GitHub user paul-rogers opened a pull request:
https://github.com/apache/drill/pull/660
Drill 5052: Option to debug generated Java code using an IDE
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.
This PR modifies the code generation path to optionally allow "plain-old
Java" compilation: the generated code becomes a subclass of the template. The
generated code can then be compiled as a plain-old Java class with no byte-code
fix-up. A further option allows writing 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 provides an option to do the above, enabled by developers when needed.
The existing byte-code technique is used for production code generation.
Included are a few examples from the External Sort Batch that shows the
kinds of minor fix-ups that might be needed for a template in order for the
"plain-old Java" technique to work.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/paul-rogers/drill DRILL-5052
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/drill/pull/660.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #660
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commit 5af6bf038baea373fa2faeb0db3c5bac997bf3ec
Author: Paul Rogers <[email protected]>
Date: 2016-11-20T02:29:24Z
DRILL-5052: Hygiene
Fixes some broken toString( ) methods in code generation classes
Fixes a variety of small compilation warnings
Adds Java doc to a few classes
commit 39fdec1544e7356a936c36f06598217cfa43a1bc
Author: Paul Rogers <[email protected]>
Date: 2016-11-20T02:45:17Z
DRILL-5052: Implementation
Provides a second compilation path for generated code: âplan old Javaâ
in which generated code inherit from their templates. Such code can be
compiled directly, allowing easy debugging of generated code.
commit 6f2f4039c4b0ecbd722420cf25fc3a8b98d6106a
Author: Paul Rogers <[email protected]>
Date: 2016-11-20T02:54:04Z
DRILL-5052: Examples
Shows how to generate two classes in the External Sort Batch as âplain
old Javaâ to enable IDE debugging of that generated code. Required
minor clean-up of the templates.
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