Update
This article provides an overview and how-to instructions for updating documents within Ditto.
There are two ways to modify documents in DQL:
UPDATE
When executing UPDATE to apply changes, only the minimum data necessary to enforce all peers converge on one view of the data sync across the mesh. (Updating)
INSERT
While INSERT operations modify all provided fields, even if they remain unchanged. (Inserting to Update)
Updating
To optimize performance and reduce unnecessary overhead, apply most updates in your app through the UPDATE method instead.
For the full DQL syntax, see *Ditto Query Language *> UPDATE.
Here is an example of a basic UPDATE operation on the cars collection:
Attachment Token
Once an ATTACHMENT object is created and linked to a document, it becomes immutable, meaning its contents cannot be changed.
However, you can indirectly update attachments by performing an UPDATE operation on the document to replace the existing attachment token with a different one. The attachment token is the reference pointer linking the document to the attachment’s binary data stored separately.
Before you can access an attachment in your app, you must actively fetch it, unlike a document, which is always readily accessible. For instructions, see READ.
MAP Data Type
To add a MAP to a document, use the operator syntax -> (...), allowing you to edit multiple child fields within a single MAP:
Multiple Documents
Modify multiple documents simultaneously based on a specified condition.
For example, here is a snippet demonstrating the UPDATE operation modifying all documents in the cars collection that are currently red, and changing their color to blue.
After the update, you can reference the documents modified by the mutatedDocumentIDs method on the result of the update.
Inserting with Update
The INSERT operation provides conflict policy options to override default behavior if a document with the same ID already exists.
For the full DQL syntax, see *Ditto Query Language *> INSERT.
By using the ON ID CONFLICT DO UPDATE policy, inserted documents automatically apply updates for all provided fields.
To optimize performance and reduce unnecessary overhead, apply most data modifications in your app through the UPDATE method.
MAP in a MAP
If you need to represent and organize highly complex data in a hierarchical structure, consider embedding a MAP within another MAP to establish a parent-child relationship within a document as follows: