Chapter 6. Updates, atomic operations, and deletes
In this chapter
- Updating documents
- Processing documents atomically
- Category hierarchies and inventory management
To update is to write to existing documents. But to do this effectively requires a thorough understanding of the kinds of document structures available and of the query expressions made possible by MongoDB. Having studied the e-commerce data model throughout the last two chapters, you should have a good sense for the ways in which schemas are designed and queried. We’ll use all of this knowledge in our study of updates.
Specifically, we’ll look more closely at why we model the category hierarchy in such a denormalized way, and how MongoDB’s updates make that structure reasonable. We’ll explore inventory management and solve a few tricky concurrency issues in the process. You’ll get to know a host of new update operators, learn some tricks that take advantage of the atomicity of update operations, and experience the power of the findAndModify command. After numerous examples, there will be a section devoted to the nuts and bolts of each update operator. I’ll also include some notes on concurrency and optimization, and then end with a brief but important summary of how to delete data in MongoDB.
By the end of the chapter, you’ll have been exposed to the full range of MongoDB’s CRUD operations, and you’ll be well on your way to designing applications that best take advantage of MongoDB’s interface and data model.