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From "Ashutosh Chauhan" <hashut...@apache.org>
Subject Re: Review Request 12705: HIVE-4878: With Dynamic partitioning, some queries would scan default partition even if query is not using it.
Date Mon, 22 Jul 2013 22:05:36 GMT

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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/12705/#review23657
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ql/src/java/org/apache/hadoop/hive/ql/optimizer/ppr/PartitionPruner.java
<https://reviews.apache.org/r/12705/#comment47555>

    Why are we restricting this for strict mode? We should skip default partition in all cases
unless explicitly requested by user. Assumption is default partition contains rows which were
malformed in some ways at load times and will be excluded from all further query processing.


- Ashutosh Chauhan


On July 17, 2013, 10:19 p.m., John Pullokkaran wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://reviews.apache.org/r/12705/
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> 
> (Updated July 17, 2013, 10:19 p.m.)
> 
> 
> Review request for hive and Ashutosh Chauhan.
> 
> 
> Repository: hive-git
> 
> 
> Description
> -------
> 
> With Dynamic partitioning, Hive would scan default partitions in some cases even if query
excludes it. As part of partition pruning, predicate is narrowed down to those pieces that
involve partition columns only. This predicate is then evaluated with partition values to
determine, if scan should include those partitions.
> But in some cases (like when comparing "_HIVE_DEFAULT_PARTITION_" to numeric data types)
expression evaluation would fail and would return NULL instead of true/false. In such cases
the partition is added to unknown partitions which is then subsequently scanned.
> 
> This fix avoids scanning default partition if all of the following is true:
> a) Hive dynamic partition mode is strict (hive.exec.dynamic.partition.mode=strict).
> b) partition pruning expression failed to evaluate for a given partition.
> c) at the least one of the columns in the partition is default partition.
> 
> 
> Diffs
> -----
> 
>   ql/src/java/org/apache/hadoop/hive/ql/optimizer/ppr/PartitionPruner.java 6a4a360 
>   ql/src/test/queries/clientpositive/dynamic_partition_skip_default.q PRE-CREATION 
>   ql/src/test/results/clientpositive/dynamic_partition_skip_default.q.out PRE-CREATION

> 
> Diff: https://reviews.apache.org/r/12705/diff/
> 
> 
> Testing
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> 
> Hive Unit Tests Passed.
> 
> 
> Thanks,
> 
> John Pullokkaran
> 
>


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