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Hive >> mail # user >> Cartesian product detection in the query plan?


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David Morel 2013-01-28, 09:39
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Re: Cartesian product detection in the query plan?
Iirc hive.mapred.mode strict should prevent this. If not we should add it.

On Monday, January 28, 2013, David Morel <[EMAIL PROTECTED]> wrote:
> Hi everyone,
>
> I had to kill some queries that were taking forever, and it turns out
> they were doing cartesian products (missing ON clause on a JOIN).
>
> I wonder how I could see that in the EXPLAIN output (which I still find
> a bit cryptic). Specifically, the stage that it was stuck in was this:
>
>   Stage: Stage-7
>     Map Reduce
>       Alias -> Map Operator Tree:
>         $INTNAME
>             Reduce Output Operator
>               sort order:
>               tag: 1
>               value expressions:
>                     expr: _col1
>                     type: int
>         $INTNAME1
>             Reduce Output Operator
>               sort order:
>               tag: 0
>               value expressions:
>                     expr: _col0
>                     type: bigint
>                     expr: _col1
>                     type: string
>       Reduce Operator Tree:
>         Join Operator
>           condition map:
>                Inner Join 0 to 1
>           condition expressions:
>             0 {VALUE._col0} {VALUE._col1}
>             1 {VALUE._col1}
>           handleSkewJoin: false
>           outputColumnNames: _col0, _col1, _col3
>           File Output Operator
>             compressed: true
>             GlobalTableId: 0
>             table:
>                 input format:
org.apache.hadoop.mapred.SequenceFileInputFormat
>                 output format:
org.apache.hadoop.hive.ql.io.HiveSequenceFileOutputFormat
>
> Is there anything in there that should have alerted me?
>
> I found out by looking at the query, but I wonder if the query plan (if
> I could read it) would have given me that information.
>
> Thanks a lot
>
> David Morel
>
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David Morel 2013-01-28, 16:45
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Edward Capriolo 2013-01-28, 16:58
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David Morel 2013-01-28, 17:16
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Dean Wampler 2013-01-28, 17:05
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB