How to push an array element only if it is a insert

Question

I want to add an element to the array and add new field to the database if result of the query is an insert. If it is not an insert(if it is a update) I don't want to update the array and add new field.

To add new field on insert; I use $setOnInsert.

To add element to the array I use, $addToSet: { "children": {"age": 12}},

I tried but it seems that it is not possible to use $addToSet inside $setOnInsert. So how can add an array element if it is an insert?

JohnnyHK · Accepted Answer · 2016-04-12 12:45:44Z

3

Because the doc is being created in the insert case, you would just create the initial children array with that element:

{$setOnInsert: {children: [{age: 12}]}}

answered Apr 12, 2016 at 12:45

JohnnyHK

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4 Comments

Yigit Can Over a year ago

But, array of children already has some elements? Actually, that was why I use $addToSet or $push. This way, children array will be erased, am I wrong?

JohnnyHK Over a year ago

$setOnInsert is only used in the insert case where the document doesn't exist, so there can't already be children array elements.

JohnnyHK Over a year ago

@YigitCan If I'm misunderstanding your question, can you add details to your post about the specific case this won't work for?

Yigit Can Over a year ago

You're right about children elements, the answer works, thank you so much.

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