A = LOAD'/user/input/t.txt' as (k:chararray,c:int);B = group A BY k;C = foreach Bgenerate group,SUM(A.c);store C into'/user/output/test1.out';DUMP C;store C into'/user/output/test2.out...

Use OptimizationPig supports various optimization rules which are turned on by default. Become familiar with these rules.Use TypesIf types are not specified in the load statement, Pig as

Timing your UDFsThe first step to improving performance and efficiency is measuring where the time is going. Pig provides a light-weight method for approximately measuring how much time is spent i

STOREStores or saves results to the file system.SyntaxSTORE alias INTO 'directory' [USING function];TermsaliasThe name of a relation.INTORequired keyword.'directory'

setShows/Assigns values to keys used in Pig.Syntaxset [key 'value']TermskeyKey (see table). Case sensitive.valueValue for key (see tab

Pig- MultiQuery Execution

pig wordcount analysis

OverviewEval FunctionsHow to Use a Simple Eval FunctionHow to Write a Simple Eval FunctionAggregate FunctionsFilter FunctionsPig TypesSchemaError HandlingFunction OverloadingReporting ProgressImpo

什么是Skewed Join？MapReduce是一个分布式的处理系统，不同的key会经过map处理以后发往不同的reduce，但是有一种可能是有一个key特别大，因为key是相同的是分不开的，如果有一个特别大会造成一个reduce运行特别缓慢，消耗非常多的内存。我们采取的方式是把超大key也分散到不同的reduce里面做。Pig对skewed  join的是先有三个步骤，第一个是通过Samp

pig 调试（explain&illerstrate）

Specialized JoinsPig Latin includes three "specialized" joins: replicated joins, skewed joins, and merge joins.Replicated, skewed, and merge joins can be performed using inner joins.Replicat

grunt> cat t.txtkw1     2kw3     1kw2     4kw1     5kw2     2