Redis [NEW] Add a new command RESTORECOMPARE to diff two key value.

The problem/use-case that the feature addresses

A description of the problem that the feature will solve, or the use-case with which the feature will be used.

use-case see issue Check migrated data consistency

User want to check data consistency after migration. so we could provide a command RESTORECOMPARE

RESTORECOMPARE key ttl serialized-value [ABSTTL]

To implement this command. pseudocode like following

int restoreCompare(key, ttl, serialized-value) {
    // for example handle map comparison
    map source = redis.get(key)

    // deserialize dump value and store to temporary structure
    map temp = deserialize(serialized-value)

    // comparison process
    if (source == nil) {
        return 0
    }
    if (source equals temp) {
        return 1
    } else {
        return 0
    }

    // if type is module. 
    // first compare module-name and module-version
    // after above compare serialized-value directly.
}

After implement above command. redis-cli can add a diff option too. redis-cli --diff dump.rdb -h 127.0.0.1 -p 6379

step1: convert dump.rdb to redis dump format. step2: use RESTORECOMPARE to do diff process.

see also Fast and Efficient Parallelized Comparison of Redis Databases

Comment From: yangbodong22011

@leonchen83 Is there a new solution to your problem? For example, by dump key and comparing it locally.

Comment From: leonchen83

different rdb version has different RDB_TYPE for example: map may stored by following type

RDB_TYPE_HASH = 4;
RDB_TYPE_HASH_ZIPMAP = 9;
RDB_TYPE_HASH_ZIPLIST = 13;
RDB_TYPE_HASH_LISTPACK = 16;

so we need to compare every field in map type, compare dump directly can't solve problem

Comment From: yangbodong22011

different rdb version has different RDB_TYPE for example: map may stored by following type

RDB_TYPE_HASH = 4; RDB_TYPE_HASH_ZIPMAP = 9; RDB_TYPE_HASH_ZIPLIST = 13; RDB_TYPE_HASH_LISTPACK = 16;

so we need to compare every field in map type, so compare dump can't solve problem

oh, i see, but it seems RESTORECOMPARE command is less necessary than comparing field/values by the client itself.

Comment From: leonchen83

yes, above can compare in client side, but server side provide this command can simplify compare process. RedisFullCheck and redis-rdb-cli can benefit from this command

Comment From: itamarhaber

@leonchen83 I didn't know/forgot about RedisFullCheck & RedisShake - cool :)