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From "Vinod Kumar Vavilapalli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-4160) Vectorized Query Execution in Hive
Date Thu, 04 Jul 2013 07:30:20 GMT

    [ https://issues.apache.org/jira/browse/HIVE-4160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13699820#comment-13699820
] 

Vinod Kumar Vavilapalli commented on HIVE-4160:
-----------------------------------------------

A huge +1 to that. Having a common set of operators will be a huge win. That said, I already
see that the current branch follows Hive's operator base classes, uses HiveConf etc. I believe
with little effort, this can be cleaned and pulled apart into one separate maven module that
everyone can use.

Some points to think about:
 - The target location of the module. The dependency graph can become un-wieldly.
 - Given the use of base Operator, OperatorDesc etc from Hive, if at all there is interest
and commitment, we should do this ASAP when we only have a handful of operators.
 - Make one other project demonstrate how it can be reused across ecosystem projects, PIG
will be great - just a few operators will be a great start 

Thoughts?
                
> Vectorized Query Execution in Hive
> ----------------------------------
>
>                 Key: HIVE-4160
>                 URL: https://issues.apache.org/jira/browse/HIVE-4160
>             Project: Hive
>          Issue Type: New Feature
>            Reporter: Jitendra Nath Pandey
>            Assignee: Jitendra Nath Pandey
>         Attachments: Hive-Vectorized-Query-Execution-Design.docx, Hive-Vectorized-Query-Execution-Design-rev2.docx,
Hive-Vectorized-Query-Execution-Design-rev3.docx, Hive-Vectorized-Query-Execution-Design-rev3.docx,
Hive-Vectorized-Query-Execution-Design-rev3.pdf, Hive-Vectorized-Query-Execution-Design-rev4.docx,
Hive-Vectorized-Query-Execution-Design-rev4.pdf, Hive-Vectorized-Query-Execution-Design-rev5.docx,
Hive-Vectorized-Query-Execution-Design-rev5.pdf, Hive-Vectorized-Query-Execution-Design-rev6.docx,
Hive-Vectorized-Query-Execution-Design-rev6.pdf, Hive-Vectorized-Query-Execution-Design-rev7.docx,
Hive-Vectorized-Query-Execution-Design-rev8.docx, Hive-Vectorized-Query-Execution-Design-rev8.pdf,
Hive-Vectorized-Query-Execution-Design-rev9.docx, Hive-Vectorized-Query-Execution-Design-rev9.pdf
>
>
> The Hive query execution engine currently processes one row at a time. A single row of
data goes through all the operators before the next row can be processed. This mode of processing
is very inefficient in terms of CPU usage. Research has demonstrated that this yields very
low instructions per cycle [MonetDB X100]. Also currently Hive heavily relies on lazy deserialization
and data columns go through a layer of object inspectors that identify column type, deserialize
data and determine appropriate expression routines in the inner loop. These layers of virtual
method calls further slow down the processing. 
> This work will add support for vectorized query execution to Hive, where, instead of
individual rows, batches of about a thousand rows at a time are processed. Each column in
the batch is represented as a vector of a primitive data type. The inner loop of execution
scans these vectors very fast, avoiding method calls, deserialization, unnecessary if-then-else,
etc. This substantially reduces CPU time used, and gives excellent instructions per cycle
(i.e. improved processor pipeline utilization). See the attached design specification for
more details.

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