Most database requests only need to read data out of a database or write data into a database. However, client applications sometimes need to read and write data in a single interaction with the database.
Compound operations combine read and write operations in a single atomic statement, so there's no chance of data changing in between a read and a subsequent write; in fact, both operations take place in the same line of code from the perspective of your client application.
This property can be useful in cases where you want to write to a
specific document, but you haven't found it yet. If you just perform a
read for the document's
_id and then try to alter the document you
just found, it's possible that someone else can alter the document in
between your read and write operations. This doesn't stop you from doing
this work, but it can make error handling much more difficult. Compound
operations help keep your logic straightforward by handling that logic
entirely inside the database behind a layer of abstraction, so you don't
have to worry about it. While you can accomplish this task using
separate reads and writes, doing so requires the client application to
gracefully handle potential errors at any stage of the process and in
multiple potential error states. This increases the complexity of your
code and can make your client application brittle and difficult to test.
There are three major compound operations:
findOneAndDelete() matches multiple documents to a supplied query and removes the first of those matched documents.
findOneAndUpdate() matches multiple documents to a supplied query and updates the first of those matched documents using the provided update document.
findOneAndReplace() matches multiple documents to a supplied query and replaces the first of those matched documents using the provided replacement document.
All three methods accept an optional
options object with
configurable sort and
that work just like their read operation equivalents.
findOneAndDelete() allow the client to
returnDocument option, a boolean that determines if
the method returns the pre-update or post-update version of the modified