Creating an index on a large embedded array in mongo

Question

I have a document with an embedded array. The array is just a bunch of strings. I recently came across some performance issues, so I decided to create an index. But it won't allow me to because the "key is too large to index".

I'm using AWS DocumentDB.

A sample doc looks like this:

{
  _id: (mongoID),
  id: (uuid),
  employees: [(uuid of another user), ...]
}

I saw the question Cannot create index in mongodb, "key too large to index" but I didn't really see how the solution applies to my question.

Does this answer your question? Cannot create index in mongodb, "key too large to index" — Valijon
– Valijon, Commented Feb 28, 2020 at 9:25
Which MongoDB version do you use? The limit should be removed in most recent version, see Index Key Limit — Wernfried Domscheit
– Wernfried Domscheit, Commented Feb 28, 2020 at 9:28
@WernfriedDomscheit I'm using AWS DocumentDB, as I wrote in the question. Also added a sample doc. — blockhead
– blockhead, Commented Feb 28, 2020 at 9:31
@Valijon I saw that answer but didn't see how it applied to my specific question. — blockhead
– blockhead, Commented Feb 28, 2020 at 9:32

Joseph Idziorek · Accepted Answer · 2020-04-25 13:18:59Z

1

We just updated this functionality, you can now create an index on arrays greater than 2048 bytes and create a compound multi-key index with multiple keys in the same array.

https://aws.amazon.com/about-aws/whats-new/2020/04/amazon-documentdb-adds-improved-multi-key-indexing-capabilities/

answered Apr 25, 2020 at 13:18

Joseph Idziorek

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Valijon · Accepted Answer · 2020-02-28 11:29:21Z

0

Array Indexing

Amazon DocumentDB indexes an array as a single entry. Arrays larger than 2048 bytes cannot currently be indexed.

https://docs.aws.amazon.com/documentdb/latest/developerguide/functional-differences.html#functional-differences.array-indexing

If employees has more than 56 entries, you cannot create index

answered Feb 28, 2020 at 11:29

Valijon

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1 Comment

Joseph Idziorek Over a year ago

Creating an index on an array larger than 2048 bytes has been added: aws.amazon.com/about-aws/whats-new/2020/04/…

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