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I am developing an application. In that application I had used the couchbase Lite for mobile. I did with syncing of all documents in the database from couchbase server. but the problem is that the database is large. I dont want to sync all documents from couchbase server. I want to sync only particular data/document from server.

My question is, how can I sync a particular document related to that particular user?

Eric Aya
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Sachin Nikumbh
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1 Answers1

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Document access for a particular user is done in the Sync Function. It's a function written in JavaScript that resides in the configuration file of Sync Gateway.

The methods available in the Sync Function are:

  • channel(channelname): Route a document to a channel.
  • access(username, channelname): Grant a username access to a channel (possibility to grant a role to a channel too, and as a result all users with that role get access to the channel).
  • role(username, rolename): Assign a user with a role.
  • requireAccess(channelname): Throws an error if the user in the context doesn't already have access to the channel.
  • requireUser(username): Throws an error if the user in the context isn't the username.
  • requireRole(rolename): Throws and error if the the user in the context doesn't have the role rolename.
  • throw({forbidden: "error message"}): Throw an exception for custom validation.

Here's an example of a config file with inline comments:

{
  "log": ["REST", "CRUD"],
  "users": {
    "foo1": {"password": "letmein", "admin_roles": ["admin"]},
    "foo2": {"password": "letmein"}
  },
  "databases": {
    "quizz": {
      "sync": `function(doc, oldDoc) {
        // The owner field shouldn't change during updates
        if (doc.owner != oldDoc.owner) {
          throw({forbidden: "Can't change the owner field on existing documents"});
        }
        switch(doc.type) {
          case "list":
            // only users with admin role can create/update list documents
            requireRole("admin");
            break;
          case "todo":
           // only the owner of a todo document can create/update it
           require(doc.owner);
           break;
        }
      }`
    }
  }
}

Note: The Sync Function should be pure which means that given an input (a document revision), the output should remain the same regardless of time (i.e. you can't make database/http requests for example). Also, it's not possible to modify the revision in the sync function.

See the docs on the Sync Function for more detail and this tutorial for a more in-depth example.

jamiltz
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