Compare two values in EventBridge rule and only trigger if they're different

Question

Hi there!

I'm trying to utilise EventBridge and are creating a rule. I get an event containing an oldState and a newState.
If a specific value has changed, I need to trigger the rule.

A good example could be the name of an item:

```json
{
  "detail": {
    "newState": {
      "name": "Potato"
    },
    "oldState": {
      "name": "Potat"
    }
}
```

I was thinking of using `anything-but` with the following path:

`$.detail.newState.name"

But that does not seem to work? Any suggestions as to how this should be handled?

E.g.:

```json
{
  "detail": {
    "newState": {
      "name": {
        "anything-but": {
          "prefix": "$.detail.oldState.name"
        }
      }
    },
    "oldState": {
      "name": [{"exists": true}]
    }
  }
}
```

Jesus Bernal · Answer

I believe what you are trying to achieve it's not possible. In EventBridge rules, you cannot directly compare two values within a single event to check if they're different. EventBridge rule patterns are designed for matching specific values, not for performing comparisons between fields.

As a workaround, you can perform the comparison on the producer and add a property to reflect if they are different (something like `hasChanged: true`, then the rule pattern evaluates this property) or perform the filter on the consumer. The former will avoid unnecesarry executions of the consumer.

Compare two values in EventBridge rule and only trigger if they're different

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