Conditional Upsert in Couchbase - couchbase

Question

I have documents that would look like this:
{
"name": "n",
"age": 22
//other properties
"hash": "XyRZHDJJD6738..." //This property contains the hash of the object (calculated by the client)
}
From the client, I should whether:
Update the document using its key (known), ONLY if the hash is different (=> The stored object and the new object are not the same)
Insert the document if the Key doesn't exist
This operation is done in a bulk mode on a relatively large dataset, with concurrent access => So fetching the document then updating is not an option.
Is there a way to do this in Couchbase (5.1+)?

Answer 1

With a tweak to the document model, you could have something like this:
{
"name": "n",
"age": 22,
"applied_hashes": {
"XyRZHDJJD6738": null,
"AB2343DCxdsAd": null,
// ... other hashes
}
}
Now you can do each update as a Sub-Document operation, with the first spec being to try and insert the hash of the update into applied_hashes. If that hash/update has previously been applied, then this insert will fail, and as Sub-Document is atomic no changes will be made to the document.
With Java SDK 3.x this looks like:
try {
collection.mutateIn("id",
Arrays.asList(
MutateInSpec.insert("applied_hashes.XyRZHDJJD6738", null).createPath(),
MutateInSpec.upsert("age", 24)
// .. other parts of update XyRZHDJJD6738 here
));
}
catch (PathExistsException err) {
// Update XyRZHDJJD6738 has already been applied
// No changes have been made to the document
}