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https://issues.apache.org/jira/browse/HIVE-4160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13706190#comment-13706190
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Dmitriy V. Ryaboy commented on HIVE-4160:
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Jitendra,
I believe physical plan primitives for both Hive and Pig (and potentially
others) are going to come in via Tez, as both Pig and Hive want to get off
strict MR in the long-term.
I'll take a crack at extracting what's extractable. Right now Hive's UDAF
reaches fairly deeply into this code, as you noted, but I think with a little
restructuring this can be factored out.
> 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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