Use JavaScript within FQL

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,
1

Hello!

Apologies if this is already documented/answered somewhere. Feel free to point me to that if that’s true. I tried to use by basic search skills, but that did not yield any useful results.

Coming to the actual question, my use case is that, I wish to pull data from an API. The API mentions, try not to poll it more than once per 3 days as it won’t update as frequently, and we would be burderning its servers. So, I thought of saving the data in Fauna.

I’m using Netlify Functions (TypeScript) with a Vue frontend, so saving the data in a file is not an option as I’d have to re-deploy the entire site to update the data.

Here’s what I’m planning to do:

Retrieve the document from Fauna → Compare its ts with Now() → If it’s greater than 3 days, pull the data from API and update the document → If not, simply use the data from Fauna.

I constructed a basic Query:

Let({
  doc: Get(
    Ref(
      Collection(
        'foo'
      ),
      'bar'
    )
  )}, GTE(
    TimeDiff(
      Epoch(
        Select(
          'ts',
          Var('doc')
        ),
        'microseconds',
      ),
      Now(),
      'days'
    ),
    3
  )
)

I stored the document as a variable doc, because I assumed, I can update the same ref later in the query. My previous query involved me directly using Get() inside Select(), thus, avoiding Let() altogether.

Now my question is, I can use If() to check the condition as mentioned above. What I don’t know is, if I can use plain JavaScript code (using fetch or axios) to pull data from API and update the document in the same query. I can achieve this using standard JavaScript code, like:

db.query(
  GTE(
    TimeDiff(
      Epoch(
        Select(
          'ts',
          Get(
            Ref(
              Collection(
                'foo'
              ),
              'bar'
            )
          )
        ),
        'microseconds',
      ),
      Now(),
      'days'
    ),
    3
  )
).then(response => {
  if (response) {
    // greater than 3 days, need to update
    // also query Fauna again to store the updated data
  } else {
    // less than 3 days, can use that data,
    // but now, I'll have to query Fauna again to fetch the document data
  }
})

Note, my above code might have syntax errors in the FQL, because I’ve hand-typed it without checking perfectly for bracket closures. I’m just trying to represent what I’m trying to achieve.

2

Hi @hrishikesh! No, you cannot execute external requests within a request to Fauna. You will have to use Javascript to make a second request after you make the external request yourself.

In your example, you reference the document directly with Ref(Collection("foo"), "bar"). In that case you can use the same Ref in your second request.

If your real code doesn’t have the exact Ref, for example if you are using an Index, then you could return a tuple (array) of the Ref and your calculated result.

Let(
  {
    ref: Ref(Collection("foo"), "bar"), // or Match(Index("foo_by_unique_field"))
    doc: Get(Var("ref")),
    is_old: GTE(
      TimeDiff(
        Epoch(Select('ts', Var('doc')), 'microseconds'),
        Now(),
        'days'
      ),
      3
    )
  },
  [Var("ref"), Var("is_old")] 
)
3

Thanks for the answer. That’s what I imagined would be the case, but just wanted to confirm!

4

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