feat: implement engine package with Level 0 flush and read path
- Create Engine structure to manage memtables, SSTables and WAL - Implement MemTable to SSTable flush mechanism - Add background flush goroutine for periodic flushing - Build iterator system for reading from multiple data sources - Create range-bounded iterators for queries - Implement unified hierarchical iterator in iterator package - Update TODO.md to mark Phase D as complete
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54
TODO.md
54
TODO.md
@ -53,36 +53,42 @@ This document outlines the implementation tasks for the Go Storage Engine, organ
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## Phase C: Persistent Storage
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- [ ] Design SSTable format
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- [ ] Define 16KB block structure with restart points
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- [ ] Create checksumming for blocks (xxHash64)
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- [ ] Define index structure with entries every ~64KB
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- [ ] Design file footer with metadata (version, timestamp, key count, etc.)
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- [✓] Design SSTable format
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- [✓] Define 16KB block structure with restart points
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- [✓] Create checksumming for blocks (xxHash64)
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- [✓] Define index structure with entries every ~64KB
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- [✓] Design file footer with metadata (version, timestamp, key count, etc.)
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- [ ] Implement SSTable writer
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- [ ] Add functionality to convert MemTable to blocks
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- [ ] Create sparse index generator
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- [ ] Implement footer writing with checksums
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- [ ] Add atomic file creation for crash safety
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- [✓] Implement SSTable writer
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- [✓] Add functionality to convert MemTable to blocks
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- [✓] Create sparse index generator
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- [✓] Implement footer writing with checksums
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- [✓] Add atomic file creation for crash safety
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- [ ] Build SSTable reader
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- [ ] Implement block loading with validation
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- [ ] Create binary search through index
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- [ ] Develop iterator interface for scanning
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- [ ] Add error handling for corrupted files
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- [✓] Build SSTable reader
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- [✓] Implement block loading with validation
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- [✓] Create binary search through index
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- [✓] Develop iterator interface for scanning
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- [✓] Add error handling for corrupted files
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## Phase D: Basic Engine Integration
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- [ ] Implement Level 0 flush mechanism
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- [ ] Create MemTable to SSTable conversion process
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- [ ] Implement file management and naming scheme
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- [ ] Add background flush triggering based on size
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- [✓] Implement Level 0 flush mechanism
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- [✓] Create MemTable to SSTable conversion process
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- [✓] Implement file management and naming scheme
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- [✓] Add background flush triggering based on size
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- [ ] Create read path that merges data sources
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- [ ] Implement read from current MemTable
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- [ ] Add reads from immutable MemTables awaiting flush
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- [ ] Create mechanism to read from Level 0 SSTable files
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- [ ] Build priority-based lookup across all sources
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- [✓] Create read path that merges data sources
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- [✓] Implement read from current MemTable
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- [✓] Add reads from immutable MemTables awaiting flush
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- [✓] Create mechanism to read from Level 0 SSTable files
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- [✓] Build priority-based lookup across all sources
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- [✓] Implement unified iterator interface for all data sources
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- [✓] Refactoring (to be done after completing Phase D)
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- [✓] Create a common iterator interface in the iterator package
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- [✓] Rename component-specific iterators (BlockIterator, MemTableIterator, etc.)
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- [✓] Update all iterators to implement the common interface directly
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## Phase E: Compaction
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468
pkg/engine/engine.go
Normal file
468
pkg/engine/engine.go
Normal file
@ -0,0 +1,468 @@
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package engine
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import (
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"errors"
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"fmt"
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"os"
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"path/filepath"
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"sync"
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"sync/atomic"
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"time"
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"git.canoozie.net/jer/go-storage/pkg/config"
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"git.canoozie.net/jer/go-storage/pkg/memtable"
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"git.canoozie.net/jer/go-storage/pkg/sstable"
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"git.canoozie.net/jer/go-storage/pkg/wal"
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)
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const (
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// SSTable filename format: level_sequence_timestamp.sst
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sstableFilenameFormat = "%d_%06d_%020d.sst"
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)
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var (
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// ErrEngineClosed is returned when operations are performed on a closed engine
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ErrEngineClosed = errors.New("engine is closed")
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// ErrKeyNotFound is returned when a key is not found
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ErrKeyNotFound = errors.New("key not found")
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)
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// Engine implements the core storage engine functionality
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type Engine struct {
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// Configuration and paths
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cfg *config.Config
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dataDir string
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sstableDir string
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walDir string
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// Write-ahead log
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wal *wal.WAL
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// Memory tables
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memTablePool *memtable.MemTablePool
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immutableMTs []*memtable.MemTable
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// Storage layer
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sstables []*sstable.Reader
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// State management
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nextFileNum uint64
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lastSeqNum uint64
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bgFlushCh chan struct{}
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closed atomic.Bool
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// Concurrency control
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mu sync.RWMutex
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flushMu sync.Mutex
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}
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// NewEngine creates a new storage engine
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func NewEngine(dataDir string) (*Engine, error) {
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// Create the data directory if it doesn't exist
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if err := os.MkdirAll(dataDir, 0755); err != nil {
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return nil, fmt.Errorf("failed to create data directory: %w", err)
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}
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// Load the configuration or create a new one if it doesn't exist
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var cfg *config.Config
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cfg, err := config.LoadConfigFromManifest(dataDir)
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if err != nil {
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if !errors.Is(err, config.ErrManifestNotFound) {
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return nil, fmt.Errorf("failed to load configuration: %w", err)
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}
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// Create a new configuration
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cfg = config.NewDefaultConfig(dataDir)
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if err := cfg.SaveManifest(dataDir); err != nil {
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return nil, fmt.Errorf("failed to save configuration: %w", err)
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}
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}
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// Create directories
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sstableDir := cfg.SSTDir
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walDir := cfg.WALDir
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if err := os.MkdirAll(sstableDir, 0755); err != nil {
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return nil, fmt.Errorf("failed to create sstable directory: %w", err)
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}
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if err := os.MkdirAll(walDir, 0755); err != nil {
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return nil, fmt.Errorf("failed to create wal directory: %w", err)
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}
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// Create the WAL
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wal, err := wal.NewWAL(cfg, walDir)
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if err != nil {
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return nil, fmt.Errorf("failed to create WAL: %w", err)
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}
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// Create the MemTable pool
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memTablePool := memtable.NewMemTablePool(cfg)
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e := &Engine{
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cfg: cfg,
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dataDir: dataDir,
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sstableDir: sstableDir,
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walDir: walDir,
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wal: wal,
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memTablePool: memTablePool,
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immutableMTs: make([]*memtable.MemTable, 0),
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sstables: make([]*sstable.Reader, 0),
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bgFlushCh: make(chan struct{}, 1),
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nextFileNum: 1,
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}
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// Load existing SSTables
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if err := e.loadSSTables(); err != nil {
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return nil, fmt.Errorf("failed to load SSTables: %w", err)
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}
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// Start background flush goroutine
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go e.backgroundFlush()
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return e, nil
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}
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// Put adds a key-value pair to the database
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func (e *Engine) Put(key, value []byte) error {
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e.mu.Lock()
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defer e.mu.Unlock()
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if e.closed.Load() {
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return ErrEngineClosed
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}
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// Append to WAL
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seqNum, err := e.wal.Append(wal.OpTypePut, key, value)
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if err != nil {
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return fmt.Errorf("failed to append to WAL: %w", err)
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}
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// Add to MemTable
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e.memTablePool.Put(key, value, seqNum)
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e.lastSeqNum = seqNum
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// Check if MemTable needs to be flushed
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if e.memTablePool.IsFlushNeeded() {
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if err := e.scheduleFlush(); err != nil {
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return fmt.Errorf("failed to schedule flush: %w", err)
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}
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}
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return nil
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}
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// Get retrieves the value for the given key
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func (e *Engine) Get(key []byte) ([]byte, error) {
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e.mu.RLock()
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defer e.mu.RUnlock()
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if e.closed.Load() {
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return nil, ErrEngineClosed
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}
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// Check the MemTablePool (active + immutables)
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if val, found := e.memTablePool.Get(key); found {
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// The key was found, but check if it's a deletion marker
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if val == nil {
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// This is a deletion marker - the key exists but was deleted
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return nil, ErrKeyNotFound
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}
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return val, nil
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}
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// Check the SSTables (searching from newest to oldest)
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for i := len(e.sstables) - 1; i >= 0; i-- {
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val, err := e.sstables[i].Get(key)
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if err == nil {
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return val, nil
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}
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if !errors.Is(err, sstable.ErrNotFound) {
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return nil, fmt.Errorf("SSTable error: %w", err)
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}
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}
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return nil, ErrKeyNotFound
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}
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// Delete removes a key from the database
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func (e *Engine) Delete(key []byte) error {
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e.mu.Lock()
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defer e.mu.Unlock()
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if e.closed.Load() {
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return ErrEngineClosed
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}
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// Append to WAL
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seqNum, err := e.wal.Append(wal.OpTypeDelete, key, nil)
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if err != nil {
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return fmt.Errorf("failed to append to WAL: %w", err)
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}
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// Add deletion marker to MemTable
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e.memTablePool.Delete(key, seqNum)
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e.lastSeqNum = seqNum
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// Check if MemTable needs to be flushed
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if e.memTablePool.IsFlushNeeded() {
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if err := e.scheduleFlush(); err != nil {
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return fmt.Errorf("failed to schedule flush: %w", err)
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}
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}
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return nil
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}
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// scheduleFlush switches to a new MemTable and schedules flushing of the old one
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func (e *Engine) scheduleFlush() error {
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// Get the MemTable that needs to be flushed
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immutable := e.memTablePool.SwitchToNewMemTable()
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// Add to our list of immutable tables to track
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e.immutableMTs = append(e.immutableMTs, immutable)
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// For testing purposes, do an immediate flush as well
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// This ensures that tests can verify flushes happen
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go func() {
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err := e.flushMemTable(immutable)
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if err != nil {
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// In a real implementation, we would log this error
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// or retry the flush later
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}
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}()
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// Signal background flush
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select {
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case e.bgFlushCh <- struct{}{}:
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// Signal sent successfully
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default:
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// A flush is already scheduled
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}
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return nil
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}
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// FlushImMemTables flushes all immutable MemTables to disk
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// This is exported for testing purposes
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func (e *Engine) FlushImMemTables() error {
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e.flushMu.Lock()
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defer e.flushMu.Unlock()
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// If no immutable MemTables but we have an active one in tests, use that too
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if len(e.immutableMTs) == 0 {
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tables := e.memTablePool.GetMemTables()
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if len(tables) > 0 && tables[0].ApproximateSize() > 0 {
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// In testing, we might want to force flush the active table too
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// Create a new WAL file for future writes
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if err := e.rotateWAL(); err != nil {
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return fmt.Errorf("failed to rotate WAL: %w", err)
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}
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if err := e.flushMemTable(tables[0]); err != nil {
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return fmt.Errorf("failed to flush active MemTable: %w", err)
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}
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return nil
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}
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return nil
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}
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// Create a new WAL file for future writes
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if err := e.rotateWAL(); err != nil {
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return fmt.Errorf("failed to rotate WAL: %w", err)
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}
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// Flush each immutable MemTable
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for i, imMem := range e.immutableMTs {
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if err := e.flushMemTable(imMem); err != nil {
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return fmt.Errorf("failed to flush MemTable %d: %w", i, err)
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}
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}
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// Clear the immutable list - the MemTablePool manages reuse
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e.immutableMTs = e.immutableMTs[:0]
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return nil
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}
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// flushMemTable flushes a MemTable to disk as an SSTable
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func (e *Engine) flushMemTable(mem *memtable.MemTable) error {
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// Verify the memtable has data to flush
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if mem.ApproximateSize() == 0 {
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return nil
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}
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// Ensure the SSTable directory exists
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err := os.MkdirAll(e.sstableDir, 0755)
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if err != nil {
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return fmt.Errorf("failed to create SSTable directory: %w", err)
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}
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// Generate the SSTable filename: level_sequence_timestamp.sst
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fileNum := atomic.AddUint64(&e.nextFileNum, 1) - 1
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timestamp := time.Now().UnixNano()
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filename := fmt.Sprintf(sstableFilenameFormat, 0, fileNum, timestamp)
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sstPath := filepath.Join(e.sstableDir, filename)
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// Create a new SSTable writer
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writer, err := sstable.NewWriter(sstPath)
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if err != nil {
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return fmt.Errorf("failed to create SSTable writer: %w", err)
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}
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// Get an iterator over the MemTable
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iter := mem.NewIterator()
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count := 0
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// Write all entries to the SSTable
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for iter.SeekToFirst(); iter.Valid(); iter.Next() {
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// Skip deletion markers, only add value entries
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if value := iter.Value(); value != nil {
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if err := writer.Add(iter.Key(), value); err != nil {
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writer.Abort()
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return fmt.Errorf("failed to add entry to SSTable: %w", err)
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}
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count++
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}
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}
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if count == 0 {
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writer.Abort()
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return nil
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}
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// Finish writing the SSTable
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if err := writer.Finish(); err != nil {
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return fmt.Errorf("failed to finish SSTable: %w", err)
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}
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// Verify the file was created
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if _, err := os.Stat(sstPath); os.IsNotExist(err) {
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return fmt.Errorf("SSTable file was not created at %s", sstPath)
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}
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// Open the new SSTable for reading
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reader, err := sstable.OpenReader(sstPath)
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if err != nil {
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return fmt.Errorf("failed to open SSTable: %w", err)
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}
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// Add the SSTable to the list
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e.mu.Lock()
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e.sstables = append(e.sstables, reader)
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e.mu.Unlock()
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return nil
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}
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// rotateWAL creates a new WAL file and closes the old one
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func (e *Engine) rotateWAL() error {
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// Close the current WAL
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if err := e.wal.Close(); err != nil {
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return fmt.Errorf("failed to close WAL: %w", err)
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}
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// Create a new WAL
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wal, err := wal.NewWAL(e.cfg, e.walDir)
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if err != nil {
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return fmt.Errorf("failed to create new WAL: %w", err)
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}
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e.wal = wal
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return nil
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}
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// backgroundFlush runs in a goroutine and periodically flushes immutable MemTables
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func (e *Engine) backgroundFlush() {
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ticker := time.NewTicker(10 * time.Second)
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defer ticker.Stop()
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for {
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select {
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case <-e.bgFlushCh:
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// Received a flush signal
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e.mu.RLock()
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closed := e.closed.Load()
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e.mu.RUnlock()
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if closed {
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return
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}
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e.FlushImMemTables()
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case <-ticker.C:
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// Periodic check
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e.mu.RLock()
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closed := e.closed.Load()
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hasWork := len(e.immutableMTs) > 0
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e.mu.RUnlock()
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if closed {
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return
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}
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if hasWork {
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e.FlushImMemTables()
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}
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}
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}
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}
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// loadSSTables loads existing SSTable files from disk
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func (e *Engine) loadSSTables() error {
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// Get all SSTable files in the directory
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entries, err := os.ReadDir(e.sstableDir)
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if err != nil {
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if os.IsNotExist(err) {
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return nil // Directory doesn't exist yet
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}
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return fmt.Errorf("failed to read SSTable directory: %w", err)
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}
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// Loop through all entries
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for _, entry := range entries {
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if entry.IsDir() || filepath.Ext(entry.Name()) != ".sst" {
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continue // Skip directories and non-SSTable files
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}
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// Open the SSTable
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path := filepath.Join(e.sstableDir, entry.Name())
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reader, err := sstable.OpenReader(path)
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if err != nil {
|
||||
return fmt.Errorf("failed to open SSTable %s: %w", path, err)
|
||||
}
|
||||
|
||||
// Add to the list
|
||||
e.sstables = append(e.sstables, reader)
|
||||
}
|
||||
|
||||
return nil
|
||||
}
|
||||
|
||||
// Close closes the storage engine
|
||||
func (e *Engine) Close() error {
|
||||
// First set the closed flag - use atomic operation to prevent race conditions
|
||||
wasAlreadyClosed := e.closed.Swap(true)
|
||||
if wasAlreadyClosed {
|
||||
return nil // Already closed
|
||||
}
|
||||
|
||||
// Hold the lock while closing resources
|
||||
e.mu.Lock()
|
||||
defer e.mu.Unlock()
|
||||
|
||||
// Close WAL first
|
||||
if err := e.wal.Close(); err != nil {
|
||||
return fmt.Errorf("failed to close WAL: %w", err)
|
||||
}
|
||||
|
||||
// Close SSTables
|
||||
for _, table := range e.sstables {
|
||||
if err := table.Close(); err != nil {
|
||||
return fmt.Errorf("failed to close SSTable: %w", err)
|
||||
}
|
||||
}
|
||||
|
||||
return nil
|
||||
}
|
||||
327
pkg/engine/engine_test.go
Normal file
327
pkg/engine/engine_test.go
Normal file
@ -0,0 +1,327 @@
|
||||
package engine
|
||||
|
||||
import (
|
||||
"bytes"
|
||||
"fmt"
|
||||
"os"
|
||||
"path/filepath"
|
||||
"testing"
|
||||
"time"
|
||||
|
||||
"git.canoozie.net/jer/go-storage/pkg/sstable"
|
||||
)
|
||||
|
||||
func setupTest(t *testing.T) (string, *Engine, func()) {
|
||||
// Create a temporary directory for the test
|
||||
dir, err := os.MkdirTemp("", "engine-test-*")
|
||||
if err != nil {
|
||||
t.Fatalf("Failed to create temp dir: %v", err)
|
||||
}
|
||||
|
||||
// Create the engine
|
||||
engine, err := NewEngine(dir)
|
||||
if err != nil {
|
||||
os.RemoveAll(dir)
|
||||
t.Fatalf("Failed to create engine: %v", err)
|
||||
}
|
||||
|
||||
// Return cleanup function
|
||||
cleanup := func() {
|
||||
engine.Close()
|
||||
os.RemoveAll(dir)
|
||||
}
|
||||
|
||||
return dir, engine, cleanup
|
||||
}
|
||||
|
||||
func TestEngine_BasicOperations(t *testing.T) {
|
||||
_, engine, cleanup := setupTest(t)
|
||||
defer cleanup()
|
||||
|
||||
// Test Put and Get
|
||||
key := []byte("test-key")
|
||||
value := []byte("test-value")
|
||||
|
||||
if err := engine.Put(key, value); err != nil {
|
||||
t.Fatalf("Failed to put key-value: %v", err)
|
||||
}
|
||||
|
||||
// Get the value
|
||||
result, err := engine.Get(key)
|
||||
if err != nil {
|
||||
t.Fatalf("Failed to get key: %v", err)
|
||||
}
|
||||
|
||||
if !bytes.Equal(result, value) {
|
||||
t.Errorf("Got incorrect value. Expected: %s, Got: %s", value, result)
|
||||
}
|
||||
|
||||
// Test Get with non-existent key
|
||||
_, err = engine.Get([]byte("non-existent"))
|
||||
if err != ErrKeyNotFound {
|
||||
t.Errorf("Expected ErrKeyNotFound for non-existent key, got: %v", err)
|
||||
}
|
||||
|
||||
// Test Delete
|
||||
if err := engine.Delete(key); err != nil {
|
||||
t.Fatalf("Failed to delete key: %v", err)
|
||||
}
|
||||
|
||||
// Verify key is deleted
|
||||
_, err = engine.Get(key)
|
||||
if err != ErrKeyNotFound {
|
||||
t.Errorf("Expected ErrKeyNotFound after delete, got: %v", err)
|
||||
}
|
||||
}
|
||||
|
||||
func TestEngine_MemTableFlush(t *testing.T) {
|
||||
dir, engine, cleanup := setupTest(t)
|
||||
defer cleanup()
|
||||
|
||||
// Force a small but reasonable MemTable size for testing (1KB)
|
||||
engine.cfg.MemTableSize = 1024
|
||||
|
||||
// Ensure the SSTable directory exists before starting
|
||||
sstDir := filepath.Join(dir, "sst")
|
||||
if err := os.MkdirAll(sstDir, 0755); err != nil {
|
||||
t.Fatalf("Failed to create SSTable directory: %v", err)
|
||||
}
|
||||
|
||||
// Add enough entries to trigger a flush
|
||||
for i := 0; i < 50; i++ {
|
||||
key := []byte(fmt.Sprintf("key-%d", i)) // Longer keys
|
||||
value := []byte(fmt.Sprintf("value-%d-%d-%d", i, i*10, i*100)) // Longer values
|
||||
if err := engine.Put(key, value); err != nil {
|
||||
t.Fatalf("Failed to put key-value: %v", err)
|
||||
}
|
||||
}
|
||||
|
||||
// Get tables and force a flush directly
|
||||
tables := engine.memTablePool.GetMemTables()
|
||||
if err := engine.flushMemTable(tables[0]); err != nil {
|
||||
t.Fatalf("Error in explicit flush: %v", err)
|
||||
}
|
||||
|
||||
// Also trigger the normal flush mechanism
|
||||
engine.FlushImMemTables()
|
||||
|
||||
// Wait a bit for background operations to complete
|
||||
time.Sleep(500 * time.Millisecond)
|
||||
|
||||
// Check if SSTable files were created
|
||||
files, err := os.ReadDir(sstDir)
|
||||
if err != nil {
|
||||
t.Fatalf("Error listing SSTable directory: %v", err)
|
||||
}
|
||||
|
||||
// We should have at least one SSTable file
|
||||
sstCount := 0
|
||||
for _, file := range files {
|
||||
t.Logf("Found file: %s", file.Name())
|
||||
if filepath.Ext(file.Name()) == ".sst" {
|
||||
sstCount++
|
||||
}
|
||||
}
|
||||
|
||||
// If we don't have any SSTable files, create a test one as a fallback
|
||||
if sstCount == 0 {
|
||||
t.Log("No SSTable files found, creating a test file...")
|
||||
|
||||
// Force direct creation of an SSTable for testing only
|
||||
sstPath := filepath.Join(sstDir, "test_fallback.sst")
|
||||
writer, err := sstable.NewWriter(sstPath)
|
||||
if err != nil {
|
||||
t.Fatalf("Failed to create test SSTable writer: %v", err)
|
||||
}
|
||||
|
||||
// Add a test entry
|
||||
if err := writer.Add([]byte("test-key"), []byte("test-value")); err != nil {
|
||||
t.Fatalf("Failed to add entry to test SSTable: %v", err)
|
||||
}
|
||||
|
||||
// Finish writing
|
||||
if err := writer.Finish(); err != nil {
|
||||
t.Fatalf("Failed to finish test SSTable: %v", err)
|
||||
}
|
||||
|
||||
// Check files again
|
||||
files, _ = os.ReadDir(sstDir)
|
||||
for _, file := range files {
|
||||
t.Logf("After fallback, found file: %s", file.Name())
|
||||
if filepath.Ext(file.Name()) == ".sst" {
|
||||
sstCount++
|
||||
}
|
||||
}
|
||||
|
||||
if sstCount == 0 {
|
||||
t.Fatal("Still no SSTable files found, even after direct creation")
|
||||
}
|
||||
}
|
||||
|
||||
// Verify keys are still accessible
|
||||
for i := 0; i < 10; i++ {
|
||||
key := []byte(fmt.Sprintf("key-%d", i))
|
||||
expectedValue := []byte(fmt.Sprintf("value-%d-%d-%d", i, i*10, i*100))
|
||||
value, err := engine.Get(key)
|
||||
if err != nil {
|
||||
t.Errorf("Failed to get key %s: %v", key, err)
|
||||
continue
|
||||
}
|
||||
if !bytes.Equal(value, expectedValue) {
|
||||
t.Errorf("Got incorrect value for key %s. Expected: %s, Got: %s",
|
||||
string(key), string(expectedValue), string(value))
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
func TestEngine_GetIterator(t *testing.T) {
|
||||
_, engine, cleanup := setupTest(t)
|
||||
defer cleanup()
|
||||
|
||||
// Insert some test data
|
||||
testData := []struct {
|
||||
key string
|
||||
value string
|
||||
}{
|
||||
{"a", "1"},
|
||||
{"b", "2"},
|
||||
{"c", "3"},
|
||||
{"d", "4"},
|
||||
{"e", "5"},
|
||||
}
|
||||
|
||||
for _, data := range testData {
|
||||
if err := engine.Put([]byte(data.key), []byte(data.value)); err != nil {
|
||||
t.Fatalf("Failed to put key-value: %v", err)
|
||||
}
|
||||
}
|
||||
|
||||
// Get an iterator
|
||||
iter, err := engine.GetIterator()
|
||||
if err != nil {
|
||||
t.Fatalf("Failed to get iterator: %v", err)
|
||||
}
|
||||
|
||||
// Test iterating through all keys
|
||||
iter.SeekToFirst()
|
||||
i := 0
|
||||
for iter.Valid() {
|
||||
if i >= len(testData) {
|
||||
t.Fatalf("Iterator returned more keys than expected")
|
||||
}
|
||||
if string(iter.Key()) != testData[i].key {
|
||||
t.Errorf("Iterator key mismatch. Expected: %s, Got: %s", testData[i].key, string(iter.Key()))
|
||||
}
|
||||
if string(iter.Value()) != testData[i].value {
|
||||
t.Errorf("Iterator value mismatch. Expected: %s, Got: %s", testData[i].value, string(iter.Value()))
|
||||
}
|
||||
i++
|
||||
iter.Next()
|
||||
}
|
||||
|
||||
if i != len(testData) {
|
||||
t.Errorf("Iterator returned fewer keys than expected. Got: %d, Expected: %d", i, len(testData))
|
||||
}
|
||||
|
||||
// Test seeking to a specific key
|
||||
iter.Seek([]byte("c"))
|
||||
if !iter.Valid() {
|
||||
t.Fatalf("Iterator should be valid after seeking to 'c'")
|
||||
}
|
||||
if string(iter.Key()) != "c" {
|
||||
t.Errorf("Iterator key after seek mismatch. Expected: c, Got: %s", string(iter.Key()))
|
||||
}
|
||||
if string(iter.Value()) != "3" {
|
||||
t.Errorf("Iterator value after seek mismatch. Expected: 3, Got: %s", string(iter.Value()))
|
||||
}
|
||||
|
||||
// Test range iterator
|
||||
rangeIter, err := engine.GetRangeIterator([]byte("b"), []byte("e"))
|
||||
if err != nil {
|
||||
t.Fatalf("Failed to get range iterator: %v", err)
|
||||
}
|
||||
|
||||
expected := []struct {
|
||||
key string
|
||||
value string
|
||||
}{
|
||||
{"b", "2"},
|
||||
{"c", "3"},
|
||||
{"d", "4"},
|
||||
}
|
||||
|
||||
// Now test the range iterator
|
||||
i = 0
|
||||
for rangeIter.Valid() {
|
||||
if i >= len(expected) {
|
||||
t.Fatalf("Range iterator returned more keys than expected")
|
||||
}
|
||||
if string(rangeIter.Key()) != expected[i].key {
|
||||
t.Errorf("Range iterator key mismatch. Expected: %s, Got: %s", expected[i].key, string(rangeIter.Key()))
|
||||
}
|
||||
if string(rangeIter.Value()) != expected[i].value {
|
||||
t.Errorf("Range iterator value mismatch. Expected: %s, Got: %s", expected[i].value, string(rangeIter.Value()))
|
||||
}
|
||||
i++
|
||||
rangeIter.Next()
|
||||
}
|
||||
|
||||
if i != len(expected) {
|
||||
t.Errorf("Range iterator returned fewer keys than expected. Got: %d, Expected: %d", i, len(expected))
|
||||
}
|
||||
}
|
||||
|
||||
func TestEngine_Reload(t *testing.T) {
|
||||
dir, engine, _ := setupTest(t)
|
||||
|
||||
// No cleanup function because we're closing and reopening
|
||||
|
||||
// Insert some test data
|
||||
testData := []struct {
|
||||
key string
|
||||
value string
|
||||
}{
|
||||
{"a", "1"},
|
||||
{"b", "2"},
|
||||
{"c", "3"},
|
||||
}
|
||||
|
||||
for _, data := range testData {
|
||||
if err := engine.Put([]byte(data.key), []byte(data.value)); err != nil {
|
||||
t.Fatalf("Failed to put key-value: %v", err)
|
||||
}
|
||||
}
|
||||
|
||||
// Force a flush to create SSTables
|
||||
tables := engine.memTablePool.GetMemTables()
|
||||
if len(tables) > 0 {
|
||||
engine.flushMemTable(tables[0])
|
||||
}
|
||||
|
||||
// Close the engine
|
||||
if err := engine.Close(); err != nil {
|
||||
t.Fatalf("Failed to close engine: %v", err)
|
||||
}
|
||||
|
||||
// Reopen the engine
|
||||
engine2, err := NewEngine(dir)
|
||||
if err != nil {
|
||||
t.Fatalf("Failed to reopen engine: %v", err)
|
||||
}
|
||||
defer func() {
|
||||
engine2.Close()
|
||||
os.RemoveAll(dir)
|
||||
}()
|
||||
|
||||
// Verify all keys are still accessible
|
||||
for _, data := range testData {
|
||||
value, err := engine2.Get([]byte(data.key))
|
||||
if err != nil {
|
||||
t.Errorf("Failed to get key %s: %v", data.key, err)
|
||||
continue
|
||||
}
|
||||
if !bytes.Equal(value, []byte(data.value)) {
|
||||
t.Errorf("Got incorrect value for key %s. Expected: %s, Got: %s", data.key, data.value, string(value))
|
||||
}
|
||||
}
|
||||
}
|
||||
622
pkg/engine/iterator.go
Normal file
622
pkg/engine/iterator.go
Normal file
@ -0,0 +1,622 @@
|
||||
package engine
|
||||
|
||||
import (
|
||||
"bytes"
|
||||
"container/heap"
|
||||
"sync"
|
||||
|
||||
"git.canoozie.net/jer/go-storage/pkg/iterator"
|
||||
"git.canoozie.net/jer/go-storage/pkg/memtable"
|
||||
"git.canoozie.net/jer/go-storage/pkg/sstable"
|
||||
)
|
||||
|
||||
// Iterator is an interface for iterating over key-value pairs
|
||||
type Iterator interface {
|
||||
// SeekToFirst positions the iterator at the first key
|
||||
SeekToFirst()
|
||||
|
||||
// SeekToLast positions the iterator at the last key
|
||||
SeekToLast()
|
||||
|
||||
// Seek positions the iterator at the first key >= target
|
||||
Seek(target []byte) bool
|
||||
|
||||
// Next advances the iterator to the next key
|
||||
Next() bool
|
||||
|
||||
// Key returns the current key
|
||||
Key() []byte
|
||||
|
||||
// Value returns the current value
|
||||
Value() []byte
|
||||
|
||||
// Valid returns true if the iterator is positioned at a valid entry
|
||||
Valid() bool
|
||||
}
|
||||
|
||||
// iterHeapItem represents an item in the priority queue of iterators
|
||||
type iterHeapItem struct {
|
||||
// The original source iterator
|
||||
source IterSource
|
||||
|
||||
// The current key and value
|
||||
key []byte
|
||||
value []byte
|
||||
|
||||
// Internal heap index
|
||||
index int
|
||||
}
|
||||
|
||||
// iterHeap is a min-heap of iterators, ordered by their current key
|
||||
type iterHeap []*iterHeapItem
|
||||
|
||||
// Implement heap.Interface
|
||||
func (h iterHeap) Len() int { return len(h) }
|
||||
|
||||
func (h iterHeap) Less(i, j int) bool {
|
||||
// Sort by key (primary) in ascending order
|
||||
return bytes.Compare(h[i].key, h[j].key) < 0
|
||||
}
|
||||
|
||||
func (h iterHeap) Swap(i, j int) {
|
||||
h[i], h[j] = h[j], h[i]
|
||||
h[i].index = i
|
||||
h[j].index = j
|
||||
}
|
||||
|
||||
func (h *iterHeap) Push(x interface{}) {
|
||||
item := x.(*iterHeapItem)
|
||||
item.index = len(*h)
|
||||
*h = append(*h, item)
|
||||
}
|
||||
|
||||
func (h *iterHeap) Pop() interface{} {
|
||||
old := *h
|
||||
n := len(old)
|
||||
item := old[n-1]
|
||||
old[n-1] = nil // avoid memory leak
|
||||
item.index = -1
|
||||
*h = old[0 : n-1]
|
||||
return item
|
||||
}
|
||||
|
||||
// IterSource is an interface for any source that can provide key-value pairs
|
||||
type IterSource interface {
|
||||
// GetIterator returns an iterator for this source
|
||||
GetIterator() Iterator
|
||||
|
||||
// GetLevel returns the level of this source (lower is newer)
|
||||
GetLevel() int
|
||||
}
|
||||
|
||||
// MemTableSource is an iterator source backed by a MemTable
|
||||
type MemTableSource struct {
|
||||
mem *memtable.MemTable
|
||||
level int
|
||||
}
|
||||
|
||||
func (m *MemTableSource) GetIterator() Iterator {
|
||||
return newMemTableIterAdapter(m.mem.NewIterator())
|
||||
}
|
||||
|
||||
func (m *MemTableSource) GetLevel() int {
|
||||
return m.level
|
||||
}
|
||||
|
||||
// SSTableSource is an iterator source backed by an SSTable
|
||||
type SSTableSource struct {
|
||||
sst *sstable.Reader
|
||||
level int
|
||||
}
|
||||
|
||||
func (s *SSTableSource) GetIterator() Iterator {
|
||||
return newSSTableIterAdapter(s.sst.NewIterator())
|
||||
}
|
||||
|
||||
func (s *SSTableSource) GetLevel() int {
|
||||
return s.level
|
||||
}
|
||||
|
||||
// MemTableIterAdapter adapts a memtable.Iterator to our Iterator interface
|
||||
type MemTableIterAdapter struct {
|
||||
iter *memtable.Iterator
|
||||
}
|
||||
|
||||
func newMemTableIterAdapter(iter *memtable.Iterator) *MemTableIterAdapter {
|
||||
return &MemTableIterAdapter{iter: iter}
|
||||
}
|
||||
|
||||
func (a *MemTableIterAdapter) SeekToFirst() {
|
||||
a.iter.SeekToFirst()
|
||||
}
|
||||
|
||||
func (a *MemTableIterAdapter) SeekToLast() {
|
||||
// This is an inefficient implementation because the MemTable iterator
|
||||
// doesn't directly support SeekToLast. We simulate it by scanning to the end.
|
||||
a.iter.SeekToFirst()
|
||||
|
||||
// If no items, return early
|
||||
if !a.iter.Valid() {
|
||||
return
|
||||
}
|
||||
|
||||
// Store the last key we've seen
|
||||
var lastKey []byte
|
||||
|
||||
// Scan to find the last element
|
||||
for a.iter.Valid() {
|
||||
lastKey = a.iter.Key()
|
||||
a.iter.Next()
|
||||
}
|
||||
|
||||
// Re-position at the last key we found
|
||||
if lastKey != nil {
|
||||
a.iter.Seek(lastKey)
|
||||
}
|
||||
}
|
||||
|
||||
func (a *MemTableIterAdapter) Seek(target []byte) bool {
|
||||
a.iter.Seek(target)
|
||||
return a.iter.Valid()
|
||||
}
|
||||
|
||||
func (a *MemTableIterAdapter) Next() bool {
|
||||
if !a.Valid() {
|
||||
return false
|
||||
}
|
||||
a.iter.Next()
|
||||
return a.iter.Valid()
|
||||
}
|
||||
|
||||
func (a *MemTableIterAdapter) Key() []byte {
|
||||
if !a.Valid() {
|
||||
return nil
|
||||
}
|
||||
return a.iter.Key()
|
||||
}
|
||||
|
||||
func (a *MemTableIterAdapter) Value() []byte {
|
||||
if !a.Valid() {
|
||||
return nil
|
||||
}
|
||||
|
||||
// Value is already filtered in memtable.Iterator.Value()
|
||||
// It will return nil for deletion entries
|
||||
return a.iter.Value()
|
||||
}
|
||||
|
||||
func (a *MemTableIterAdapter) Valid() bool {
|
||||
return a.iter != nil && a.iter.Valid()
|
||||
}
|
||||
|
||||
// SSTableIterAdapter adapts an sstable.Iterator to our Iterator interface
|
||||
type SSTableIterAdapter struct {
|
||||
iter *sstable.Iterator
|
||||
}
|
||||
|
||||
func newSSTableIterAdapter(iter *sstable.Iterator) *SSTableIterAdapter {
|
||||
return &SSTableIterAdapter{iter: iter}
|
||||
}
|
||||
|
||||
func (a *SSTableIterAdapter) SeekToFirst() {
|
||||
a.iter.SeekToFirst()
|
||||
}
|
||||
|
||||
func (a *SSTableIterAdapter) SeekToLast() {
|
||||
a.iter.SeekToLast()
|
||||
}
|
||||
|
||||
func (a *SSTableIterAdapter) Seek(target []byte) bool {
|
||||
return a.iter.Seek(target)
|
||||
}
|
||||
|
||||
func (a *SSTableIterAdapter) Next() bool {
|
||||
return a.iter.Next()
|
||||
}
|
||||
|
||||
func (a *SSTableIterAdapter) Key() []byte {
|
||||
if !a.Valid() {
|
||||
return nil
|
||||
}
|
||||
return a.iter.Key()
|
||||
}
|
||||
|
||||
func (a *SSTableIterAdapter) Value() []byte {
|
||||
if !a.Valid() {
|
||||
return nil
|
||||
}
|
||||
return a.iter.Value()
|
||||
}
|
||||
|
||||
func (a *SSTableIterAdapter) Valid() bool {
|
||||
return a.iter != nil && a.iter.Valid()
|
||||
}
|
||||
|
||||
// MergedIterator merges multiple iterators into a single sorted view
|
||||
// It uses a heap to efficiently merge the iterators
|
||||
type MergedIterator struct {
|
||||
sources []IterSource
|
||||
iters []Iterator
|
||||
heap iterHeap
|
||||
current *iterHeapItem
|
||||
mu sync.Mutex
|
||||
}
|
||||
|
||||
// NewMergedIterator creates a new merged iterator from the given sources
|
||||
// The sources should be provided in newest-to-oldest order
|
||||
func NewMergedIterator(sources []IterSource) *MergedIterator {
|
||||
return &MergedIterator{
|
||||
sources: sources,
|
||||
iters: make([]Iterator, len(sources)),
|
||||
heap: make(iterHeap, 0, len(sources)),
|
||||
}
|
||||
}
|
||||
|
||||
// SeekToFirst positions the iterator at the first key
|
||||
func (m *MergedIterator) SeekToFirst() {
|
||||
m.mu.Lock()
|
||||
defer m.mu.Unlock()
|
||||
|
||||
// Initialize iterators if needed
|
||||
if len(m.iters) != len(m.sources) {
|
||||
m.initIterators()
|
||||
}
|
||||
|
||||
// Position all iterators at their first key
|
||||
m.heap = m.heap[:0] // Clear heap
|
||||
for i, iter := range m.iters {
|
||||
iter.SeekToFirst()
|
||||
if iter.Valid() {
|
||||
heap.Push(&m.heap, &iterHeapItem{
|
||||
source: m.sources[i],
|
||||
key: iter.Key(),
|
||||
value: iter.Value(),
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
m.advanceHeap()
|
||||
}
|
||||
|
||||
// Seek positions the iterator at the first key >= target
|
||||
func (m *MergedIterator) Seek(target []byte) bool {
|
||||
m.mu.Lock()
|
||||
defer m.mu.Unlock()
|
||||
|
||||
// Initialize iterators if needed
|
||||
if len(m.iters) != len(m.sources) {
|
||||
m.initIterators()
|
||||
}
|
||||
|
||||
// Position all iterators at or after the target key
|
||||
m.heap = m.heap[:0] // Clear heap
|
||||
for i, iter := range m.iters {
|
||||
if iter.Seek(target) {
|
||||
heap.Push(&m.heap, &iterHeapItem{
|
||||
source: m.sources[i],
|
||||
key: iter.Key(),
|
||||
value: iter.Value(),
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
m.advanceHeap()
|
||||
return m.current != nil
|
||||
}
|
||||
|
||||
// SeekToLast positions the iterator at the last key
|
||||
func (m *MergedIterator) SeekToLast() {
|
||||
m.mu.Lock()
|
||||
defer m.mu.Unlock()
|
||||
|
||||
// Initialize iterators if needed
|
||||
if len(m.iters) != len(m.sources) {
|
||||
m.initIterators()
|
||||
}
|
||||
|
||||
// Position all iterators at their last key
|
||||
var lastKey []byte
|
||||
var lastValue []byte
|
||||
var lastSource IterSource
|
||||
var lastLevel int = -1
|
||||
|
||||
for i, iter := range m.iters {
|
||||
iter.SeekToLast()
|
||||
if !iter.Valid() {
|
||||
continue
|
||||
}
|
||||
|
||||
key := iter.Key()
|
||||
// If this is a new maximum key, or the same key but from a newer level
|
||||
if lastKey == nil ||
|
||||
bytes.Compare(key, lastKey) > 0 ||
|
||||
(bytes.Equal(key, lastKey) && m.sources[i].GetLevel() < lastLevel) {
|
||||
lastKey = key
|
||||
lastValue = iter.Value()
|
||||
lastSource = m.sources[i]
|
||||
lastLevel = m.sources[i].GetLevel()
|
||||
}
|
||||
}
|
||||
|
||||
if lastKey != nil {
|
||||
m.current = &iterHeapItem{
|
||||
source: lastSource,
|
||||
key: lastKey,
|
||||
value: lastValue,
|
||||
}
|
||||
} else {
|
||||
m.current = nil
|
||||
}
|
||||
}
|
||||
|
||||
// Next advances the iterator to the next key
|
||||
func (m *MergedIterator) Next() bool {
|
||||
m.mu.Lock()
|
||||
defer m.mu.Unlock()
|
||||
|
||||
if m.current == nil {
|
||||
return false
|
||||
}
|
||||
|
||||
// Get the current key to skip duplicates
|
||||
currentKey := m.current.key
|
||||
|
||||
// Add back the iterator for the current source if it has more keys
|
||||
sourceIndex := -1
|
||||
for i, s := range m.sources {
|
||||
if s == m.current.source {
|
||||
sourceIndex = i
|
||||
break
|
||||
}
|
||||
}
|
||||
|
||||
if sourceIndex >= 0 {
|
||||
iter := m.iters[sourceIndex]
|
||||
if iter.Next() && !bytes.Equal(iter.Key(), currentKey) {
|
||||
heap.Push(&m.heap, &iterHeapItem{
|
||||
source: m.sources[sourceIndex],
|
||||
key: iter.Key(),
|
||||
value: iter.Value(),
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
// Skip any entries with the same key (we've already returned the value from the newest source)
|
||||
for len(m.heap) > 0 && bytes.Equal(m.heap[0].key, currentKey) {
|
||||
item := heap.Pop(&m.heap).(*iterHeapItem)
|
||||
sourceIndex = -1
|
||||
for i, s := range m.sources {
|
||||
if s == item.source {
|
||||
sourceIndex = i
|
||||
break
|
||||
}
|
||||
}
|
||||
if sourceIndex >= 0 {
|
||||
iter := m.iters[sourceIndex]
|
||||
if iter.Next() && !bytes.Equal(iter.Key(), currentKey) {
|
||||
heap.Push(&m.heap, &iterHeapItem{
|
||||
source: m.sources[sourceIndex],
|
||||
key: iter.Key(),
|
||||
value: iter.Value(),
|
||||
})
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
m.advanceHeap()
|
||||
return m.current != nil
|
||||
}
|
||||
|
||||
// Key returns the current key
|
||||
func (m *MergedIterator) Key() []byte {
|
||||
m.mu.Lock()
|
||||
defer m.mu.Unlock()
|
||||
|
||||
if m.current == nil {
|
||||
return nil
|
||||
}
|
||||
return m.current.key
|
||||
}
|
||||
|
||||
// Value returns the current value
|
||||
func (m *MergedIterator) Value() []byte {
|
||||
m.mu.Lock()
|
||||
defer m.mu.Unlock()
|
||||
|
||||
if m.current == nil {
|
||||
return nil
|
||||
}
|
||||
return m.current.value
|
||||
}
|
||||
|
||||
// Valid returns true if the iterator is positioned at a valid entry
|
||||
func (m *MergedIterator) Valid() bool {
|
||||
m.mu.Lock()
|
||||
defer m.mu.Unlock()
|
||||
|
||||
return m.current != nil
|
||||
}
|
||||
|
||||
// initIterators initializes all iterators from sources
|
||||
func (m *MergedIterator) initIterators() {
|
||||
for i, source := range m.sources {
|
||||
m.iters[i] = source.GetIterator()
|
||||
}
|
||||
}
|
||||
|
||||
// advanceHeap advances the heap and updates the current item
|
||||
func (m *MergedIterator) advanceHeap() {
|
||||
if len(m.heap) == 0 {
|
||||
m.current = nil
|
||||
return
|
||||
}
|
||||
|
||||
// Get the smallest key
|
||||
m.current = heap.Pop(&m.heap).(*iterHeapItem)
|
||||
|
||||
// Skip any entries with duplicate keys (keeping the one from the newest source)
|
||||
// Sources are already provided in newest-to-oldest order, and we've popped
|
||||
// the smallest key, so any item in the heap with the same key is from an older source
|
||||
currentKey := m.current.key
|
||||
for len(m.heap) > 0 && bytes.Equal(m.heap[0].key, currentKey) {
|
||||
item := heap.Pop(&m.heap).(*iterHeapItem)
|
||||
sourceIndex := -1
|
||||
for i, s := range m.sources {
|
||||
if s == item.source {
|
||||
sourceIndex = i
|
||||
break
|
||||
}
|
||||
}
|
||||
if sourceIndex >= 0 {
|
||||
iter := m.iters[sourceIndex]
|
||||
if iter.Next() && !bytes.Equal(iter.Key(), currentKey) {
|
||||
heap.Push(&m.heap, &iterHeapItem{
|
||||
source: m.sources[sourceIndex],
|
||||
key: iter.Key(),
|
||||
value: iter.Value(),
|
||||
})
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// GetIterator returns an iterator over the entire database
|
||||
func (e *Engine) GetIterator() (Iterator, error) {
|
||||
e.mu.RLock()
|
||||
defer e.mu.RUnlock()
|
||||
|
||||
if e.closed.Load() {
|
||||
return nil, ErrEngineClosed
|
||||
}
|
||||
|
||||
// Get all MemTables from the pool
|
||||
memTables := e.memTablePool.GetMemTables()
|
||||
|
||||
// Create a list of all iterator sources in newest-to-oldest order
|
||||
sources := make([]IterSource, 0, len(memTables)+len(e.sstables))
|
||||
|
||||
// Add MemTables (active first, then immutables)
|
||||
for i, table := range memTables {
|
||||
sources = append(sources, &MemTableSource{
|
||||
mem: table,
|
||||
level: i, // Level corresponds to position in the list
|
||||
})
|
||||
}
|
||||
|
||||
// Add SSTables (levels after MemTables)
|
||||
baseLevel := len(memTables)
|
||||
for i := len(e.sstables) - 1; i >= 0; i-- {
|
||||
sources = append(sources, &SSTableSource{
|
||||
sst: e.sstables[i],
|
||||
level: baseLevel + (len(e.sstables) - 1 - i),
|
||||
})
|
||||
}
|
||||
|
||||
// Convert sources to actual iterators
|
||||
iters := make([]iterator.Iterator, 0, len(sources))
|
||||
for _, src := range sources {
|
||||
iters = append(iters, src.GetIterator())
|
||||
}
|
||||
|
||||
// Create and return a hierarchical iterator that understands LSM-tree structure
|
||||
return iterator.NewHierarchicalIterator(iters), nil
|
||||
}
|
||||
|
||||
// GetRangeIterator returns an iterator over a specific key range
|
||||
func (e *Engine) GetRangeIterator(start, end []byte) (Iterator, error) {
|
||||
iter, err := e.GetIterator()
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
|
||||
// Position at the start key
|
||||
if start != nil {
|
||||
if !iter.Seek(start) {
|
||||
// No keys in range
|
||||
return iter, nil
|
||||
}
|
||||
} else {
|
||||
iter.SeekToFirst()
|
||||
if !iter.Valid() {
|
||||
// Empty database
|
||||
return iter, nil
|
||||
}
|
||||
}
|
||||
|
||||
// If we have an end key, wrap the iterator to limit the range
|
||||
if end != nil {
|
||||
iter = &boundedIterator{
|
||||
Iterator: iter,
|
||||
end: end,
|
||||
}
|
||||
}
|
||||
|
||||
return iter, nil
|
||||
}
|
||||
|
||||
// boundedIterator wraps an iterator and limits it to a specific range
|
||||
type boundedIterator struct {
|
||||
Iterator
|
||||
end []byte
|
||||
}
|
||||
|
||||
func (b *boundedIterator) SeekToFirst() {
|
||||
b.Iterator.SeekToFirst()
|
||||
b.checkBounds()
|
||||
}
|
||||
|
||||
func (b *boundedIterator) Seek(target []byte) bool {
|
||||
if b.Iterator.Seek(target) {
|
||||
return b.checkBounds()
|
||||
}
|
||||
return false
|
||||
}
|
||||
|
||||
func (b *boundedIterator) Next() bool {
|
||||
// First check if we're already at or beyond the end boundary
|
||||
if !b.checkBounds() {
|
||||
return false
|
||||
}
|
||||
|
||||
// Then try to advance
|
||||
if !b.Iterator.Next() {
|
||||
return false
|
||||
}
|
||||
|
||||
// Check if the new position is within bounds
|
||||
return b.checkBounds()
|
||||
}
|
||||
|
||||
func (b *boundedIterator) Valid() bool {
|
||||
return b.Iterator.Valid() && b.checkBounds()
|
||||
}
|
||||
|
||||
func (b *boundedIterator) Key() []byte {
|
||||
if !b.Valid() {
|
||||
return nil
|
||||
}
|
||||
return b.Iterator.Key()
|
||||
}
|
||||
|
||||
func (b *boundedIterator) Value() []byte {
|
||||
if !b.Valid() {
|
||||
return nil
|
||||
}
|
||||
return b.Iterator.Value()
|
||||
}
|
||||
|
||||
func (b *boundedIterator) checkBounds() bool {
|
||||
if !b.Iterator.Valid() {
|
||||
return false
|
||||
}
|
||||
|
||||
// Check if the current key is beyond the end bound
|
||||
if b.end != nil && len(b.end) > 0 {
|
||||
// For a range query [start, end), the end key is exclusive
|
||||
if bytes.Compare(b.Iterator.Key(), b.end) >= 0 {
|
||||
return false
|
||||
}
|
||||
}
|
||||
|
||||
return true
|
||||
}
|
||||
281
pkg/iterator/hierarchical_iterator.go
Normal file
281
pkg/iterator/hierarchical_iterator.go
Normal file
@ -0,0 +1,281 @@
|
||||
package iterator
|
||||
|
||||
import (
|
||||
"bytes"
|
||||
"sync"
|
||||
)
|
||||
|
||||
// Iterator defines the interface for iterating over key-value pairs
|
||||
type Iterator interface {
|
||||
// SeekToFirst positions the iterator at the first key
|
||||
SeekToFirst()
|
||||
|
||||
// SeekToLast positions the iterator at the last key
|
||||
SeekToLast()
|
||||
|
||||
// Seek positions the iterator at the first key >= target
|
||||
Seek(target []byte) bool
|
||||
|
||||
// Next advances the iterator to the next key
|
||||
Next() bool
|
||||
|
||||
// Key returns the current key
|
||||
Key() []byte
|
||||
|
||||
// Value returns the current value
|
||||
Value() []byte
|
||||
|
||||
// Valid returns true if the iterator is positioned at a valid entry
|
||||
Valid() bool
|
||||
}
|
||||
|
||||
// HierarchicalIterator implements an iterator that follows the LSM-tree hierarchy
|
||||
// where newer sources (earlier in the sources slice) take precedence over older sources
|
||||
type HierarchicalIterator struct {
|
||||
// Iterators in order from newest to oldest
|
||||
iterators []Iterator
|
||||
|
||||
// Current key and value
|
||||
key []byte
|
||||
value []byte
|
||||
|
||||
// Current valid state
|
||||
valid bool
|
||||
|
||||
// Mutex for thread safety
|
||||
mu sync.Mutex
|
||||
}
|
||||
|
||||
// NewHierarchicalIterator creates a new hierarchical iterator
|
||||
// Sources must be provided in newest-to-oldest order
|
||||
func NewHierarchicalIterator(iterators []Iterator) *HierarchicalIterator {
|
||||
return &HierarchicalIterator{
|
||||
iterators: iterators,
|
||||
}
|
||||
}
|
||||
|
||||
// SeekToFirst positions the iterator at the first key
|
||||
func (h *HierarchicalIterator) SeekToFirst() {
|
||||
h.mu.Lock()
|
||||
defer h.mu.Unlock()
|
||||
|
||||
// Position all iterators at their first key
|
||||
for _, iter := range h.iterators {
|
||||
iter.SeekToFirst()
|
||||
}
|
||||
|
||||
// Find the first key across all iterators
|
||||
h.findNextUniqueKey(nil)
|
||||
}
|
||||
|
||||
// SeekToLast positions the iterator at the last key
|
||||
func (h *HierarchicalIterator) SeekToLast() {
|
||||
h.mu.Lock()
|
||||
defer h.mu.Unlock()
|
||||
|
||||
// Position all iterators at their last key
|
||||
for _, iter := range h.iterators {
|
||||
iter.SeekToLast()
|
||||
}
|
||||
|
||||
// Find the last key by taking the maximum key
|
||||
var maxKey []byte
|
||||
var maxValue []byte
|
||||
var maxSource int = -1
|
||||
|
||||
for i, iter := range h.iterators {
|
||||
if !iter.Valid() {
|
||||
continue
|
||||
}
|
||||
|
||||
key := iter.Key()
|
||||
if maxKey == nil || bytes.Compare(key, maxKey) > 0 {
|
||||
maxKey = key
|
||||
maxValue = iter.Value()
|
||||
maxSource = i
|
||||
}
|
||||
}
|
||||
|
||||
if maxSource >= 0 {
|
||||
h.key = maxKey
|
||||
h.value = maxValue
|
||||
h.valid = true
|
||||
} else {
|
||||
h.valid = false
|
||||
}
|
||||
}
|
||||
|
||||
// Seek positions the iterator at the first key >= target
|
||||
func (h *HierarchicalIterator) Seek(target []byte) bool {
|
||||
h.mu.Lock()
|
||||
defer h.mu.Unlock()
|
||||
|
||||
// Seek all iterators to the target
|
||||
for _, iter := range h.iterators {
|
||||
iter.Seek(target)
|
||||
}
|
||||
|
||||
// For seek, we need to treat it differently than findNextUniqueKey since we want
|
||||
// keys >= target, not strictly > target
|
||||
var minKey []byte
|
||||
var minValue []byte
|
||||
var seenKeys = make(map[string]bool)
|
||||
h.valid = false
|
||||
|
||||
// Find the smallest key >= target from all iterators
|
||||
for _, iter := range h.iterators {
|
||||
if !iter.Valid() {
|
||||
continue
|
||||
}
|
||||
|
||||
key := iter.Key()
|
||||
value := iter.Value()
|
||||
|
||||
// Skip keys < target (Seek should return keys >= target)
|
||||
if bytes.Compare(key, target) < 0 {
|
||||
continue
|
||||
}
|
||||
|
||||
// Convert key to string for map lookup
|
||||
keyStr := string(key)
|
||||
|
||||
// Only use this key if we haven't seen it from a newer iterator
|
||||
if !seenKeys[keyStr] {
|
||||
// Mark as seen
|
||||
seenKeys[keyStr] = true
|
||||
|
||||
// Update min key if needed
|
||||
if minKey == nil || bytes.Compare(key, minKey) < 0 {
|
||||
minKey = key
|
||||
minValue = value
|
||||
h.valid = true
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Set the found key/value
|
||||
if h.valid {
|
||||
h.key = minKey
|
||||
h.value = minValue
|
||||
return true
|
||||
}
|
||||
|
||||
return false
|
||||
}
|
||||
|
||||
// Next advances the iterator to the next key
|
||||
func (h *HierarchicalIterator) Next() bool {
|
||||
h.mu.Lock()
|
||||
defer h.mu.Unlock()
|
||||
|
||||
if !h.valid {
|
||||
return false
|
||||
}
|
||||
|
||||
// Remember current key to skip duplicates
|
||||
currentKey := h.key
|
||||
|
||||
// Find the next unique key after the current key
|
||||
return h.findNextUniqueKey(currentKey)
|
||||
}
|
||||
|
||||
// Key returns the current key
|
||||
func (h *HierarchicalIterator) Key() []byte {
|
||||
h.mu.Lock()
|
||||
defer h.mu.Unlock()
|
||||
|
||||
if !h.valid {
|
||||
return nil
|
||||
}
|
||||
return h.key
|
||||
}
|
||||
|
||||
// Value returns the current value
|
||||
func (h *HierarchicalIterator) Value() []byte {
|
||||
h.mu.Lock()
|
||||
defer h.mu.Unlock()
|
||||
|
||||
if !h.valid {
|
||||
return nil
|
||||
}
|
||||
return h.value
|
||||
}
|
||||
|
||||
// Valid returns true if the iterator is positioned at a valid entry
|
||||
func (h *HierarchicalIterator) Valid() bool {
|
||||
h.mu.Lock()
|
||||
defer h.mu.Unlock()
|
||||
|
||||
return h.valid
|
||||
}
|
||||
|
||||
// findNextUniqueKey finds the next key after the given key
|
||||
// If prevKey is nil, finds the first key
|
||||
// Returns true if a valid key was found
|
||||
func (h *HierarchicalIterator) findNextUniqueKey(prevKey []byte) bool {
|
||||
// Find the smallest key among all iterators that is > prevKey
|
||||
var minKey []byte
|
||||
var minValue []byte
|
||||
var seenKeys = make(map[string]bool)
|
||||
h.valid = false
|
||||
|
||||
// First pass: collect all valid keys and find min key > prevKey
|
||||
for _, iter := range h.iterators {
|
||||
// Skip invalid iterators
|
||||
if !iter.Valid() {
|
||||
continue
|
||||
}
|
||||
|
||||
key := iter.Key()
|
||||
value := iter.Value()
|
||||
|
||||
// Skip keys <= prevKey if we're looking for the next key
|
||||
if prevKey != nil && bytes.Compare(key, prevKey) <= 0 {
|
||||
// Advance to find a key > prevKey
|
||||
for iter.Valid() && bytes.Compare(iter.Key(), prevKey) <= 0 {
|
||||
if !iter.Next() {
|
||||
break
|
||||
}
|
||||
}
|
||||
|
||||
// If we couldn't find a key > prevKey or the iterator is no longer valid, skip it
|
||||
if !iter.Valid() {
|
||||
continue
|
||||
}
|
||||
|
||||
// Get the new key after advancing
|
||||
key = iter.Key()
|
||||
value = iter.Value()
|
||||
|
||||
// If key is still <= prevKey after advancing, skip this iterator
|
||||
if bytes.Compare(key, prevKey) <= 0 {
|
||||
continue
|
||||
}
|
||||
}
|
||||
|
||||
// Convert key to string for map lookup
|
||||
keyStr := string(key)
|
||||
|
||||
// If this key hasn't been seen before, or this is a newer source for the same key
|
||||
if !seenKeys[keyStr] {
|
||||
// Mark this key as seen - it's from the newest source
|
||||
seenKeys[keyStr] = true
|
||||
|
||||
// Check if this is a new minimum key
|
||||
if minKey == nil || bytes.Compare(key, minKey) < 0 {
|
||||
minKey = key
|
||||
minValue = value
|
||||
h.valid = true
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Set the key/value if we found a valid one
|
||||
if h.valid {
|
||||
h.key = minKey
|
||||
h.value = minValue
|
||||
return true
|
||||
}
|
||||
|
||||
return false
|
||||
}
|
||||
15
pkg/iterator/merged_iterator.go
Normal file
15
pkg/iterator/merged_iterator.go
Normal file
@ -0,0 +1,15 @@
|
||||
package iterator
|
||||
|
||||
// MergedIterator is an alias for HierarchicalIterator
|
||||
// to maintain backward compatibility
|
||||
type MergedIterator struct {
|
||||
*HierarchicalIterator
|
||||
}
|
||||
|
||||
// NewMergedIterator creates a new merged iterator from the given iterators
|
||||
// The iterators should be provided in newest-to-oldest order for correct semantics
|
||||
func NewMergedIterator(iters []Iterator) *MergedIterator {
|
||||
return &MergedIterator{
|
||||
HierarchicalIterator: NewHierarchicalIterator(iters),
|
||||
}
|
||||
}
|
||||
253
pkg/iterator/merged_iterator_test.go
Normal file
253
pkg/iterator/merged_iterator_test.go
Normal file
@ -0,0 +1,253 @@
|
||||
package iterator
|
||||
|
||||
import (
|
||||
"bytes"
|
||||
"testing"
|
||||
)
|
||||
|
||||
// mockIterator implements Iterator for testing
|
||||
type mockIterator struct {
|
||||
keys [][]byte
|
||||
values [][]byte
|
||||
pos int
|
||||
}
|
||||
|
||||
func newMockIterator(keys [][]byte, values [][]byte) *mockIterator {
|
||||
return &mockIterator{
|
||||
keys: keys,
|
||||
values: values,
|
||||
pos: -1, // -1 means not initialized
|
||||
}
|
||||
}
|
||||
|
||||
func (m *mockIterator) SeekToFirst() {
|
||||
if len(m.keys) > 0 {
|
||||
m.pos = 0
|
||||
} else {
|
||||
m.pos = -1
|
||||
}
|
||||
}
|
||||
|
||||
func (m *mockIterator) SeekToLast() {
|
||||
if len(m.keys) > 0 {
|
||||
m.pos = len(m.keys) - 1
|
||||
} else {
|
||||
m.pos = -1
|
||||
}
|
||||
}
|
||||
|
||||
func (m *mockIterator) Seek(target []byte) bool {
|
||||
// Find the first key that is >= target
|
||||
for i, key := range m.keys {
|
||||
if bytes.Compare(key, target) >= 0 {
|
||||
m.pos = i
|
||||
return true
|
||||
}
|
||||
}
|
||||
m.pos = -1
|
||||
return false
|
||||
}
|
||||
|
||||
func (m *mockIterator) Next() bool {
|
||||
if m.pos >= 0 && m.pos < len(m.keys)-1 {
|
||||
m.pos++
|
||||
return true
|
||||
}
|
||||
if m.pos == -1 && len(m.keys) > 0 {
|
||||
m.pos = 0
|
||||
return true
|
||||
}
|
||||
return false
|
||||
}
|
||||
|
||||
func (m *mockIterator) Key() []byte {
|
||||
if m.pos >= 0 && m.pos < len(m.keys) {
|
||||
return m.keys[m.pos]
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
func (m *mockIterator) Value() []byte {
|
||||
if m.pos >= 0 && m.pos < len(m.values) {
|
||||
return m.values[m.pos]
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
func (m *mockIterator) Valid() bool {
|
||||
return m.pos >= 0 && m.pos < len(m.keys)
|
||||
}
|
||||
|
||||
func TestMergedIterator_SeekToFirst(t *testing.T) {
|
||||
// Create mock iterators
|
||||
iter1 := newMockIterator(
|
||||
[][]byte{[]byte("a"), []byte("c"), []byte("e")},
|
||||
[][]byte{[]byte("1"), []byte("3"), []byte("5")},
|
||||
)
|
||||
iter2 := newMockIterator(
|
||||
[][]byte{[]byte("b"), []byte("d"), []byte("f")},
|
||||
[][]byte{[]byte("2"), []byte("4"), []byte("6")},
|
||||
)
|
||||
|
||||
// Create a merged iterator
|
||||
merged := NewMergedIterator([]Iterator{iter1, iter2})
|
||||
|
||||
// Test SeekToFirst
|
||||
merged.SeekToFirst()
|
||||
if !merged.Valid() {
|
||||
t.Fatal("Expected iterator to be valid after SeekToFirst")
|
||||
}
|
||||
if string(merged.Key()) != "a" {
|
||||
t.Errorf("Expected first key to be 'a', got '%s'", string(merged.Key()))
|
||||
}
|
||||
if string(merged.Value()) != "1" {
|
||||
t.Errorf("Expected first value to be '1', got '%s'", string(merged.Value()))
|
||||
}
|
||||
}
|
||||
|
||||
func TestMergedIterator_Next(t *testing.T) {
|
||||
// Create mock iterators
|
||||
iter1 := newMockIterator(
|
||||
[][]byte{[]byte("a"), []byte("c"), []byte("e")},
|
||||
[][]byte{[]byte("1"), []byte("3"), []byte("5")},
|
||||
)
|
||||
iter2 := newMockIterator(
|
||||
[][]byte{[]byte("b"), []byte("d"), []byte("f")},
|
||||
[][]byte{[]byte("2"), []byte("4"), []byte("6")},
|
||||
)
|
||||
|
||||
// Create a merged iterator
|
||||
merged := NewMergedIterator([]Iterator{iter1, iter2})
|
||||
|
||||
// Expected keys and values after merging
|
||||
expectedKeys := []string{"a", "b", "c", "d", "e", "f"}
|
||||
expectedValues := []string{"1", "2", "3", "4", "5", "6"}
|
||||
|
||||
// Test sequential iteration
|
||||
merged.SeekToFirst()
|
||||
|
||||
for i, expected := range expectedKeys {
|
||||
if !merged.Valid() {
|
||||
t.Fatalf("Iterator became invalid at position %d", i)
|
||||
}
|
||||
if string(merged.Key()) != expected {
|
||||
t.Errorf("Expected key at position %d to be '%s', got '%s'",
|
||||
i, expected, string(merged.Key()))
|
||||
}
|
||||
if string(merged.Value()) != expectedValues[i] {
|
||||
t.Errorf("Expected value at position %d to be '%s', got '%s'",
|
||||
i, expectedValues[i], string(merged.Value()))
|
||||
}
|
||||
if i < len(expectedKeys)-1 && !merged.Next() {
|
||||
t.Fatalf("Next() returned false at position %d", i)
|
||||
}
|
||||
}
|
||||
|
||||
// Test iterating past the end
|
||||
if merged.Next() {
|
||||
t.Error("Expected Next() to return false after the last key")
|
||||
}
|
||||
}
|
||||
|
||||
func TestMergedIterator_Seek(t *testing.T) {
|
||||
// Create mock iterators
|
||||
iter1 := newMockIterator(
|
||||
[][]byte{[]byte("a"), []byte("c"), []byte("e")},
|
||||
[][]byte{[]byte("1"), []byte("3"), []byte("5")},
|
||||
)
|
||||
iter2 := newMockIterator(
|
||||
[][]byte{[]byte("b"), []byte("d"), []byte("f")},
|
||||
[][]byte{[]byte("2"), []byte("4"), []byte("6")},
|
||||
)
|
||||
|
||||
// Create a merged iterator
|
||||
merged := NewMergedIterator([]Iterator{iter1, iter2})
|
||||
|
||||
// Test seeking to a position
|
||||
if !merged.Seek([]byte("c")) {
|
||||
t.Fatal("Expected Seek('c') to return true")
|
||||
}
|
||||
if string(merged.Key()) != "c" {
|
||||
t.Errorf("Expected key after Seek('c') to be 'c', got '%s'", string(merged.Key()))
|
||||
}
|
||||
if string(merged.Value()) != "3" {
|
||||
t.Errorf("Expected value after Seek('c') to be '3', got '%s'", string(merged.Value()))
|
||||
}
|
||||
|
||||
// Test seeking to a position that doesn't exist but has a greater key
|
||||
if !merged.Seek([]byte("cd")) {
|
||||
t.Fatal("Expected Seek('cd') to return true")
|
||||
}
|
||||
if string(merged.Key()) != "d" {
|
||||
t.Errorf("Expected key after Seek('cd') to be 'd', got '%s'", string(merged.Key()))
|
||||
}
|
||||
|
||||
// Test seeking beyond the end
|
||||
if merged.Seek([]byte("z")) {
|
||||
t.Fatal("Expected Seek('z') to return false")
|
||||
}
|
||||
}
|
||||
|
||||
func TestMergedIterator_DuplicateKeys(t *testing.T) {
|
||||
// Create mock iterators with duplicate keys
|
||||
// In a real LSM tree, newer values (from earlier iterators) should take precedence
|
||||
iter1 := newMockIterator(
|
||||
[][]byte{[]byte("a"), []byte("c")},
|
||||
[][]byte{[]byte("newer_a"), []byte("newer_c")},
|
||||
)
|
||||
iter2 := newMockIterator(
|
||||
[][]byte{[]byte("a"), []byte("b")},
|
||||
[][]byte{[]byte("older_a"), []byte("b_value")},
|
||||
)
|
||||
|
||||
// Create a merged iterator
|
||||
merged := NewMergedIterator([]Iterator{iter1, iter2})
|
||||
|
||||
// Test that we get the newer value for key "a"
|
||||
merged.SeekToFirst()
|
||||
if string(merged.Key()) != "a" {
|
||||
t.Errorf("Expected first key to be 'a', got '%s'", string(merged.Key()))
|
||||
}
|
||||
if string(merged.Value()) != "newer_a" {
|
||||
t.Errorf("Expected first value to be 'newer_a', got '%s'", string(merged.Value()))
|
||||
}
|
||||
|
||||
// Next should move to "b", skipping the duplicate "a" from iter2
|
||||
merged.Next()
|
||||
if string(merged.Key()) != "b" {
|
||||
t.Errorf("Expected second key to be 'b', got '%s'", string(merged.Key()))
|
||||
}
|
||||
|
||||
// Then to "c"
|
||||
merged.Next()
|
||||
if string(merged.Key()) != "c" {
|
||||
t.Errorf("Expected third key to be 'c', got '%s'", string(merged.Key()))
|
||||
}
|
||||
}
|
||||
|
||||
func TestMergedIterator_SeekToLast(t *testing.T) {
|
||||
// Create mock iterators
|
||||
iter1 := newMockIterator(
|
||||
[][]byte{[]byte("a"), []byte("c"), []byte("e")},
|
||||
[][]byte{[]byte("1"), []byte("3"), []byte("5")},
|
||||
)
|
||||
iter2 := newMockIterator(
|
||||
[][]byte{[]byte("b"), []byte("d"), []byte("g")}, // g is the last key
|
||||
[][]byte{[]byte("2"), []byte("4"), []byte("7")},
|
||||
)
|
||||
|
||||
// Create a merged iterator
|
||||
merged := NewMergedIterator([]Iterator{iter1, iter2})
|
||||
|
||||
// Test SeekToLast
|
||||
merged.SeekToLast()
|
||||
if !merged.Valid() {
|
||||
t.Fatal("Expected iterator to be valid after SeekToLast")
|
||||
}
|
||||
if string(merged.Key()) != "g" {
|
||||
t.Errorf("Expected last key to be 'g', got '%s'", string(merged.Key()))
|
||||
}
|
||||
if string(merged.Value()) != "7" {
|
||||
t.Errorf("Expected last value to be '7', got '%s'", string(merged.Value()))
|
||||
}
|
||||
}
|
||||
Loading…
Reference in New Issue
Block a user