Introduction
The Twitter API has several methods, such as GET statuses / user_timeline and GET statuses / home_timeline, which return a timeline of Tweet data. Such timelines can grow very large, so there are limits to how much of a timeline a client application may fetch in a single request. Applications must therefore iterate through timeline results in order to build a more complete list.
Because of Twitter’s realtime nature and the volume of data which is constantly being added to timelines, standard paging approaches are not always effective. The goal of this page is to demonstrate the issues Twitter developers may face when paging through result sets and to give best practices for processing a timeline.
The problem with “pages”
In an ideal world, paging would be very easy to implement. Consider the case where a timeline has 10 reverse-chronologically sorted Tweets. An application might attempt to read the entire timeline in two requests by setting a page size of 5 elements and requesting the first page, then the second page. The following image demonstrates this approach:
The problem with this method is that Twitter timelines are constantly having new Tweets added to their front. Consider the previous example. If two new Tweets are added to the timeline between the first and second calls, the second fetch retrieves two Tweets which were returned in the previous call:
In fact, if 5 or more Tweets were added between calls, subsequent calls would eventually retrieve all the Tweets returned from the first request - making an entire API request completely redundant.
The max_id parameter
The solution to the issue described above is to use a technique for working with streams of data called cursoring. Instead of reading a timeline relative to the top of the list (which changes frequently), an application should read the timeline relative to the IDs of Tweets it has already processed. This is achieved through the use of the max_id request parameter.
To use max_id correctly, an application’s first request to a timeline endpoint should only specify a count. When processing this and subsequent responses, keep track of the lowest ID received. This ID should be passed as the value of the max_id parameter for the next request, which will only return Tweets with IDs lower than or equal to the value of the max_id parameter. Note that since the max_id parameter is inclusive, the Tweet with the matching ID will actually be returned again, as shown in the following image:
Optimizing max_id for environments with 64-bit integers
While one redundant Tweet is not terribly inefficient, it is still possible to optimize max_id requests to address this problem if your platform is capable of working with 64-bit integers. Environments where a Tweet ID cannot be represented as an integer with 64 bits of precision (such as JavaScript) should skip this step. Subtract 1 from the lowest Tweet ID returned from the previous request and use this for the value of max_id. It does not matter if this adjusted max_id is a valid Tweet ID, or if it corresponds with a Tweet posted by a different user - the value is just used to decide which Tweets to filter. When adjusted in this manner, it is possible to page through a timeline without receiving redundant Tweets:
Using since_id for the greatest efficiency
Applications which process a timeline, wait some quantity of time, and then need to process new Tweets which have been added since the last time the timeline was processed can make one more optimization using the since_id parameter.
Consider the previous example where Tweets 1 through 10 were processed. Now imagine that Tweets 11 through 18 were added to the timeline since the processing in the previous example began. An inefficient approach to process the new Tweets would be to iterate from the start of the list until Tweet 10 appeared. As shown in the following image, this causes two Tweets which have already been processed to be returned again:
This problem is avoided by setting the since_id parameter to the greatest ID of all the Tweets your application has already processed. Unlike max_id the since_id parameter is not inclusive, so it is not necessary to adjust the ID in any way. As shown in the following image, Twitter will only return Tweets with IDs higher than the value passed for since_id.
Applications which use both the max_id and since_id parameters correctly minimize the amount of redundant data they fetch and process, while retaining the ability to iterate over the entire available contents of a timeline.