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https://issues.apache.org/jira/browse/HIVE-8188?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14140232#comment-14140232
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Prasanth J commented on HIVE-8188:
----------------------------------
I tried to avoid this reflection invocation multiple times in inner loop by
computing total aggregation size once and reusing it in inner loop. I ran the
following query
{code}
select ss_quantity, ss_store_sk, ss_promo_sk, count(ss_list_price),
count(ss_sales_price), sum(ss_ext_sales_price) from store_sales_orc group by
ss_quantity,ss_store_sk,ss_promo_sk;
{code}
store_sales had 2880404 rows. The original execution time was 18.5s and with
the above changes the time went down to 15.5s which is ~17% gain which explains
the reflection cost from the attached image.
> ExprNodeGenericFuncEvaluator::_evaluate() loads class annotations in a tight
> loop
> ---------------------------------------------------------------------------------
>
> Key: HIVE-8188
> URL: https://issues.apache.org/jira/browse/HIVE-8188
> Project: Hive
> Issue Type: Bug
> Components: UDF
> Affects Versions: 0.14.0
> Reporter: Gopal V
> Attachments: udf-deterministic.png
>
>
> When running a near-constant UDF, most of the CPU is burnt within the VM
> trying to read the class annotations for every row.
> !udf-deterministic.png!
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