[ https://issues.apache.org/jira/browse/PIG-2395?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Daniel Dai resolved PIG-2395. ----------------------------- Resolution: Duplicate This is a duplication of PIG-1324. It involves some significant rework of column prune optimizer. > Pig doesn't do early projection for some scripts > ------------------------------------------------ > > Key: PIG-2395 > URL: https://issues.apache.org/jira/browse/PIG-2395 > Project: Pig > Issue Type: Improvement > Affects Versions: 0.9.1 > Environment: Linux > Reporter: Jie Li > > For some scripts Pig doesn't do early projection, e.g. dropping non-necessary > fields as soon as possible. This is observed in two ways: 1) the output > doesn't contain INFO like "ColumnPruneVisitor - Columns pruned for xxx: $0, > $1"; 2) the job has as much or more local IO (see FILE_BYTES_READ and > FILE_BYTES_WRITTEN) as HDFS IO (see HDFS_BYTES_READ). > One example where Pig should figure out A's fields c~n can be dropped before > the COGROUP. > A = load '/tmp/A' USING PigStorage('|') as (a,b,c,d,e,f,g,h,i,j,k,l,m,n); > B = load '/tmp/B' USING PigStorage('|') as (a); > COG = cogroup A by a, B by a; > out = foreach COG generate SUM(A.b) as sum; > store out into '/tmp/out' USING PigStorage('|'); > Another similar example involves a GROUP operator. > While Pig is able and assumed to do early projection in most cases, this > inconsistency hurts the performance badly. -- 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