CODEWITHSUNDEEP
javafacebook-graph-api
Evans Y.
Evans Y.

Reputation: 4419

Facebook Graph API does response any data when limit is set to 20

I'm querying data in the Facebook Graph API explorer:

access_token="SECRET"
GET https://graph.facebook.com/me/home?limit=20&until=1334555920&fields=id

result:

{
  "data": [
  ]
}

I was shocked since there are many feeds on my "home".

Then I tried to set the limit to 100, then I got a feed list.

What's going on here? Does the "limit" parameter affect the graph api's result?

I tried to increase the limit to 25 and query again, there is one feed.

So what's the relationship between "limit" and "until"?

Upvotes: 3

Views: 1802

Answers (1)

PastryExplosion
PastryExplosion

Reputation: 703

Facebook's API can be a little weird sometimes because of the data you're trying to access and there's a few parts to this question.

Limits

The limits are applied when data is returned, but before permissions and access controls are generated, which is explained with this blog post from last year: Limits in the Graph API.

Permissions

More importantly, even if you give yourself a token with every FB permission possible, you still won't be able to access everything that you created. Say you post something on a Friend's feed, but their feed is not set to Public privacy. Any queries against that friend's feed with your token will never return data (Or at least that was the case around a year ago).

API Itself

One of the most awesome bugs I found in the Graph API when I was working with it last year is the way it handles paging. The Graph API allows three filters: limit, offset, and since/until. Somewhere Facebook recommends (and rightly so) that you make use of the since/until dates exclusively whenever possible for paging. Ignoring debates as to why you would do that vs. offsets on a theoretical basis, on a practical one the following query used to degrade over time:

// This obviously isn't valid as written, but you the params change as described
limit=fixed-value&offset=programmatic-increase&since=some-fixed-date-here

The reason: Date ranges and offsets don't behave well with each other. As an example, say I made the following initial query:

// My example query
limit=20&since=1334555920

--> {#1,#2, ... #20}

Naturally you would want to page more data. The result would be something like this (I can't remember the exact pattern, but the top n would be repeats and the list of results would be truncated by n/2 or something similar):

// My example query
limit=20&since=1334555920&offset=20

---> {#10, #11 ... #25}

I never figured out why it happened, but eventually the query would taper off to return nothing and you would only get around 50-100 unique values. If you paged using dates exclusively however, you could go on for as long as the data would let you.

This is with the caveat that this was a bug and this was from a while ago. The main lesson here is I never would have found this bug without modifying my query to make things that should come out exactly the same (A particular date range based on posts #10-30 compared with a limit=20, offset=10) but the results were quite different.

Upvotes: 3

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