[ https://issues.apache.org/jira/browse/PIG-171?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Alan Gates reassigned PIG-171: ------------------------------ Assignee: Daniel Dai > Top K > ----- > > Key: PIG-171 > URL: https://issues.apache.org/jira/browse/PIG-171 > Project: Pig > Issue Type: Sub-task > Affects Versions: 0.2.0 > Reporter: Amir Youssefi > Assignee: Daniel Dai > Fix For: 0.2.0 > > Attachments: limit1.patch, limit2.patch, limit3.patch > > > Frequently, users are interested on Top results (especially Top K rows) . > This can be implemented efficiently in Pig /Map Reduce settings to deliver > rapid results and low Network Bandwidth/Memory usage. > > Key point is to prune all data on the map side and keep only small set of > rows with Top criteria . We can do it in Algebraic function (combiner) with > multiple value output. Only a small data-set gets out of mapper node. > The same idea is applicable to solve variants of this problem: > - An Algebraic Function for 'Top K Rows' > - An Algebraic Function for 'Top K' values ('Top Rank K' and 'Top Dense > Rank K') > - TOP K ORDER BY. > Another words implementation is similar to combiners for aggregate functions > but instead of one value we get multiple ones. > I will add a sample implementation for Top K Rows and possibly TOP K ORDER BY > to clarify details. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.