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Updating Data

Updating​

In order to update data, you can reference an existing subject by using its _id or, for any predicate marked as unique as a two-tuple, i.e. ["_user/username", "dsanchez"]. Predicates that you wish to update should be included as key-value pairs.

When referencing an existing subject, "_action": "update" is inferred. Note: When updating and upserting, you can use nested transactions.

Update using a two-tuple with a unique predicate. i.e. person/handle and relevant object:

[
  {
    "_id": ["person/handle", "dsanchez"],
    "age": 71
  }
]

Update using subject id:

[
  {
    "_id": 351843720888324,
    "age": 71
  }
]

Upserting​

You can upsert data if you have a unique predicate marked, "upsert": true. In this case, when a transaction with a tempid resolves to an existing subject, "_action": "upsert" is inferred.

We can make person/handle a upsertable predicate with the following

[
  {
    "_id": ["_predicate/name", "person/handle"],
    "upsert": true
  }
]

After issuing the above transaction, we can issue the below transaction, which will just update jdoe's age, rather than creating a new person.

[
  {
    "_id": "person",
    "handle": "jdoe",
    "age": 26
  }
]