I get the below error message on a GraphQL query to Contentful, but do not understand why.
Error message:
"Query cannot be executed. The maximum allowed complexity for a query is 11000 but it was 12100. Simplify the query e.g. by setting lower limits for collections."
Query:
query ClassCollection(
$slug: String
$limit: Int
) {
classCollection(
where: { slug: $slug }
limit: $limit
) {
items {
slug
title
linkedFrom {
courseCollection {
items {
slug
}
}
}
filesCollection {
items {
title
asset {
title
fileName
url
width
height
contentType
}
}
}
}
}
}
Content model:
- Course
- A course contains a reference field pointing to one or more classes
- This is restricted to MAX 10 classes, in the content model
- Class
- A class contains a reference field pointing to one or more files
- This is restricted to MAX 10 files, in the content model
Notes
- Given the restrictions set in Contentful, the queries should not be very deep / complex.
- I only have a few entries in Contentful
Question
Why am I getting that error message and how can I fix it?
What I tried
- I can limit the number of query results, but that is not solving the underlying problem. In any case, the query becomes too complex already at a limit of 50 or so. Which is way too little.
- Since I am trying to figure out what course each class comes from, I could just pull all the courses and all the classes (which is not too complex), and then do a quick array filter in JavaScript based on slugs. However, it would be much nicer to do it directly in the query. Here is a link showing Contentful recommending the linkedFrom field for this purpose.
EDIT: Calculating the Query Complexity
- For the sake of the calculation, let's assume we limit the number of classes, via the query, to 100. So, 100 classes maximum.
- Then, since each course can contain a maximum of 10 classes, the maximum number of courses that could be returned is 1,000. I am not sure about this one actually. It has to look at each course, and find the class, which should be 1,000 lookups max.
- Each class can only have 10 files at most, giving us a complexity of 1,000 here as well.
- That is a maximum complexity of 2,100. I am obviously wrong, since the error message says the complexity is 12,100. Any idea what I am missing?
EDIT 2
- I checked the x-contentful-graphql-query-cost header in DevTools, and the cost without requesting the filesCollection is 10,100.
- With the filesCollection, but without the linkedFrom field, it is 2,100.
- Thus, the problem is clearly with the linkedFrom field.
- I am currently thinking that since classes return up to 100 entries, and since the default number of entries in Contentful is 100, the reverse look-up that linkedFrom probably has to do, checks 100 class entries for each of the 100 courses. Thus ending up at 100 * 100 = 10,000 complexity.
Conclusion
- Unless someone has a better idea, I will conclude that it is in fact better to do the connecting of classes to courses in JavaScript, after the data has been pulled. That way we only work on a limited set, not the worst case scenario of 100 * 100.
