I don't think a union is required for this to make sense. On Jun 11, 2012, at 11:58 AM, "Daniel Dai (JIRA)" <j...@apache.org> wrote:
> > [ > https://issues.apache.org/jira/browse/PIG-2747?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13292983#comment-13292983 > ] > > Daniel Dai commented on PIG-2747: > --------------------------------- > > My understanding is there is a union after T1, T2, right? > > Yes we only merge the consecutive filter into "and" condition. We don't merge > "or" condition. So you want > > filter cond1, filter cond2 -> union ==> filter cond1 or cond2 > >> Support more predicate pushdown to a data source by pulling up multiple >> predicates from branches using the same data source >> --------------------------------------------------------------------------------------------------------------------------- >> >> Key: PIG-2747 >> URL: https://issues.apache.org/jira/browse/PIG-2747 >> Project: Pig >> Issue Type: Improvement >> Reporter: Yu Xu >> Priority: Minor >> >> consider the following example: >> T = load ... ; >> T1 = filter T by col == 'hello'; >> T2 = filter T by col =='world'; >> currently Pig optimizer does not combine the two predicates and cannot push >> down the predicates to the data sources (via LoadMetadata). Thus the data >> source cannot do any filtering. A full table/file scan is required. >> A current more efficient workaround (by hand) is to rewrite the above script >> to the following equivalent one: >> T = load ...; >> T = filter T by col == 'hello' or col == 'world' ; >> T1 = filter T by col == 'hello'; >> T2 = filter T by col == 'world'; >> the above script enables Pig to push down the predicate (col == 'hello' or >> col == 'world') to the data source to use available partitions/indexes for >> potentially much more efficient processing. >> This JIRA is created to request PIG optimizer to perform the above type of >> optimization automatically. > > -- > This message is automatically generated by JIRA. > If you think it was sent incorrectly, please contact your JIRA > administrators: > https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa > For more information on JIRA, see: http://www.atlassian.com/software/jira > >
