RDB Version History

RDB Version History

This document tracks the changes made to the dump file format over time.

An RDB file is forwards compatible. An older dump file format will always work with a newer version of Redis.

Version 7

Introduced 2014-01-08, integrated into Redis 2.9.x.

• New opcode: RESIZEDB (251). This encodes hash tables sizes to allow for faster loading.
  Followed by two length-encoded integers indicating:
  • Database hash table size
  • Expiry hash table size
• New opcode: AUX (250). This allows for arbitrary key-value settings. Unknown keys are ignored.
  Followed by two length-prefixed strings representing the key and value of the setting. Currently implemented fields:
  • redis-ver: The Redis Version that wrote the RDB
  • redis-bits: Bit architecture of the system that wrote the RDB, either 32 or 64
  • ctime: Creation time of the RDB
  • used-mem: Used memory of the instance that wrote the RDB
• New encoding type LIST_QUICKLIST (14)

Relevant links:

• opcode AUX: redis#206cd219, redis#4c0e8923
• opcode RESIZEDB: redis#e8614a1a
• new type LIST_QUICKLIST: redis#101b3a6e, Redis Quicklist: Do you even list?

Caution: This breaks backwards-compatibility. Redis 2.8 cannot load a RDB version 7 file.

Version 6

In previous versions, ziplists used a variable length encoding scheme for integers. Integers were stored in 16, 32 or 64 bits. In this version, this variable length encoding system has been extended.

The following additions have been made :

• Integers 0 through 12, both inclusive, are now encoded as part of the entry header
• Numbers between -128 and 127, both inclusive, are stored in 1 byte
• Numbers between -2^23 and 2^23 -1, both inclusive, are stored in 3 bytes

Issue ID: redis#469

To migrate to version 5:

• In redis.conf, set list-max-ziplist-entries to 0
• Restart Redis Server, and issue the SAVE command
• Edit the dump.rdb file, and change the rdb version in the header to REDIS0005

Version 5

This version introduced an 8 byte checksum (CRC64) at the end of the file. If checksum is disabled in redis.conf, the last 8 bytes will be zeroes.

Issue ID: redis#366

To migrate to version 4:

• Delete the last 8 bytes of the file (i.e. after the byte 0xFF)
• Change the rdb version in the header to REDIS0004

Version 4

This version introduced a new encoding for hashmaps - “Hashmaps encoded as Zip Lists”. This version also deprecates the Zipmap encoding that was used in previous versions.

“Hashmaps encoded as ziplists” has encoding type = 13. The value is parsed like a ziplist, and adjacent entries in the list are considered key=value pairs in the hashmap.

Issue ID: redis#285

To migrate to version 3:

• In redis.conf, set hash-max-ziplist-entries to 0
• Restart Redis Server, and issue the SAVE command
• Edit the dump.rdb file, and change the rdb version in the header to REDIS0003

Version 3

This version introduced key expiry with millisecond precision.

Earlier versions stored key expiry in the format 0xFD <4 byte timestamp>. In version 3, key expiry is stored as 0xFC <8 byte timestamp>. Here, 0xFD and 0xFC are the opcodes to indicate key expiry in seconds and milliseconds respectively.

Issue ID: redis#169

To migrate to version 2:

• If you don’t use key expiry, simply change the version in the header to REDIS0002
• If you use key expiry, you can still migrate, but there will be some loss in expiry precision. Also, the migration is a bit involved.
• For each key=value pair in the dump file, you will have to convert 0xFC <8 byte timestamp> to 0xFD <4 byte timestamp>.
• After converting the timestamps, change the version in the header to REDIS0002

Version 2

This version introduced special encoding for small hashmaps, lists and sets.

Specifically, it introduced the following encoding types:

REDIS_RDB_TYPE_HASH_ZIPMAP = 9
REDIS_RDB_TYPE_LIST_ZIPLIST = 10
REDIS_RDB_TYPE_SET_INTSET = 11
REDIS_RDB_TYPE_ZSET_ZIPLIST = 12

Commit: redis#6b52ad87

To migrate to version 1:

• In redis.conf, set the following properties to 0 hash-max-zipmap-entries, list-max-ziplist-entries, set-max-intset-entries, zset-max-ziplist-entries
• Restart Redis, and issue the SAVE command
• Edit the dump.rdb file, and change the rdb version in the header to REDIS0001