Function Open

db.go:194–418

Open returns a new DB object.

(opt Options)

// Open returns a new DB object.
func Open(opt Options) (db *DB, err error) {
	if opt.InMemory && (opt.Dir != "" || opt.ValueDir != "") {
		return nil, errors.New("Cannot use badger in Disk-less mode with Dir or ValueDir set")
	}
	opt.maxBatchSize = (15 * opt.MaxTableSize) / 100
	opt.maxBatchCount = opt.maxBatchSize / int64(skl.MaxNodeSize)

	// We are limiting opt.ValueThreshold to maxValueThreshold for now.
	if opt.ValueThreshold > maxValueThreshold {
		return nil, errors.Errorf("Invalid ValueThreshold, must be less or equal to %d",
			maxValueThreshold)
	}

	// If ValueThreshold is greater than opt.maxBatchSize, we won't be able to push any data using
	// the transaction APIs. Transaction batches entries into batches of size opt.maxBatchSize.
	if int64(opt.ValueThreshold) > opt.maxBatchSize {
		return nil, errors.Errorf("Valuethreshold greater than max batch size of %d. Either "+
			"reduce opt.ValueThreshold or increase opt.MaxTableSize.", opt.maxBatchSize)
	}
	if !(opt.ValueLogFileSize <= 2<<30 && opt.ValueLogFileSize >= 1<<20) {
		return nil, ErrValueLogSize
	}
	if !(opt.ValueLogLoadingMode == options.FileIO ||
		opt.ValueLogLoadingMode == options.MemoryMap) {
		return nil, ErrInvalidLoadingMode
	}

	// Return error if badger is built without cgo and compression is set to ZSTD.
	if opt.Compression == options.ZSTD && !y.CgoEnabled {
		return nil, y.ErrZstdCgo
	}
	// Keep L0 in memory if either KeepL0InMemory is set or if InMemory is set.
	opt.KeepL0InMemory = opt.KeepL0InMemory || opt.InMemory

	// Compact L0 on close if either it is set or if KeepL0InMemory is set. When
	// keepL0InMemory is set we need to compact L0 on close otherwise we might lose data.
	opt.CompactL0OnClose = opt.CompactL0OnClose || opt.KeepL0InMemory

	if opt.ReadOnly {
		// Can't truncate if the DB is read only.
		opt.Truncate = false
		// Do not perform compaction in read only mode.
		opt.CompactL0OnClose = false
	}
	var dirLockGuard, valueDirLockGuard *directoryLockGuard

	// Create directories and acquire lock on it only if badger is not running in InMemory mode.
	// We don't have any directories/files in InMemory mode so we don't need to acquire
	// any locks on them.
	if !opt.InMemory {
		if err := createDirs(opt); err != nil {
			return nil, err
		}
		if !opt.BypassLockGuard {
			dirLockGuard, err = acquireDirectoryLock(opt.Dir, lockFile, opt.ReadOnly)
			if err != nil {
				return nil, err
			}