dgraph-io/badger · critical

invalid index length in footer. Data corrupted

Error message

invalid index length in footer. Data corrupted

What it means

The index length read from the footer must be positive and must fit within the bytes remaining between the footer and the start of the file. Zero is always invalid (every table has at least one block, hence a non-empty index); too-large values indicate corruption.

Source

Thrown at table/table.go:463

	// Read checksum.
	expectedChk := &pb.Checksum{}
	readPos -= checksumLen
	buf = t.readNoFail(readPos, checksumLen)
	if err := proto.Unmarshal(buf, expectedChk); err != nil {
		return nil, err
	}

	// Read index size from the footer.
	if readPos < 4 {
		return nil, errors.New("invalid table size in footer. Data corrupted")
	}
	readPos -= 4
	buf = t.readNoFail(readPos, 4)
	t.indexLen = int(y.BytesToU32(buf))
	// A table always has at least one block, so a zero indexLen is always
	// corruption, and the index must fit in the bytes remaining before readPos.
	if t.indexLen <= 0 || t.indexLen > readPos {
		return nil, errors.New("invalid index length in footer. Data corrupted")
	}

	// Read index.
	readPos -= t.indexLen
	t.indexStart = readPos
	data := t.readNoFail(readPos, t.indexLen)

	if err := y.VerifyChecksum(data, expectedChk); err != nil {
		return nil, y.Wrapf(err, "failed to verify checksum for table: %s", t.Filename())
	}

	index, err := t.readTableIndex()
	if err != nil {
		return nil, err
	}
	if !t.shouldDecrypt() {
		// If there's no encryption, this points to the mmap'ed buffer.
		t._index = index

View on GitHub (pinned to 2a001d466f)

Solutions

1. Quarantine the offending SST file and let Badger continue with remaining tables
2. Restore the file from a verified backup and compare checksums
3. Confirm all files were produced by the same Badger major version
4. If corruption is widespread, restore the whole directory or rebuild via db.Load

Example fix

// before: retrying db.Open on the same corrupt dir

// after: move corrupt table aside, reopen
tableSize, _ := t.Size()
_ = tableSize
os.Rename("data/000012.sst", "data/000012.sst.corrupt")
db, err := badger.Open(opt)

// inspect footer indexLen yourself before trusting the dir
idxLen := binary.LittleEndian.Uint32(tail[8:12])
if idxLen == 0 || int(idxLen) > len(data)-12 {
    os.Rename(tablePath, tablePath+".corrupt") // let DB open without it
}

When it happens

Trigger: Opening a table whose footer's indexLen field is zero, negative (uint32 overflow), or exceeds the remaining readable bytes — corrupted footer, garbage tail bytes, or cross-version format mismatch.

Common situations: Tail-overwritten SSTs after disk issues; files copied from an incompatible format; interrupted writes producing zero-filled footer regions.

Related errors

• invalid table size in footer. Data corrupted
• invalid checksum length in footer. Data corrupted
• initIndex crashed: %v %s
• failed to read block offset from index. Data corrupted
• block out of index

AI-assisted analysis of dgraph-io/badger@2a001d466f (2026-09-05). Data as JSON: /api/errors/7c4a0f43be9ba003. Report an issue: GitHub.