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From "Adam Kocoloski (JIRA)" <j...@apache.org>
Subject [jira] Commented: (COUCHDB-462) track conflict count in db_info (was built-in conflicts view)
Date Tue, 01 Feb 2011 14:14:28 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-462?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12989212#comment-12989212
] 

Adam Kocoloski commented on COUCHDB-462:
----------------------------------------

Hi Bob, thanks.  I see a couple of problems with the patch:

1) https://github.com/bdionne/couchdb/commit/31a5672#L2R337

It looks like you're incrementing when deleted=true, rather than false.

2) https://github.com/bdionne/couchdb/commit/31a5672#L2R331

I think you're double-counting by passing N + NextN to count_non_deleted/2.

More broadly, and in the context of COUCHDB-988, I'm wondering if many of these key tree operations
could benefit from a refactoring that adds a generalized couch_key_tree:fold function.  I
believe Randall Leeds wrote such a thing at one point in time.  I'm picturing a fold that
supports short-circuiting, possibly using the {ok, _} and {stop, _} tagged tuples convention
from couch_btree.

... Actually, digressing a bit further, I'm curious if anyone has ever considered the tradeoffs
of different methods of short-circuiting.  The tagged tuples are one approach, but it could
also be implemented with erlang:throw/1.  I'd expect that when short-circuiting is rare throwing
an exception is the preferred approach because it creates less garbage along the way.  I'm
not sure what would be best when short-circuiting is routine (e.g. in the btree).

> track conflict count in db_info (was built-in conflicts view)
> -------------------------------------------------------------
>
>                 Key: COUCHDB-462
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-462
>             Project: CouchDB
>          Issue Type: Improvement
>          Components: HTTP Interface
>            Reporter: Adam Kocoloski
>             Fix For: 1.2
>
>         Attachments: 462-jan-2.patch, COUCHDB-462-adam-updated.patch, COUCHDB-462-jan.patch,
conflicts_in_db_info.diff, conflicts_in_db_info2.diff, conflicts_view.diff, whitespace.diff
>
>
> This patch adds a built-in _conflicts view indexed by document ID that looks like
> GET /dbname/_conflicts
> {"rows":[
> {"id":"foo", "rev":"1-1aa8851c9bb2777e11ba56e0bf768649", "conflicts":["1-bdc15320c0850d4ee90ff43d1d298d5d"]}
> ]}
> GET /dbname/_conflicts?deleted=true
> {"rows":[
> {"id":"bar", "rev":"5-dd31186f5aa11ebd47eb664fb342f1b1", "conflicts":["5-a0efbb1990c961a078dc5308d03b7044"],
"deleted_conflicts":["3-bdc15320c0850d4ee90ff43d1d298d5d","2-cce334eeeb02d04870e37dac6d33198a"]},
> {"id":"baz", "rev":"2-eec205a9d413992850a6e32678485900", "deleted":true, "deleted_conflicts":["2-10009b36e28478b213e04e71c1e08beb"]}
> ]}
> As the HTTPd and view layers are a bit outside my specialty I figured I should ask for
a Review before Commit.

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