How to limit an array size in MongoDB?

Question

is there a way I can limit the number of elements that can be added to a MongoDB Array? I have a Tables collection with an Attendees array that should only contain 10 elements seats).

Thank you!

kuzey beytar · Accepted Answer · 2022-06-21 11:45:26Z

35

You can use $slice as a modifier to $push when you update the document:

$push: { "field": { $each: ["val1", "val2"], $slice: -10 }}

This will cause field to only consist of the last 10 elements (giving you a "rolling window" of values pushed into the field).

edited Jun 21, 2022 at 11:45

kuzey beytar

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answered Apr 29, 2015 at 1:31

Chris Heald

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1 Comment

Steinfeld Over a year ago

For the full query: db.getCollection('col').updateOne({}, {$push: {"field": {$each: ["val1"], $slice: -10}}})

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