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From "Robert Newson (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COUCHDB-1367) When settings revs_limit on db - the db increases its update_seq counter when viewing stats - but not when getting changes
Date Fri, 23 Dec 2011 09:40:30 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-1367?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13175357#comment-13175357
] 

Robert Newson commented on COUCHDB-1367:
----------------------------------------

On reflection, it's couchdb-lucene's bug, not couchdb's. Let me explain.

CouchDB-Lucene (to give it its grown-up name) compares the update_seq from a GET /dbname to
the sequences a background process is indexing through. It then unblocks searcher threads
as that process reaches or exceeds the required update_seq. This is, in fact, just silly.

Instead, a search query should cause a GET /dbname/_changes?since=<latest index checkpoint>.
It should block until it consumes the entire response, passing the updates to the indexing
process. It can then return a non-stale search result. In the case that the index is fresh,
the _changes response contains no rows, and serves only to confirm that the index is fresh.
If, as planned, CouchDB-Lucene *also* runs a _changes?feed=continuous to keep indexes fresh
in the background then indexes will simply be fresher than they would be in the CouchDB case.

I repeat, CouchDB-Lucene's *mistake* is to *only* use the feed=continuous variety of the changes
feed. This prevents it from knowing when its own index is fresh.

I will make this change next week and I suggest that this ticket be closed with no further
action taken.

                
> When settings revs_limit on db - the db increases its update_seq counter when viewing
stats - but not when getting changes
> --------------------------------------------------------------------------------------------------------------------------
>
>                 Key: COUCHDB-1367
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-1367
>             Project: CouchDB
>          Issue Type: Bug
>          Components: HTTP Interface
>    Affects Versions: 1.1.1
>         Environment: Any
>            Reporter: Henrik Hofmeister
>            Assignee: Bob Dionne
>            Priority: Minor
>              Labels: revs_limit
>
> If you put a number to _revs_limit on a db (to update it) - the http://host/dbname/ info
document gets an increase in update_seq number - however the changes feed does not contain
this change (while its not a change). This causes the update_seq in the dbinfo doc and the
last seq in the changes feed to differ - which breaks any application depending on the update_seq
number as the expected sequence size of the db (in my case - couchdb-lucene that will only
respond to stale requests because it thinks its not up to date)
> I know this is an edge case - but still its something fairly fundamental - that clearly
is not working as intended. 

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