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I have a mobile app using Couchbase lite. When the user logouts, I want to remove some of the documents on the device; the user-specific documents. I do not want to remove all of the documents. Documents have a purgeDocument() method that I thought I could call on those user-specific documents.

The problem is that the purged documents are not re-synced down to the device if the user logs back in and a pull replication is run.

Based on the little I know of CouchDB sync protocol, it makes sense that those are not re-synced down because there are not newer Sequence updates on those user-specific documents to trigger a re-sync.

How should I approach this problem?

Possibilities

  1. Delete the whole database (including common documents) and lose performance.
  2. Somehow reset the last sequence for the replicator and hope the replicator does not transfer the already-downloaded docs over the wire. (Probably would screw up CBL)
  3. Have separate databases, one that stores the user-specific docs and one that contains common docs. Databases can have filtered replicators (by channel) so it would be feasible to partition the incoming data into separate databases. The problem would be the seamless reference loading between documents of differing databases when using CBLModel objects wrappers.
Joel Jeske
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4 Answers4

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As i understand from the official documentation in the subsection Purging documents, you are not retrieving the document again just because it has not been modified/updated (in short, its rev is the same) on the server side.

You can try to create again a dummy document with the same type and, for example, username (or whatever you are using to identify the user's configuration) when the user logs again in your app so that you trigger the pull replication from the server. You probably will have a conflict that can easily be solved taking the revision from the server.

I hope this idea helps a little.

UPDATE AFTER COMMENT

The idea is to store somewhere the id and type of the user's documents you're going to purge. That way you can create a new dummy document with those two fields when the user logs in again. Perhaps this new dummy document triggers the pull replication.

NOTE: I haven't tried this method. I am just guessing what it might be a work around to your problem.

kazbeel
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  • So you are suggesting that upon login, I create a duplicate user record that I know exists on the server but is missing on the device, and then the server will send down the correct document? I don't understand why the server would push down the conflicting revision. – Joel Jeske Dec 22 '15 at 17:05
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I would suggest that your backend modifies the selected documents - this could be just a timestamp update - upon user login, which will post the new revisions to the device

Leonid Usov
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You can keep purging the documents when the user logs in.

To solve problem of re-syncing specific document, I think the easiest way is to use filtered replication where the filter is document id.

These document IDs can be created in a manner which can be derived. For example it can be as UserDocument::.

Now when the user logs in you can start one shot replication with document ID as filter. This can only be done in one shot. And when this One Shot finishes you can start replication again by changing the setting of the replication(changing filter/channel).

following is the URL by Couchbase which explains filtered replication by document ID.

https://developer.couchbase.com/documentation/mobile/1.4/guides/couchbase-lite/native-api/replication/index.html#filtering-by-document-ids

Pankaj Sharma
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Try Push after Purging the document with Couchbase Lite which allows you to Pull the document from the server at a later point.

Ranjeesh
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