chern opened a new pull request, #4609:
URL: https://github.com/apache/datafusion-comet/pull/4609
## Which issue does this PR close?
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Closes #3737.
## Rationale for this change
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Similar change to #3738.
Comet uses `Class.forName(className)` to reflectively load Iceberg classes.
The single-argument `Class.forName` uses the classloader of the calling
class, not the thread context classloader.
When the Comet JAR is placed in Spark's `jars/` folder, it is loaded by the
system classloader.
However, Iceberg classes may be bundled inside the user's application jar
(as uber jar), which is loaded by Spark's [application
classloader](https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/deploy/SparkSubmit.scala#L939-L950)
.
Since parent classloaders cannot see classes loaded by child classloaders,
`Class.forName` from Comet's code fails with `ClassNotFoundException`.
## What changes are included in this PR?
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- Replaces bare `Class.forName()` calls in `CometScanRule` with the
`IcebergReflection.loadClass()` helper method.
## How are these changes tested?
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- Verified in a deployment where the Comet jar is in Spark's `jars/` folder
and Iceberg is bundled in the application's uber jar; ran a few SQL queries
that involved reading from Iceberg.
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