[ https://issues.apache.org/jira/browse/PIG-981?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Pradeep Kamath resolved PIG-981. -------------------------------- Resolution: Duplicate Fixed in https://issues.apache.org/jira/browse/PIG-953?focusedCommentId=12761760&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#action_12761760 > Merge join should restrict join key expressions to simple projects > ------------------------------------------------------------------ > > Key: PIG-981 > URL: https://issues.apache.org/jira/browse/PIG-981 > Project: Pig > Issue Type: Bug > Affects Versions: 0.4.0 > Reporter: Pradeep Kamath > Assignee: Pradeep Kamath > > Currently merge join allows join key expressions to be arbitrary expressions > with the assumption that the expressions keep the sort order. Since currently > only ascending sort order is supported, the code checks at run times for sort > order and catches the case where sort order is broken because the join key > expression is not order preserving. However there is a reason we should > restrict the join keys to projection of columns only: > PIG-953 will enable pig to perform merge join to work with loaders and > store functions which can internally index sorted data. These store functions > can only create an index (and hence lookup on the index) on raw data columns > (and not expressions on the columns). > Hopefully this does not downgrade the usability of merge join much since if > the expressions can always be applied post join on the join columns and since > the expressions are order preserving they do not affect the outcome of the > join. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.