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https://issues.apache.org/jira/browse/DRILL-6763?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16628634#comment-16628634
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ASF GitHub Bot commented on DRILL-6763:
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vvysotskyi edited a comment on issue #1481: DRILL-6763: Codegen optimization of
SQL functions with constant values
URL: https://github.com/apache/drill/pull/1481#issuecomment-424684441
If this fix just improves the performance without any consequences, then
there is no need to disable it or specify an option for that.
But in any case, it is useful to see numbers.
Regarding the unit test, generate a query with large string literals, so
they will be specified in the methods in generated code, and query should fail
with "code too large" compile exception.
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> Codegen optimization of SQL functions with constant values
> ----------------------------------------------------------
>
> Key: DRILL-6763
> URL: https://issues.apache.org/jira/browse/DRILL-6763
> Project: Apache Drill
> Issue Type: Improvement
> Components: Execution - Codegen
> Affects Versions: 1.14.0
> Reporter: shuifeng lu
> Assignee: shuifeng lu
> Priority: Critical
> Fix For: 1.15.0
>
> Attachments: Query1.java, Query2.java, code_compare.png,
> compilation_time.png
>
>
> Codegen class compilation takes tens to hundreds of milliseconds, a class
> cache is hit when generifiedCode of code generator is exactly the same.
> It works fine when UDF only takes columns or symbols, but not efficient when
> one or more parameters in UDF is always distinct from the other.
> Take face recognition for example, the face images are almost distinct from
> each other according to lighting, facial expressions and details.
> It is important to reduce redundant class compilation especially for those
> low latency queries.
> Cache miss rate and metaspace gc can also be reduced by eliminating the
> redundant classes.
> Here is the query to get the persons whose last name is Brunner and hire from
> 1st Jan 1990:
> SELECT full_name, hire_date FROM cp.`employee.json` where last_name =
> 'Brunner' and hire_date >= '1990-01-01 00:00:00.0';
> Now get the persons whose last name is Bernard and hire from 1st Jan 1990.
> SELECT full_name, hire_date FROM cp.`employee.json` where last_name =
> 'Bernard' and hire_date >= '1990-01-01 00:00:00.0';
> Figure !compilation_time.png! shows the compilation time of the generated
> code by the above query in FilterRecordBatch on my laptop
> Figure !code_compare.png! shows the only difference of the generated code
> from the attachments is the last_name value at line 156.
> It is straightforward that the redundant class compilation can be eliminated
> by making the string12 as a member of the class and set the value when the
> instance is created
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