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Comparing arrays in GROQ query to find intersections.

4 replies
Last updated: Feb 28, 2024
Can someone help me with line 5 - I'm trying to compare two arrays, one is the field allCheckinIds (an array of strings) and the other is a variable $userIds (also an array of strings). I'm trying to see whether there are at least one "intersection" between them.
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For checking if two arrays have at least one intersection (overlapping value), you can use the count() function combined with the @ filter operator in GROQ. Here's the pattern:

count(array1[@ in array2]) > 0

So if you have a field allCheckinIds and a parameter $userIds, you'd write:

count(allCheckinIds[@ in $userIds]) > 0

This works by:

  1. Taking the first array (allCheckinIds)
  2. Filtering it with [@ in $userIds] - the @ represents each element in the array, and checks if it exists in the second array
  3. Counting how many matches were found
  4. Checking if that count is greater than 0

You can use this in a filter to find documents that have at least one matching value:

*[_type == "yourType" && count(allCheckinIds[@ in $userIds]) > 0]

This is a clever workaround since GROQ doesn't have a built-in array intersection operator. The technique comes from this community discussion where the same question was asked.

If you need to pass userIds as a parameter (which is common when querying from your application), you'd use it like this with the JS client:

client.fetch(
  `*[_type == "yourType" && count(allCheckinIds[@ in $userIds]) > 0]`,
  { userIds: ['id1', 'id2', 'id3'] }
)
function checkIntersection(array1, array2) {
    return array1.some(item => array2.includes(item));
}
Not sure if you mean something like this
Correct, but I would like to do it in the GROQ-query itself.
Comparing two arrays will require syntax like seen here , which uses the 
count()
function and the parent operator. Presumably, it’ll be something like:

checkinId in $userIds ||
count((allCheckinIds[])[@ in $userIds]) > 0
Great, thank you so much!

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