What causes "Unsupported compression type" in dgraph-io/badger?

Set Options.Compression to options.None, options.Snappy, or options.ZSTD before opening/creating the DB

Unsupported compression type

Error message

Unsupported compression type

What it means

Builder.compressData encodes a block according to the table's compression option. Only None (no compression), Snappy (s2), and ZSTD are implemented; any other options.Compression value causes compressData to return the 'Unsupported compression type' error, which fails the table build.

Source

Thrown at table/builder.go:523

func (b *Builder) shouldEncrypt() bool {
	return b.opts.DataKey != nil
}

// compressData compresses the given data.
func (b *Builder) compressData(data []byte) ([]byte, error) {
	switch b.opts.Compression {
	case options.None:
		return data, nil
	case options.Snappy:
		sz := s2.MaxEncodedLen(len(data))
		dst := b.alloc.Allocate(sz)
		return s2.EncodeSnappy(dst, data), nil
	case options.ZSTD:
		sz := y.ZSTDCompressBound(len(data))
		dst := b.alloc.Allocate(sz)
		return y.ZSTDCompress(dst, data, b.opts.ZSTDCompressionLevel)
	}
	return nil, errors.New("Unsupported compression type")
}

func (b *Builder) buildIndex(bloom []byte) ([]byte, uint32) {
	builder := fbs.NewBuilder(3 << 20)

	boList, dataSize := b.writeBlockOffsets(builder)
	// Write block offset vector the the idxBuilder.
	fb.TableIndexStartOffsetsVector(builder, len(boList))

	// Write individual block offsets in reverse order to work around how Flatbuffers expects it.
	for i := len(boList) - 1; i >= 0; i-- {
		builder.PrependUOffsetT(boList[i])
	}
	boEnd := builder.EndVector(len(boList))

	var bfoff fbs.UOffsetT
	// Write the bloom filter.
	if len(bloom) > 0 {

View on GitHub (pinned to 2a001d466f)

Solutions

Set Options.Compression to options.None, options.Snappy, or options.ZSTD before opening/creating the DB
If options were persisted, delete or fix the option/manifest so a supported compression id is loaded
Check the options package of your Badger version for the exact enum constants; don't cast raw ints into options.Compression
If high compression isn't required, fall back to options.None to guarantee compatibility

Example fix

// before
opts := badger.DefaultOptions(dir)
opts.Compression = options.Compression(7) // unknown type
// after
opts := badger.DefaultOptions(dir)
opts.Compression = options.ZSTD // or options.Snappy / options.None

Defensive patterns

Strategy: validation

Validate before calling

func compressionSupported(c options.Compression) bool {
	return c == options.None || c == options.Snappy || c == options.ZSTD
}
if !compressionSupported(opts.Compression) {
	return errors.New("unsupported compression type in options")
}

Type guard

func isKnownCompression(c options.Compression) bool {
	switch c {
	case options.None, options.Snappy, options.ZSTD:
		return true
	default:
		return false
	}
}

Try / catch

data, err := b.compressData(dst, block, blockOff)
if err != nil {
	if strings.Contains(err.Error(), "Unsupported compression type") {
		// fall back to a supported compression
		return b.compressData(dst, block, blockOff) // after correcting opts.Compression
	}
	return err
}

Prevention

Only assign options.Compression from its enum constants, never raw ints
Keep badger versions consistent between the process that writes options and the one that reads them
Default to options.Snappy or options.ZSTD from DefaultOptions rather than custom values
Check the options enum in your vendored version before enabling compression

When it happens

Trigger: Creating a table (via builder handleBlock) with opts.Compression set to a value other than options.None, options.Snappy, or options.ZSTD — e.g. a value from a different/older options enum, a custom integer cast, or an options file that persisted an unknown compression id.

Common situations: Migrating options across Badger versions where the compression enum changed; constructing Options programmatically with an invalid compression constant; restoring a DB whose option metadata references an algorithm this build doesn't support (e.g. a build without ZSTD support in older versions).

Related errors

AI-assisted analysis of dgraph-io/badger@2a001d466f (2026-09-05). Data as JSON: /api/errors/935cc1b79a0305af. Report an issue: GitHub.