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Ok, so in the last lecture you got a brief overview over the different insert methods we have and how they work.

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I also briefly want to mention here that there are some other ways of inserting, one important alternative

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can be seen in the update module because there will have an option to either update a document or insert

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it if it doesn't exist yet

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but this is it from the insert method world for now.

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Now the more interesting part is now what you can do with these insert methods and there, you can actually

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define or specifies some additional information.

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Let's say we have our hobbies collection where we keep track of all the hobbies people could possibly

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have and we insert many hobbies here.

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Now each hobby is a document with the name of the hobby, like sports and we can have multiple such names,

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cooking and then here also cars,

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obviously it could hit enter now and it would work.

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Now I did mention that we get this auto-generated ID, right?

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Often you want to use that ID but it also is the case that you want to use your own ID,

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maybe because the data is fetched from some other database where you already had an ID or maybe because

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you need a shorter ID, here for example you could say the name of the sport also makes up for a great

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ID.

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So we could have _id sports here because we know that this will be unique,

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we will not have sports twice in this collection, so we can absolutely use sports as an ID here and the

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same here for cooking, we can of course also use cooking and I just name it all lowercase,

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you could absolutely use a capital C in there, that would be accepted,

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so this is not required to be lowercase but I'll use it like this

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and the same for my last document, for the cars,

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I'll set _id to cars. Now important,

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It has to be _id, just ID will not work,

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it has to be _id. If I now hit enter,

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you'll see these were the inserted IDs and indeed when we look into the database, we'll see no other IDs,

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so no object ID

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and this is perfectly fine and this is not bad to do,

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absolutely not, bring your own IDs if you have them,

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so now I got these three entries in there and I got my own ID.

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Now let's say I repeat that operation,

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so I add more hobbies, I add let's say yoga here

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and then let's leave the middle one untouched, I also add let's say hiking here. Now the middle one, cooking

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is untouched because let's say the process where we add this, maybe it's user added data doesn't guarantee

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that we check whether this item exists in the database before,

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so I try to enter data with an ID that already exists in the database.

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What happens if I now hit enter?

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Well if I do this, I get an error,

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now let's see what we got.

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I get an error, a write error at item 1, arrays start with index 0,

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so it tells us that the element at index 0, the first element succeeded but at index 1,

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so the second element in the array it failed. So we failed in that bulk operation and it gives us some

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more information,

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it tells us again where it failed and that it failed because of a duplicate key error collection.

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It could have also failed due to a different error, maybe our server went down during our operation,

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that could have been a thing,

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now here it failed due to duplicate key problems,

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it also tells us the ID, cooking,

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so it gives us the exact document on which it failed.

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So this is of course helpful but you also see here that one element was inserted

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and indeed if I find, whoops, if I reach out to my hobbies and I find them all and pretty print them, you see sports

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was added,

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cooking was added,

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cars was added,

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that was my first ride

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but in the last ride where I got the error, yoga which was the first document was added to the collection,

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so it failed after this element.

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Now this is the default behavior of mongodb

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and this is called an ordered insert and ordered inserts simply means that every element you insert

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is processed standalone

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but if one fails, it cancels the entire insert operation

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but it does not rollback the elements it already inserted,

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that's important but it cancels the operation and does not continue with the next document which as

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we know would have succeeded.

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So this is the default behavior, often

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you want that behavior, sometimes you don't

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and for these cases, you can override the behavior.

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Now if I repeat that same operation, it will again fail

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but now already on the first document because yoga was inserted in the last step, now it will of course

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fail because now it's already in the database.

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So how can I change this behavior?

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Well we can pass a second argument separated with a comma to insert many, that argument is a document

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and this is now not a document that will get inserted

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instead it is a document that configures this operation.

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And here we can set some options and the option that helps us in this case here is the ordered option,

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the ordered option allows us to specify whether mongodb should perform an ordered insert which is

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the default,

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you can set this to true but that is redundant because data is the default setting,

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so now it will behave in exactly the way we saw it before

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but we can also set this to false and now it will not be an ordered insert

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Now if I now hit enter, I still get that error

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but you'll see I now get a list of all the right errors,

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yoga and cooking which already tells us that it continued after failing on yoga

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and we also see that one element was inserted and that has to be hiking

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since we try to insert three and two of them failed. And indeed, if I now look into my database with find

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pretty, we see hiking in there.

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So by setting ordered to false here, we changed the default behavior and it is up to you what you require

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or what you want in your application.

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Be aware that it will never rollback the entire operation

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if something failed, that is something I'll cover towards the end of the course in the transactions

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module because we'll need some additional knowledge to work with such transactions.

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A rollback will not happen here but you can control whether it continues with the other documents and tries

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to insert everything which is fine or if it does not

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and being able to set this is very useful because you might have cases where you can't really control whether

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the data you are trying to insert already is in the database. And then an unordered insert with ordered

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false can be your solution because you don't care about any documents that fail,

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they already are in the database,

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that's fine for you

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and you can add everything which is not in there yet.

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So this is how you can use ordered and unordered inserts to finetune the way documents get inserted

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to your needs.