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https://issues.apache.org/jira/browse/DRILL-6763?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16638078#comment-16638078
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ASF GitHub Bot commented on DRILL-6763:
---------------------------------------

vvysotskyi commented on a change in pull request #1481: DRILL-6763: Codegen 
optimization of SQL functions with constant values
URL: https://github.com/apache/drill/pull/1481#discussion_r222601096
 
 

 ##########
 File path: 
exec/java-exec/src/main/java/org/apache/drill/exec/expr/EvaluationVisitor.java
 ##########
 @@ -590,109 +635,84 @@ private HoldingContainer 
visitReturnValueExpression(ReturnValueExpression e, Cla
     public HoldingContainer visitQuotedStringConstant(QuotedString e, 
ClassGenerator<?> generator)
         throws RuntimeException {
       MajorType majorType = e.getMajorType();
-      JBlock setup = generator.getBlock(BlockType.SETUP);
       JType holderType = generator.getHolderType(majorType);
       JVar var = generator.declareClassField("string", holderType);
-      JExpression stringLiteral = JExpr.lit(e.value);
-      JExpression buffer = 
generator.getMappingSet().getIncoming().invoke("getContext").invoke("getManagedBuffer");
-      setup.assign(var,
-          
generator.getModel().ref(ValueHolderHelper.class).staticInvoke("getVarCharHolder").arg(buffer).arg(stringLiteral));
-      return new HoldingContainer(majorType, var, null, null);
+      generator.declareSetterMethod(
+        var,
+        buffer -> ValueHolderHelper.getVarCharHolder(buffer, e.value));
 
 Review comment:
   Please replace `e.value` with `e.getString()`.

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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: Major
>             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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