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POCouchdb map/reduce to return the first in a stream, then order by time
 

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  1. POCouchdb map/reduce to return the first in a stream, then order by time
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    <p>I have a couchdb which holds a series of events. Each event has an owner, an id, a time it occured and a message (plus a bunch of other stuff which doesn't matter for this exercise). I'd like a list of events which occured recently ordered by time. I looked through this question <a href="https://stackoverflow.com/questions/5198023/couchdb-filter-latest-log-per-logged-instance-from-a-list">CouchDB - filter latest log per logged instance from a list</a> and tried using it with the comparison in the reducer flipped to keep the first message (using the form where I have a complex key).</p> <p>Unfortunately it doesn't quite seem to do what want.</p> <p>Here's my map function</p> <pre><code>function(doc) { var owner, id; if (doc.owner &amp;&amp; doc.stream_id &amp;&amp; doc.message &amp;&amp; doc.receipt_time) { emit([doc.owner,doc.stream_id,doc.receipt_time], { owner: doc.owner, stream_id: doc.stream_id, timestamp: doc.receipt_time, message: doc.message }); } } </code></pre> <p>and my reduce function</p> <pre><code>function(keys, values) { var challenger, winner = null; for (var a = 0; a &lt; values.length; a++) { challenger = values[a]; if (! winner) { winner = challenger; } else { if (winner.owner !== challenger.owner &amp;&amp; winner.trace_id !== challenger.trace_id ) { return null; } else if (challenger.timestamp &lt; winner.timestamp) { winner = challenger; } } } return winner; } </code></pre> <p>Then I invoke with ?descending=true&amp;group=true&amp;group_level=2 to get the first message from each stream, however, it doesn't seem to be ordered by time, but by owner and stream_id, like this</p> <pre><code>{"rows":[ {"key":["sam","a"], "value": {"owner":"sam","stream_id":"a","timestamp":1303754236482,"message":"foo"} }, {"key":["sam","b"], "value": {"owner":"sam","stream_id":"b","timestamp":1303752578476,"message":"bar"} }, {"key":["jim","j1"], "value": {"owner":"jim","stream_id":"j1","timestamp":1303625378839,"message":"stuff"} }, {"key":["bob","loblaw"], "value": {"owner":"bob","stream_id":"loblaw","timestamp":1303328396532,"message":"more stuff"} }, {"key":["anthony","foo"], "value": {"owner":"anthony","stream_id":"foo","timestamp":1303769699444,"message":"even more"} } ]} </code></pre> <p>(Notice the final entry actually is the most recent in time).</p> <p>So what I'd like is for the final view to be what it is now but ordered by time. Is there a way to do this?</p>
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