[GitHub] [couchdb] priyath opened a new issue #2045: Stale couch view after purging document with conflicted revision tree

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priyath opened a new issue #2045: Stale couch view after purging document with conflicted revision tree
URL: https://github.com/apache/couchdb/issues/2045
 
 
   A couple of days back, I raised a question regarding a sporadic issue we observed related to Couch views returning stale data. (Reference: https://github.com/apache/couchdb/issues/2040)
   
   I have found out the reason for this and would like some insight from the community to understand this problem better.
   
   ## Description
   We have a production setup with multiple local Couch databases (replicating amongst each other) syncing with a master cloud Couch database. There have been instances with documents having conflicting revision trees but for the most part, this has not caused any problems. 
   
   Our Couch databases also go through a scheduled daily purge where specific documents (after a grace period) gets purged from the database. 
   
   The issue we have observed is as follows:
   
   When a document with a conflicting revision tree is purged, it gets reverted back to the leaf revision of the conflicting revision tree. (I understand this happens because we do not specify the conflicting revision in the _purge POST request)
   
   This reverted document is caught in the next purge window and is purged again which gets rid of the document entirely from the database as expected. However, when related views are queried for data, this is not reflected; The document Id is still visible in the queried data.
   
   ## Steps to Reproduce
   Pre-requisites:
   * A document with a conflicting revision tree
   * A view that retrieves the above document Id
   
   Step 1: Purge the document, specifying the latest revision. This will revert the document to the leaf of the conflicting tree
   
   Step 2: Purge the document again, this time specifying the leaf of the conflicting tree.
   
   Step 3: Perform a purge of another document to ensure the diff between the purge sequence of the database is greater than the purge sequence of the view by more than 1. (Based on documents, this will trigger a complete rebuilding of the indexes)
   
   Step 4: Access the view. The purged document Id (now completely removed from the database) will still be returned.
   
   ## Expected Behaviour
   The view should not return Ids of documents that are purged completely.
   
   ## Your Environment
   * CouchDB Version used: CouchDB 1.6.1
   * Browser name and version: Chrome
   * Operating System and version: Ubuntu
   
   ## Additional context
   The fix that I plan on implementing is to specify all leaf revisions (including that of conflicting branches) when initiating the purge. 
   
   However, I would also like to understand what exactly is happening here for the document Id to not get removed from the index when the conflicting revision tree is purged from the database.
   
   
   

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