标签：style blog class code java tar
A = LOAD ‘/user/input/t.txt‘ as (k:chararray,c:int); B = group A BY k; C = foreach B generate group,SUM(A.c); store C into ‘/user/output/test1.out‘; DUMP C; store C into ‘/user/output/test2.out‘;
A = LOAD ‘/user/input/t.txt‘ as (k:chararray,c:int); B = group A BY k; C = foreach B generate group,SUM(A.c); store C into ‘/user/output/test1.out‘; store C into ‘/user/output/test2.out‘;
With multi-query execution Pig processes an entire script or a batch of statements at once.Will create a batch Job to process the data
Turning it On or Off
Multi-query execution is turned on by default. To turn it off and revert to Pig‘s "execute-on-dump/store" behavior, use the "-M" or "-no_multiquery" options.
To run script "myscript.pig" without the optimization, execute Pig as follows:
$ pig -M myscript.pig or $ pig -no_multiquery myscript.pig
the first code will produce three mapred Job for:
1.store C into ‘/user/output/test1.out‘
2.DUMP C
3.store C into ‘/user/output/test2.out‘
while the seconde code will only produce:one mapred Job
if we run the second code by: pig -no_multiquery test.pig it will also produce two Jobs
Store vs. Dump
With multi-query exection, you want to use STORE to save (persist) your results. You do not want to use DUMP as it will disable multi-query execution and is likely to slow down execution. (If you have included DUMP statements in your scripts for debugging purposes, you should remove them.)
Pig —Multi-Query Execution,布布扣,bubuko.com
标签：style blog class code java tar
原文地址：http://blog.csdn.net/xiewenbo/article/details/24978333
