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https://issues.apache.org/jira/browse/PIG-4797?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15363626#comment-15363626
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liyunzhang_intel commented on PIG-4797:
---------------------------------------
Let's explain more about why we can not put JoinGroupOptimizerSpark before
CombinerOptimizer?
The CombinerOptimizer will collapse POGlobalRearrange and POPackager into
POReduceBy like following:
{code:title=origin}
foreach (using algebraicOp)
-> packager
-> globalRearrange
-> localRearrange
{code}
{code:title=After CombinerOptimization}
foreach (using algebraicOp.Final)
-> reduceBy (uses algebraicOp.Intermediate)
-> localRearrange
-> foreach (using algebraicOp.Initial)
-> CombinerRearrange
{code}
The JoinGroupOptimizaterSpark will collapse POLocalRearrange,
POGlobalRearrange, POPackage into POJoinGroupSpark
{code:title=origin}
foreach
-> packager
->globalRearrange
->localRearrange
->load
{code}
{code:title=JoinGroupOptimization}
foreach
->joinGroupSpark
->load
{code}
if JoinGroupOptimizerSpark first, the spark plan will be changed and the spark
plan will not be suitable for CombinerOptimizer any more.
> Optimization for join/group case for spark mode
> -----------------------------------------------
>
> Key: PIG-4797
> URL: https://issues.apache.org/jira/browse/PIG-4797
> Project: Pig
> Issue Type: Sub-task
> Components: spark
> Reporter: Pallavi Rao
> Assignee: liyunzhang_intel
> Labels: spork
> Attachments: Join performance analysis.pdf, PIG-4797.patch,
> PIG-4797_2.patch, PIG-4797_3.patch, PIG-4797_5.patch
>
>
> There are a big performance difference in join between spark and mr mode.
> {code}
> daily = load './NYSE_daily' as (exchange:chararray, symbol:chararray,
> date:chararray, open:float, high:float, low:float,
> close:float, volume:int, adj_close:float);
> divs = load './NYSE_dividends' as (exchange:chararray, symbol:chararray,
> date:chararray, dividends:float);
> jnd = join daily by (exchange, symbol), divs by (exchange, symbol);
> store jnd into './join.out';
> {code}
> join.sh
> {code}
> mode=$1
> start=$(date +%s)
> ./pig -x $mode $PIG_HOME/bin/join.pig
> end=$(date +%s)
> execution_time=$(( $end - $start ))
> echo "execution_time:"$excution_time
> {code}
> The execution time:
> || |||mr||spark||
> |join|20 sec|79 sec|
> You can download the test data NYSE_daily and NYSE_dividends in
> https://github.com/alanfgates/programmingpig/blob/master/data/
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