounds. The given bounds may not be used if a lower or upper bound already
// exists that is smaller or larger than the given keys, respectively. The given
// boundType will be used if the bounds are updated.
func (m *FileMetadata) extendOverallBounds(
cmp Compare, smallest, largest InternalKey, bTyp boundType,
) {
if !m.boundsSet {
m.Smallest, m.Largest = smallest, largest
m.boundsSet = true
m.boundTypeSmallest, m.boundTypeLargest = bTyp, bTyp
} else {
if base.InternalCompare(cmp, smallest, m.Smallest) < 0 {
m.Smallest = smallest
m.boundTypeSmallest = bTyp
}
if base.InternalCompare(cmp, largest, m.Largest) > 0 {
m.Largest = largest
m.boundTypeLargest = bTyp
}
}
}
// Overlaps returns true if the file key range overlaps with the given range.
func (m *FileMetadata) Overlaps(cmp Compare, start []byte, end []byte, exclusiveEnd bool) bool {
if c := cmp(m.Largest.UserKey, start); c < 0 || (c == 0 && m.Largest.IsExclusiveSentinel()) {
// f is completely before the specified range; no overlap.
return false
}
if c := cmp(m.Smallest.UserKey, end); c > 0 || (c == 0 && exclusiveEnd) {
// f is completely after the specified range; no overlap.
return false
}
return true
}
// ContainedWithinSpan returns true if the file key range completely overlaps with the
// given range ("end" is assumed to exclusive).
func (m *FileMetadata) ContainedWithinSpan(cmp Compare, start, end []byte) bool {
lowerCmp, upperCmp := cmp(m.Smallest.UserKey, start), cmp(m.Largest.UserKey, end)
return lowerCmp >= 0 && (upperCmp < 0 || (upperCmp == 0 && m.Largest.IsExclusiveSentinel()))
}
// ContainsKeyType returns whether or not the file contains keys of the provided
// type.
func (m *FileMetadata) ContainsKeyType(kt KeyType) bool {
switch kt {
case KeyTypePointAndRange:
return true
case KeyTypePoint:
return m.HasPointKeys
case KeyTypeRange:
return m.HasRangeKeys
default:
panic("unrecognized key type")
}
}
// SmallestBound returns the file's smallest bound of the key type. It returns a
// false second return value if the file does not contain any keys of the key
// type.
func (m *FileMetadata) SmallestBound(kt KeyType) (*InternalKey, bool) {
switch kt {
case KeyTypePointAndRange:
return &m.Smallest, true
case KeyTypePoint:
return &m.SmallestPointKey, m.HasPointKeys
case KeyTypeRange:
return &m.SmallestRangeKey, m.HasRangeKeys
default:
panic("unrecognized key type")
}
}
// LargestBound returns the file's largest bound of the key type. It returns a
// false second return value if the file does not contain any keys of the key
// type.
func (m *FileMetadata) LargestBound(kt KeyType) (*InternalKey, bool) {
switch kt {
case KeyTypePointAndRange:
return &m.Largest, true
case KeyTypePoint:
return &m.LargestPointKey, m.HasPointKeys
case KeyTypeRange:
return &m.LargestRangeKey, m.HasRangeKeys
default:
panic("unrecognized key type")
}
}
const (
maskContainsPointKeys = 1 << 0
maskSmallest = 1 << 1
maskLargest = 1 << 2
)
// boundsMarker returns a marker byte whose bits encode the following
// information (in order from least significant bit):
// - if the table contains point keys
// - if the table's smallest key is a point key
// - if the table's largest key is a point key
func (m *FileMetadata) boundsMarker() (sentinel uint8, err error) {
if m.HasPointKeys {
sentinel |= maskContainsPointKeys
}
switch m.boundTypeSmallest {
case boundTypePointKey:
sentinel |= maskSmallest
case boundTypeRangeKey:
// No op - leave bit unset.
default:
return 0, base.CorruptionErrorf("file %s has neither point nor range key as smallest key", m.FileNum)
}
switch m.boundTypeLargest {
case boundTypePointKey:
sentinel |= maskLargest
case boundTypeRangeKey:
// No op - leave bit unset.
default:
return 0, base.CorruptionErrorf("file %s has neither point nor range key as largest key", m.FileNum)
}
return
}
// String implements fmt.Stringer, printing the file number and the overall
// table bounds.
func (m *FileMetadata) String() string {
return fmt.Sprintf("%s:[%s-%s]", m.FileNum, m.Smallest, m.Largest)
}
// DebugString returns a verbose representation of FileMetadata, typically for
// use in tests and debugging, returning the file number and the point, range
// and overall bounds for the table.
func (m *FileMetadata) DebugString(format base.FormatKey, verbose bool) string {
var b bytes.Buffer
fmt.Fprintf(&b, "%s:[%s-%s]",
m.FileNum, m.Smallest.Pretty(format), m.Largest.Pretty(format))
if !verbose {
return b.String()
}
fmt.Fprintf(&b, " seqnums:[%d-%d]", m.SmallestSeqNum, m.LargestSeqNum)
if m.HasPointKeys {
fmt.Fprintf(&b, " points:[%s-%s]",
m.SmallestPointKey.Pretty(format), m.LargestPointKey.Pretty(format))
}
if m.HasRangeKeys {
fmt.Fprintf(&b, " ranges:[%s-%s]",
m.SmallestRangeKey.Pretty(format), m.LargestRangeKey.Pretty(format))
}
return b.String()
}
// ParseFileMetadataDebug parses a FileMetadata from its DebugString
// representation.
func ParseFileMetadataDebug(s string) (*FileMetadata, error) {
// Split lines of the form:
// 000000:[a#0,SET-z#0,SET] seqnums:[5-5] points:[...] ranges:[...]
fields := strings.FieldsFunc(s, func(c rune) bool {
switch c {
case ':', '[', '-', ']':
return true
default:
return unicode.IsSpace(c) // NB: also trim whitespace padding.
}
})
if len(fields)%3 != 0 {
return nil, errors.Newf("malformed input: %s", s)
}
m := &FileMetadata{}
for len(fields) > 0 {
prefix := fields[0]
if prefix == "seqnums" {
smallestSeqNum, err := strconv.ParseUint(fields[1], 10, 64)
if err != nil {
return m, errors.Newf("malformed input: %s: %s", s, err)
}
largestSeqNum, err := strconv.ParseUint(fields[2], 10, 64)
if err != nil {
return m, errors.Newf("malformed input: %s: %s", s, err)
}
m.SmallestSeqNum, m.LargestSeqNum = smallestSeqNum, largestSeqNum
fields = fields[3:]
continue
}
smallest := base.ParsePrettyInternalKey(fields[1])
largest := base.ParsePrettyInternalKey(fields[2])
switch prefix {
case "points":
m.SmallestPointKey, m.LargestPointKey = smallest, largest
m.HasPointKeys = true
case "ranges":
m.SmallestRangeKey, m.LargestRangeKey = smallest, largest
m.HasRangeKeys = true
default:
fileNum, err := strconv.ParseUint(prefix, 10, 64)
if err != nil {
return m, errors.Newf("malformed input: %s: %s", s, err)
}
m.FileNum = base.FileNum(fileNum)
m.Smallest, m.Largest = smallest, largest
m.boundsSet = true
}
fields = fields[3:]
}
// By default, when the parser sees just the overall bounds, we set the point
// keys. This preserves backwards compatability with existing test cases that
// specify only the overall bounds.
if !m.HasPointKeys && !m.HasRangeKeys {
m.SmallestPointKey, m.LargestPointKey = m.Smallest, m.Largest
m.HasPointKeys = true
}
m.InitPhysicalBacking()
return m, nil
}
// Validate validates the metadata for consistency with itself, returning an
// error if inconsistent.
func (m *FileMetadata) Validate(cmp Compare, formatKey base.FormatKey) error {
// Combined range and point key validation.
if !m.HasPointKeys && !m.HasRangeKeys {
return base.CorruptionErrorf("file %s has neither point nor range keys",
errors.Safe(m.FileNum))
}
if base.InternalCompare(cmp, m.Smallest, m.Largest) > 0 {
return base.CorruptionErrorf("file %s has inconsistent bounds: %s vs %s",
errors.Safe(m.FileNum), m.Smallest.Pretty(formatKey),
m.Largest.Pretty(formatKey))
}
if m.SmallestSeqNum > m.LargestSeqNum {
return base.CorruptionErrorf("file %s has inconsistent seqnum bounds: %d vs %d",
errors.Safe(m.FileNum), m.SmallestSeqNum, m.LargestSeqNum)
}
// Point key validation.
if m.HasPointKeys {
if base.InternalCompare(cmp, m.SmallestPointKey, m.LargestPointKey) > 0 {
return base.CorruptionErrorf("file %s has inconsistent point key bounds: %s vs %s",
errors.Safe(m.FileNum), m.SmallestPointKey.Pretty(formatKey),
m.LargestPointKey.Pretty(formatKey))
}
if base.InternalCompare(cmp, m.SmallestPointKey, m.Smallest) < 0 ||
base.InternalCompare(cmp, m.LargestPointKey, m.Largest) > 0 {
return base.CorruptionErrorf(
"file %s has inconsistent point key bounds relative to overall bounds: "+
"overall = [%s-%s], point keys = [%s-%s]",
errors.Safe(m.FileNum),
m.Smallest.Pretty(formatKey), m.Largest.Pretty(formatKey),
m.SmallestPointKey.Pretty(formatKey), m.LargestPointKey.Pretty(formatKey),
)
}
}
// Range key validation.
if m.HasRangeKeys {
if base.InternalCompare(cmp, m.SmallestRangeKey, m.LargestRangeKey) > 0 {
return base.CorruptionErrorf("file %s has inconsistent range key bounds: %s vs %s",
errors.Safe(m.FileNum), m.SmallestRangeKey.Pretty(formatKey),
m.LargestRangeKey.Pretty(formatKey))
}
if base.InternalCompare(cmp, m.SmallestRangeKey, m.Smallest) < 0 ||
base.InternalCompare(cmp, m.LargestRangeKey, m.Largest) > 0 {
return base.CorruptionErrorf(
"file %s has inconsistent range key bounds relative to overall bounds: "+
"overall = [%s-%s], range keys = [%s-%s]",
errors.Safe(m.FileNum),
m.Smallest.Pretty(formatKey), m.Largest.Pretty(formatKey),
m.SmallestRangeKey.Pretty(formatKey), m.LargestRangeKey.Pretty(formatKey),
)
}
}
// Ensure that FileMetadata.Init was called.
if m.FileBacking == nil {
return base.CorruptionErrorf("file metadata FileBacking not set")
}
return nil
}
// TableInfo returns a subset of the FileMetadata state formatted as a
// TableInfo.
func (m *FileMetadata) TableInfo() TableInfo {
return TableInfo{
FileNum: m.FileNum,
Size: m.Size,
Smallest: m.Smallest,
Largest: m.Largest,
SmallestSeqNum: m.SmallestSeqNum,
LargestSeqNum: m.LargestSeqNum,
}
}
func (m *FileMetadata) cmpSeqNum(b *FileMetadata) int {
// NB: This is the same ordering that RocksDB uses for L0 files.
// Sort first by largest sequence number.
if v := stdcmp.Compare(m.LargestSeqNum, b.LargestSeqNum); v != 0 {
return v
}
// Then by smallest sequence number.
if v := stdcmp.Compare(m.SmallestSeqNum, b.SmallestSeqNum); v != 0 {
return v
}
// Break ties by file number.
return stdcmp.Compare(m.FileNum, b.FileNum)
}
func (m *FileMetadata) lessSeqNum(b *FileMetadata) bool {
return m.cmpSeqNum(b) < 0
}
func (m *FileMetadata) cmpSmallestKey(b *FileMetadata, cmp Compare) int {
return base.InternalCompare(cmp, m.Smallest, b.Smallest)
}
// KeyRange returns the minimum smallest and maximum largest internalKey for
// all the FileMetadata in iters.
func KeyRange(ucmp Compare, iters ...LevelIterator) (smallest, largest InternalKey) {
first := true
for _, iter := range iters {
for meta := iter.First(); meta != nil; meta = iter.Next() {
if first {
first = false
smallest, largest = meta.Smallest, meta.Largest
continue
}
if base.InternalCompare(ucmp, smallest, meta.Smallest) >= 0 {
smallest = meta.Smallest
}
if base.InternalCompare(ucmp, largest, meta.Largest) <= 0 {
largest = meta.Largest
}
}
}
return smallest, largest
}
type bySeqNum []*FileMetadata
func (b bySeqNum) Len() int { return len(b) }
func (b bySeqNum) Less(i, j int) bool {
return b[i].lessSeqNum(b[j])
}
func (b bySeqNum) Swap(i, j int) { b[i], b[j] = b[j], b[i] }
// SortBySeqNum sorts the specified files by increasing sequence number.
func SortBySeqNum(files []*FileMetadata) {
sort.Sort(bySeqNum(files))
}
type bySmallest struct {
files []*FileMetadata
cmp Compare
}
func (b bySmallest) Len() int { return len(b.files) }
func (b bySmallest) Less(i, j int) bool {
return b.files[i].cmpSmallestKey(b.files[j], b.cmp) < 0
}
func (b bySmallest) Swap(i, j int) { b.files[i], b.files[j] = b.files[j], b.files[i] }
// SortBySmallest sorts the specified files by smallest key using the supplied
// comparison function to order user keys.
func SortBySmallest(files []*FileMetadata, cmp Compare) {
sort.Sort(bySmallest{files, cmp})
}
func overlaps(iter LevelIterator, cmp Compare, start, end []byte, exclusiveEnd bool) LevelSlice {
startIter := iter.Clone()
{
startIterFile := startIter.SeekGE(cmp, start)
// SeekGE compares user keys. The user key `start` may be equal to the
// f.Largest because f.Largest is a range deletion sentinel, indicating
// that the user key `start` is NOT contained within the file f. If
// that's the case, we can narrow the overlapping bounds to exclude the
// file with the sentinel.
if startIterFile != nil && startIterFile.Largest.IsExclusiveSentinel() &&
cmp(startIterFile.Largest.UserKey, start) == 0 {
startIterFile = startIter.Next()
}
_ = startIterFile // Ignore unused assignment.
}
endIter := iter.Clone()
{
endIterFile := endIter.SeekGE(cmp, end)
if !exclusiveEnd {
// endIter is now pointing at the *first* file with a largest key >= end.
// If there are multiple files including the user key `end`, we want all
// of them, so move forward.
for endIterFile != nil && cmp(endIterFile.Largest.UserKey, end) == 0 {
endIterFile = endIter.Next()
}
}
// LevelSlice uses inclusive bounds, so if we seeked to the end sentinel
// or nexted too far because Largest.UserKey equaled `end`, go back.
//
// Consider !exclusiveEnd and end = 'f', with the following file bounds:
//
// [b,d] [e, f] [f, f] [g, h]
//
// the above for loop will Next until it arrives at [g, h]. We need to
// observe that g > f, and Prev to the file with bounds [f, f].
if endIterFile == nil {
endIterFile = endIter.Prev()
} else if c := cmp(endIterFile.Smallest.UserKey, end); c > 0 || c == 0 && exclusiveEnd {
endIterFile = endIter.Prev()
}
_ = endIterFile // Ignore unused assignment.
}
return newBoundedLevelSlice(startIter.Clone().iter, &startIter.iter, &endIter.iter)
}
// NumLevels is the number of levels a Version contains.
const NumLevels = 7
// NewVersion constructs a new Version with the provided files. It requires
// the provided files are already well-ordered. It's intended for testing.
func NewVersion(
cmp Compare, formatKey base.FormatKey, flushSplitBytes int64, files [NumLevels][]*FileMetadata,
) *Version {
var v Version
for l := range files {
// NB: We specifically insert `files` into the B-Tree in the order
// they appear within `files`. Some tests depend on this behavior in
// order to test consistency checking, etc. Once we've constructed the
// initial B-Tree, we swap out the btreeCmp for the correct one.
// TODO(jackson): Adjust or remove the tests and remove this.
v.Levels[l].tree, _ = makeBTree(btreeCmpSpecificOrder(files[l]), files[l])
v.Levels[l].level = l
if l == 0 {
v.Levels[l].tree.cmp = btreeCmpSeqNum
} else {
v.Levels[l].tree.cmp = btreeCmpSmallestKey(cmp)
}
for _, f := range files[l] {
v.Levels[l].totalSize += f.Size
}
}
if err := v.InitL0Sublevels(cmp, formatKey, flushSplitBytes); err != nil {
panic(err)
}
return &v
}
// Version is a collection of file metadata for on-disk tables at various
// levels. In-memory DBs are written to level-0 tables, and compactions
// migrate data from level N to level N+1. The tables map internal keys (which
// are a user key, a delete or set bit, and a sequence number) to user values.
//
// The tables at level 0 are sorted by largest sequence number. Due to file
// ingestion, there may be overlap in the ranges of sequence numbers contain in
// level 0 sstables. In particular, it is valid for one level 0 sstable to have
// the seqnum range [1,100] while an adjacent sstable has the seqnum range
// [50,50]. This occurs when the [50,50] table was ingested and given a global
// seqnum. The ingestion code will have ensured that the [50,50] sstable will
// not have any keys that overlap with the [1,100] in the seqnum range
// [1,49]. The range of internal keys [fileMetadata.smallest,
// fileMetadata.largest] in each level 0 table may overlap.
//
// The tables at any non-0 level are sorted by their internal key range and any
// two tables at the same non-0 level do not overlap.
//
// The internal key ranges of two tables at different levels X and Y may
// overlap, for any X != Y.
//
// Finally, for every internal key in a table at level X, there is no internal
// key in a higher level table that has both the same user key and a higher
// sequence number.
type Version struct {
refs atomic.Int32
// The level 0 sstables are organized in a series of sublevels. Similar to
// the seqnum invariant in normal levels, there is no internal key in a
// higher level table that has both the same user key and a higher sequence
// number. Within a sublevel, tables are sorted by their internal key range
// and any two tables at the same sublevel do not overlap. Unlike the normal
// levels, sublevel n contains older tables (lower sequence numbers) than
// sublevel n+1.
//
// The L0Sublevels struct is mostly used for compaction picking. As most
// internal data structures in it are only necessary for compaction picking
// and not for iterator creation, the reference to L0Sublevels is nil'd
// after this version becomes the non-newest version, to reduce memory
// usage.
//
// L0Sublevels.Levels contains L0 files ordered by sublevels. All the files
// in Levels[0] are in L0Sublevels.Levels. L0SublevelFiles is also set to
// a reference to that slice, as that slice is necessary for iterator
// creation and needs to outlast L0Sublevels.
L0Sublevels *L0Sublevels
L0SublevelFiles []LevelSlice
Levels [NumLevels]LevelMetadata
// RangeKeyLevels holds a subset of the same files as Levels that contain range
// keys (i.e. fileMeta.HasRangeKeys == true). The memory amplification of this
// duplication should be minimal, as range keys are expected to be rare.
RangeKeyLevels [NumLevels]LevelMetadata
// The callback to invoke when the last reference to a version is
// removed. Will be called with list.mu held.
Deleted func(obsolete []*FileBacking)
// Stats holds aggregated stats about the version maintained from
// version to version.
Stats struct {
// MarkedForCompaction records the count of files marked for
// compaction within the version.
MarkedForCompaction int
}
// The list the version is linked into.
list *VersionList
// The next/prev link for the versionList doubly-linked list of versions.
prev, next *Version
}
// String implements fmt.Stringer, printing the FileMetadata for each level in
// the Version.
func (v *Version) String() string {
return v.string(base.DefaultFormatter, false)
}
// DebugString returns an alternative format to String() which includes sequence
// number and kind information for the sstable boundaries.
func (v *Version) DebugString(format base.FormatKey) string {
return v.string(format, true)
}
func describeSublevels(format base.FormatKey, verbose bool, sublevels []LevelSlice) string {
var buf bytes.Buffer
for sublevel := len(sublevels) - 1; sublevel >= 0; sublevel-- {
fmt.Fprintf(&buf, "0.%d:\n", sublevel)
sublevels[sublevel].Each(func(f *FileMetadata) {
fmt.Fprintf(&buf, " %s\n", f.DebugString(format, verbose))
})
}
return buf.String()
}
func (v *Version) string(format base.FormatKey, verbose bool) string {
var buf bytes.Buffer
if len(v.L0SublevelFiles) > 0 {
fmt.Fprintf(&buf, "%s", describeSublevels(format, verbose, v.L0SublevelFiles))
}
for level := 1; level < NumLevels; level++ {
if v.Levels[level].Empty() {
continue
}
fmt.Fprintf(&buf, "%d:\n", level)
iter := v.Levels[level].Iter()
for f := iter.First(); f != nil; f = iter.Next() {
fmt.Fprintf(&buf, " %s\n", f.DebugString(format, verbose))
}
}
return buf.String()
}
// ParseVersionDebug parses a Version from its DebugString output.
func ParseVersionDebug(
cmp Compare, formatKey base.FormatKey, flushSplitBytes int64, s string,
) (*Version, error) {
var level int
var files [NumLevels][]*FileMetadata
for _, l := range strings.Split(s, "\n") {
l = strings.TrimSpace(l)
switch l[:2] {
case "0.", "0:", "1:", "2:", "3:", "4:", "5:", "6:":
var err error
level, err = strconv.Atoi(l[:1])
if err != nil {
return nil, err
}
default:
m, err := ParseFileMetadataDebug(l)
if err != nil {
return nil, err
}
// If we only parsed overall bounds, default to setting the point bounds.
if !m.HasPointKeys && !m.HasRangeKeys {
m.SmallestPointKey, m.LargestPointKey = m.Smallest, m.Largest
m.HasPointKeys = true
}
files[level] = append(files[level], m)
}
}
// Reverse the order of L0 files. This ensures we construct the same
// sublevels. (They're printed from higher sublevel to lower, which means in
// a partial order that represents newest to oldest).
for i := 0; i < len(files[0])/2; i++ {
files[0][i], files[0][len(files[0])-i-1] = files[0][len(files[0])-i-1], files[0][i]
}
return NewVersion(cmp, formatKey, flushSplitBytes, files), nil
}
// Refs returns the number of references to the version.
func (v *Version) Refs() int32 {
return v.refs.Load()
}
// Ref increments the version refcount.
func (v *Version) Ref() {
v.refs.Add(1)
}
// Unref decrements the version refcount. If the last reference to the version
// was removed, the version is removed from the list of versions and the
// Deleted callback is invoked. Requires that the VersionList mutex is NOT
// locked.
func (v *Version) Unref() {
if v.refs.Add(-1) == 0 {
l := v.list
l.mu.Lock()
l.Remove(v)
v.Deleted(v.unrefFiles())
l.mu.Unlock()
}
}
// UnrefLocked decrements the version refcount. If the last reference to the
// version was removed, the version is removed from the list of versions and
// the Deleted callback is invoked. Requires that the VersionList mutex is
// already locked.
func (v *Version) UnrefLocked() {
if v.refs.Add(-1) == 0 {
v.list.Remove(v)
v.Deleted(v.unrefFiles())
}
}
func (v *Version) unrefFiles() []*FileBacking {
var obsolete []*FileBacking
for _, lm := range v.Levels {
obsolete = append(obsolete, lm.release()...)
}
for _, lm := range v.RangeKeyLevels {
obsolete = append(obsolete, lm.release()...)
}
return obsolete
}
// Next returns the next version in the list of versions.
func (v *Version) Next() *Version {
return v.next
}
// InitL0Sublevels initializes the L0Sublevels
func (v *Version) InitL0Sublevels(
cmp Compare, formatKey base.FormatKey, flushSplitBytes int64,
) error {
var err error
v.L0Sublevels, err = NewL0Sublevels(&v.Levels[0], cmp, formatKey, flushSplitBytes)
if err == nil && v.L0Sublevels != nil {
v.L0SublevelFiles = v.L0Sublevels.Levels
}
return err
}
// Contains returns a boolean indicating whether the provided file exists in
// the version at the given level. If level is non-zero then Contains binary
// searches among the files. If level is zero, Contains scans the entire
// level.
func (v *Version) Contains(level int, cmp Compare, m *FileMetadata) bool {
iter := v.Levels[level].Iter()
if level > 0 {
overlaps := v.Overlaps(level, cmp, m.Smallest.UserKey, m.Largest.UserKey,
m.Largest.IsExclusiveSentinel())
iter = overlaps.Iter()
}
for f := iter.First(); f != nil; f = iter.Next() {
if f == m {
return true
}
}
return false
}
// Overlaps returns all elements of v.files[level] whose user key range
// intersects the given range. If level is non-zero then the user key ranges of
// v.files[level] are assumed to not overlap (although they may touch). If level
// is zero then that assumption cannot be made, and the [start, end] range is
// expanded to the union of those matching ranges so far and the computation is
// repeated until [start, end] stabilizes.
// The returned files are a subsequence of the input files, i.e., the ordering
// is not changed.
func (v *Version) Overlaps(
level int, cmp Compare, start, end []byte, exclusiveEnd bool,
) LevelSlice {
if level == 0 {
// Indices that have been selected as overlapping.
l0 := v.Levels[level]
l0Iter := l0.Iter()
selectedIndices := make([]bool, l0.Len())
numSelected := 0
var slice LevelSlice
for {
restart := false
for i, meta := 0, l0Iter.First(); meta != nil; i, meta = i+1, l0Iter.Next() {
selected := selectedIndices[i]
if selected {
continue
}
if !meta.Overlaps(cmp, start, end, exclusiveEnd) {
// meta is completely outside the specified range; skip it.
continue
}
// Overlaps.
selectedIndices[i] = true
numSelected++
smallest := meta.Smallest.UserKey
largest := meta.Largest.UserKey
// Since level == 0, check if the newly added fileMetadata has
// expanded the range. We expand the range immediately for files
// we have remaining to check in this loop. All already checked
// and unselected files will need to be rechecked via the
// restart below.
if cmp(smallest, start) < 0 {
start = smallest
restart = true
}
if v := cmp(largest, end); v > 0 {
end = largest
exclusiveEnd = meta.Largest.IsExclusiveSentinel()
restart = true
} else if v == 0 && exclusiveEnd && !meta.Largest.IsExclusiveSentinel() {
// Only update the exclusivity of our existing `end`
// bound.
exclusiveEnd = false
restart = true
}
}
if !restart {
// Construct a B-Tree containing only the matching items.
var tr btree
tr.cmp = v.Levels[level].tree.cmp
for i, meta := 0, l0Iter.First(); meta != nil; i, meta = i+1, l0Iter.Next() {
if selectedIndices[i] {
err := tr.Insert(meta)
if err != nil {
panic(err)
}
}
}
slice = newLevelSlice(tr.Iter())
// TODO(jackson): Avoid the oddity of constructing and
// immediately releasing a B-Tree. Make LevelSlice an
// interface?
tr.Release()
break
}
// Continue looping to retry the files that were not selected.
}
return slice
}
return overlaps(v.Levels[level].Iter(), cmp, start, end, exclusiveEnd)
}
// CheckOrdering checks that the files are consistent with respect to
// increasing file numbers (for level 0 files) and increasing and non-
// overlapping internal key ranges (for level non-0 files).
func (v *Version) CheckOrdering(
cmp Compare, format base.FormatKey, order OrderingInvariants,
) error {
for sublevel := len(v.L0SublevelFiles) - 1; sublevel >= 0; sublevel-- {
sublevelIter := v.L0SublevelFiles[sublevel].Iter()
// Sublevels have NEVER allowed split user keys, so we can pass
// ProhibitSplitUserKeys.
if err := CheckOrdering(cmp, format, L0Sublevel(sublevel), sublevelIter, ProhibitSplitUserKeys); err != nil {
return base.CorruptionErrorf("%s\n%s", err, v.DebugString(format))
}
}
for level, lm := range v.Levels {
if err := CheckOrdering(cmp, format, Level(level), lm.Iter(), order); err != nil {
return base.CorruptionErrorf("%s\n%s", err, v.DebugString(format))
}
}
return nil
}
// VersionList holds a list of versions. The versions are ordered from oldest
// to newest.
type VersionList struct {
mu *sync.Mutex
root Version
}
// Init initializes the version list.
func (l *VersionList) Init(mu *sync.Mutex) {
l.mu = mu
l.root.next = &l.root
l.root.prev = &l.root
}
// Empty returns true if the list is empty, and false otherwise.
func (l *VersionList) Empty() bool {
return l.root.next == &l.root
}
// Front returns the oldest version in the list. Note that this version is only
// valid if Empty() returns true.
func (l *VersionList) Front() *Version {
return l.root.next
}
// Back returns the newest version in the list. Note that this version is only
// valid if Empty() returns true.
func (l *VersionList) Back() *Version {
return l.root.prev
}
// PushBack adds a new version to the back of the list. This new version
// becomes the "newest" version in the list.
func (l *VersionList) PushBack(v *Version) {
if v.list != nil || v.prev != nil || v.next != nil {
panic("pebble: version list is inconsistent")
}
v.prev = l.root.prev
v.prev.next = v
v.next = &l.root
v.next.prev = v
v.list = l
// Let L0Sublevels on the second newest version get GC'd, as it is no longer
// necessary. See the comment in Version.
v.prev.L0Sublevels = nil
}
// Remove removes the specified version from the list.
func (l *VersionList) Remove(v *Version) {
if v == &l.root {
panic("pebble: cannot remove version list root node")
}
if v.list != l {
panic("pebble: version list is inconsistent")
}
v.prev.next = v.next
v.next.prev = v.prev
v.next = nil // avoid memory leaks
v.prev = nil // avoid memory leaks
v.list = nil // avoid memory leaks
}
// OrderingInvariants dictates the file ordering invariants active.
type OrderingInvariants int8
const (
// ProhibitSplitUserKeys indicates that adjacent files within a level cannot
// contain the same user key.
ProhibitSplitUserKeys OrderingInvariants = iota
// AllowSplitUserKeys indicates that adjacent files within a level may
// contain the same user key. This is only allowed by historical format
// major versions.
//
// TODO(jackson): Remove.
AllowSplitUserKeys
)
// CheckOrdering checks that the files are consistent with respect to
// seqnums (for level 0 files -- see detailed comment below) and increasing and non-
// overlapping internal key ranges (for non-level 0 files).
//
// The ordering field may be passed AllowSplitUserKeys to allow adjacent files that are both
// inclusive of the same user key. Pebble no longer creates version edits
// installing such files, and Pebble databases with sufficiently high format
// major version should no longer have any such files within their LSM.
// TODO(jackson): Remove AllowSplitUserKeys when we remove support for the
// earlier format major versions.
func CheckOrdering(
cmp Compare, format base.FormatKey, level Level, files LevelIterator, ordering OrderingInvariants,
) error {
// The invariants to check for L0 sublevels are the same as the ones to
// check for all other levels. However, if L0 is not organized into
// sublevels, or if all L0 files are being passed in, we do the legacy L0
// checks, defined in the detailed comment below.
if level == Level(0) {
// We have 2 kinds of files:
// - Files with exactly one sequence number: these could be either ingested files
// or flushed files. We cannot tell the difference between them based on FileMetadata,
// so our consistency checking here uses the weaker checks assuming it is a narrow
// flushed file. We cannot error on ingested files having sequence numbers coincident
// with flushed files as the seemingly ingested file could just be a flushed file
// with just one key in it which is a truncated range tombstone sharing sequence numbers
// with other files in the same flush.
// - Files with multiple sequence numbers: these are necessarily flushed files.
//
// Three cases of overlapping sequence numbers:
// Case 1:
// An ingested file contained in the sequence numbers of the flushed file -- it must be
// fully contained (not coincident with either end of the flushed file) since the memtable
// must have been at [a, b-1] (where b > a) when the ingested file was assigned sequence
// num b, and the memtable got a subsequent update that was given sequence num b+1, before
// being flushed.
//
// So a sequence [1000, 1000] [1002, 1002] [1000, 2000] is invalid since the first and
// third file are inconsistent with each other. So comparing adjacent files is insufficient
// for consistency checking.
//
// Visually we have something like
// x------y x-----------yx-------------y (flushed files where x, y are the endpoints)
// y y y y (y's represent ingested files)
// And these are ordered in increasing order of y. Note that y's must be unique.
//
// Case 2:
// A flushed file that did not overlap in keys with any file in any level, but does overlap
// in the file key intervals. This file is placed in L0 since it overlaps in the file
// key intervals but since it has no overlapping data, it is assigned a sequence number
// of 0 in RocksDB. We handle this case for compatibility with RocksDB.
//
// Case 3:
// A sequence of flushed files that overlap in sequence numbers with one another,
// but do not overlap in keys inside the sstables. These files correspond to
// partitioned flushes or the results of intra-L0 compactions of partitioned
// flushes.
//
// Since these types of SSTables violate most other sequence number
// overlap invariants, and handling this case is important for compatibility
// with future versions of pebble, this method relaxes most L0 invariant
// checks.
var prev *FileMetadata
for f := files.First(); f != nil; f, prev = files.Next(), f {
if prev == nil {
continue
}
// Validate that the sorting is sane.
if prev.LargestSeqNum == 0 && f.LargestSeqNum == prev.LargestSeqNum {
// Multiple files satisfying case 2 mentioned above.
} else if !prev.lessSeqNum(f) {
return base.CorruptionErrorf("L0 files %s and %s are not properly ordered: <#%d-#%d> vs <#%d-#%d>",
errors.Safe(prev.FileNum), errors.Safe(f.FileNum),
errors.Safe(prev.SmallestSeqNum), errors.Safe(prev.LargestSeqNum),
errors.Safe(f.SmallestSeqNum), errors.Safe(f.LargestSeqNum))
}
}
} else {
var prev *FileMetadata
for f := files.First(); f != nil; f, prev = files.Next(), f {
if err := f.Validate(cmp, format); err != nil {
return errors.Wrapf(err, "%s ", level)
}
if prev != nil {
if prev.cmpSmallestKey(f, cmp) >= 0 {
return base.CorruptionErrorf("%s files %s and %s are not properly ordered: [%s-%s] vs [%s-%s]",
errors.Safe(level), errors.Safe(prev.FileNum), errors.Safe(f.FileNum),
prev.Smallest.Pretty(format), prev.Largest.Pretty(format),
f.Smallest.Pretty(format), f.Largest.Pretty(format))
}
// What's considered "overlapping" is dependent on the format
// major version. If ordering=ProhibitSplitUserKeys, then both
// files cannot contain keys with the same user keys. If the
// bounds have the same user key, the previous file's boundary
// must have a Trailer indicating that it's exclusive.
switch ordering {
case AllowSplitUserKeys:
if base.InternalCompare(cmp, prev.Largest, f.Smallest) >= 0 {
return base.CorruptionErrorf("%s files %s and %s have overlapping ranges: [%s-%s] vs [%s-%s]",
errors.Safe(level), errors.Safe(prev.FileNum), errors.Safe(f.FileNum),
prev.Smallest.Pretty(format), prev.Largest.Pretty(format),
f.Smallest.Pretty(format), f.Largest.Pretty(format))
}
case ProhibitSplitUserKeys:
if v := cmp(prev.Largest.UserKey, f.Smallest.UserKey); v > 0 || (v == 0 && !prev.Largest.IsExclusiveSentinel()) {
return base.CorruptionErrorf("%s files %s and %s have overlapping ranges: [%s-%s] vs [%s-%s]",
errors.Safe(level), errors.Safe(prev.FileNum), errors.Safe(f.FileNum),
prev.Smallest.Pretty(format), prev.Largest.Pretty(format),
f.Smallest.Pretty(format), f.Largest.Pretty(format))
}
default:
panic("unreachable")
}
}
}
}
return nil
}