[GitHub] [spark] beliefer edited a comment on issue #24535: [SPARK-27640][SQL][SS] Avoid duplicate lookups for datasource through provider

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beliefer edited a comment on issue #24535: [SPARK-27640][SQL][SS] Avoid duplicate lookups for datasource through provider
URL: https://github.com/apache/spark/pull/24535#issuecomment-493852958
 
 
   > Thank you for ping me, @beliefer . However, the reviewers' comments are consistent. And, I also agree with that. AFAIK, you didn't provide more evidences for your claim about the performance problem. Without evidence, we can not make a progress. Could you investigate more and give us some numbers for your claim?
   > 
   > > you know that it includes some Java SPI, traversing and reflection.
   > > I think there exists a little performance problems.
   
   Thanks for your reply. @dongjoon-hyun.  AFAIK, java reflection will result in significant performance issue.
   The oracle website`https://docs.oracle.com/javase/tutorial/reflect/index.html` contains some description about performance:
   ```
   Performance Overhead
   Because reflection involves types that are dynamically resolved, certain Java virtual machine optimizations can not be performed. Consequently, reflective operations have slower performance than their non-reflective counterparts, and should be avoided in sections of code which are called frequently in performance-sensitive applications.
   ```
   `https://blog.frankel.ch/performance-cost-of-reflection/` contains performance cost test.
   `https://stackoverflow.com/questions/435553/java-reflection-performance` has discussion of java reflection.

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