MongoDB for Developers with Python Transcripts
Chapter: MongoDB's shell and native query syntax
Lecture: Updating documents in MongoDB
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0:01
If inserts are simple, updates maybe not so much.
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In fact, there are two types of updates that we're going to look at;
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first, we're going to look at what is the conceptually more simple one,
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but also slightly more problematic.
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So I'm going to call this the whole document update
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and the way you might use this is you might go to the database,
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do a query, get a document back, make a change to it
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and say here, push this whole document
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back over top the existing one in the database, kind of orm style.
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The other one that we're not talking about here would be the in place updates,
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so you might say go increment the view count of this post
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without retrieving it, without changing the other parts,
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ok, so how does the whole document update work?
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Well, first of all, we're going to do an update
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if we come back and we look at it, we'll see maybe we've changed the title here,
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the author is still the same, but we had to pass the author,
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we had to pass the published and the isbn back,
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okay, in fact also the id, so all that stuff we had to put back,
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basically the way it works is we're going to do a where clause here
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so find it by the primary key, this great long object id
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and then here is the entire whole document
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we want to replace that document with.
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Now because of the way it's working here,
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there's a couple of features or settings you might want to control here,
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so you might need to set these, you might not depending on what you're doing,
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the default is if the where clause does not match, nothing will happen,
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there will be no kind of upsert, there will not be a new document added
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because we didn't find one, just nothing happens.
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So if you say upsert is true and you run this update,
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it will say I didn't find this document, so let me create it for you,
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so you could control that here.
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Similarly with multi equal true, normally unlike sql statements
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update only updates the first item it finds
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even if the where clause would match ten things, it only updates one of them.
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So that's a little bit funky, but if you think it's entirely replacing the record
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like why would that hole record be duplicated ten times,
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I don't know, it's kind of weird, but if you do want to update multiple objects,
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multiple documents in this collection, be sure to set multi to true,
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both of those orange values, their default values are false.
