Update if entity has changed - feedback request

Users
1

I’m a clojure and xtdb n00b, but I’ve come up with this functionality, and I’d like some feedback.

Is this a reasonable way to update the record only if it’s changed? Some documents may be over 1Mb in size.

It’s working thus far, but I want to make sure I’m not setting myself for failure down the road.

POST /_xtdb/submit-tx

{
  "tx-ops": [
    [
      "put",
      {
        "xt/id": "hash",
        "xt/fn": "(fn [m] (hash (into (sorted-map) m)))"
      }
    ]
    [
      "put",
      {
        "xt/id": "update-if-different",
        "xt/fn":"
          (fn [ctx new-entity]
            (if (not= (hash new-entity)
                      (hash (xtdb.api/entity
                              (xtdb.api/db ctx)
                              (get new-entity :xt/id))))
              [[:xtdb.api/put new-entity]]
            )
        )"
      }
    ]
  ]
}

POST /_xtdb/submit-tx

{
  "tx-ops": [
    [ "fn" => "update-if-different", { "xt/id" => "555555", name => "bruh"}]
  ]
}
2

Hey @tempire apologies for the delayed response. In general XTDB v1 will deduplicate when documents are exactly the same - you shouldn’t need to attempt to detect or avoid this. Write amplification may only become a problem if your 1MB documents change by a couple of bytes each time, as each version is then stored under a distinct internal hash.

I think your approach shown shouldn’t interfere with the native mechanism though, so hopefully you are already observing the behaviour you are looking for :slight_smile: (though there is a slight processing cost to using a transaction function each time for this)