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https://issues.apache.org/jira/browse/DRILL-5052?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul Rogers updated DRILL-5052:
-------------------------------
    Description: 
Drill makes extensive use of Java code generation to implement its operators. 
Drill uses sophisticated techniques to blend generated code with pre-compiled 
template code. An unfortunate side-effect of this behavior is that it is very 
difficult to visualize and debug the generated code.

As it turns out, Drill's code-merge facility is, in essence, a do-it-yourself 
version of subclassing. The Drill "template" is the parent class, the generated 
code is the subclass. But, rather than using plain-old subclassing, Drill 
combines the code from the two classes into a single "artificial" packet of 
byte codes for which no source exists.

Modify the code generation path to optionally allow "plain-old Java" 
compilation: the generated code is a subclass of the template. Compile the 
generated code as a plain-old Java class with no byte-code fix-up. Write the 
code to a known location that the IDE can search when looking for source files.

With this change, developers can turn on the above feature, set a breakpoint in 
a template, then step directly into the generated Java code called from the 
template.

This feature should be an option, enabled by developers when needed. The 
existing byte-code technique should be used for production code generation.

  was:
Drill makes extensive use of Java code generation to implement its operators. 
Drill uses sophisticated techniques to blend generated code with pre-compiled 
template code. An unfortunate down-site of this behavior is that it is very 
difficult to visualize and debug the generated code.

As it turns out, Drill's code-merge facility is, in essence, a do-it-yourself 
version of subclassing. The Drill "template" is the parent class, the generated 
code is the subclass. But, rather than using plain-old subclassing, Drill 
combines the code from the two classes into a single "artificial" packet of 
byte codes for which no source exists.

Modify the code generation path to optionally allow "plain-old Java" 
compilation: the generated code is a subclass of the template. Compile the 
generated code as a plain-old Java class with no byte-code fix-up. Write the 
code to a known location that the IDE can search when looking for source files.

With this change, developers can turn on the above feature, set a breakpoint in 
a template, then step directly into the generated Java code called from the 
template.

This feature should be an option, enabled by developers when needed. The 
existing byte-code technique should be used for production code generation.


> Option to debug generated Java code using an IDE
> ------------------------------------------------
>
>                 Key: DRILL-5052
>                 URL: https://issues.apache.org/jira/browse/DRILL-5052
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Execution - Codegen
>    Affects Versions: 1.8.0
>            Reporter: Paul Rogers
>            Assignee: Paul Rogers
>            Priority: Minor
>
> Drill makes extensive use of Java code generation to implement its operators. 
> Drill uses sophisticated techniques to blend generated code with pre-compiled 
> template code. An unfortunate side-effect of this behavior is that it is very 
> difficult to visualize and debug the generated code.
> As it turns out, Drill's code-merge facility is, in essence, a do-it-yourself 
> version of subclassing. The Drill "template" is the parent class, the 
> generated code is the subclass. But, rather than using plain-old subclassing, 
> Drill combines the code from the two classes into a single "artificial" 
> packet of byte codes for which no source exists.
> Modify the code generation path to optionally allow "plain-old Java" 
> compilation: the generated code is a subclass of the template. Compile the 
> generated code as a plain-old Java class with no byte-code fix-up. Write the 
> code to a known location that the IDE can search when looking for source 
> files.
> With this change, developers can turn on the above feature, set a breakpoint 
> in a template, then step directly into the generated Java code called from 
> the template.
> This feature should be an option, enabled by developers when needed. The 
> existing byte-code technique should be used for production code generation.



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