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Now that we worked quite a bit on the different field operators, before we talk about array operators which

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are nice operators that help us with working and updating array values,

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let's dive into a nice option you can pass to update one and update many.

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First of all, let's quickly have a look at our persons again.

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These are the four documents we have, Max, Manuel, Anna and Chris

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and now let's say we want to update some document where we are not sure whether it exists in the collection

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or not

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beause you have an application where you don't know if the data was saved to the database yet and if

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it wasn't saved yet, you now want to create a new document,

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if it was, you want to override the existing or update the existing document and that is something you can

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do with db.users update one or many, works for both,

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let's say we're looking for name Maria and Maria does not exist here,

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important,

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we got Chris,

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we got Anna, we got Manuel, we got Max, we got no Maria here.

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So we're looking for the name Maria and I want to update this value.

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Now I will do that with $set

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and here let's say I'll set the age to 29,

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I'll set hobbies to one hobby to not type too much here, let's say title is good food, whoops, and the frequency

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is three times per week whatever

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and I also set isSporty to

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true, like that.

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Now if I hit enter, we found no magic document and hence no change was made.

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Now as I mentioned, maybe in such a scenario, we don't want to get this information and then manually insert

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that person but we want to let mongodb do that for us,

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either update or insert. And you can do that by passing a third argument to update one,

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so this is now not something you pass to your updating description but as a third argument to the

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update one method and there, there is a nice option you can set which is called upsert and you can set this

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to true,

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the default is false and you don't need to set the default of course. Now upsert

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simply is a combination of the word update and insert and means that if the document does not exist,

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it will be created.

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So now if I set this to true and I hit enter, you see it actually did not find anything, did not update

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anything but it upserted a document with this new ID.

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And if I now look into my objects, you see that this document was added

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and please note that it even set the name to Maria even though I did not add this in my update one

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operation, I filtered for this name

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but when I set values, I only set the age, the hobbies and isSporty. Now it automatically set a name

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because correctly mongodb assumed that for whatever you are filtering here, that this is something

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it should try to set, if it's an equality filter, it should try to set or it should set on the inserted

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document

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because if you looked for this, this should probably be part of the new document and that is why it also

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added name Maria here

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even though I only specified these three values or these three keys. So upsert can be very useful for

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working with updates where you don't know if something or if a certain document already exists.