[GitHub] [spark] wypoon commented on a change in pull request #31451: [SPARK-34338][SQL] Report metrics from Datasource v2 scan

[GitBox <gi...@apache.org>]

wypoon commented on a change in pull request #31451:
URL: https://github.com/apache/spark/pull/31451#discussion_r605995166



##########
File path: sql/catalyst/src/main/java/org/apache/spark/sql/connector/read/PartitionReader.java
##########
@@ -51,7 +51,8 @@
   T get();
 
   /**
-   * Returns an array of custom task metrics. By default it returns empty array.
+   * Returns an array of custom task metrics. By default it returns empty array. Note that it is
+   * not recommended to put heavy logic in this method as it may affect reading performance.

Review comment:
       It sounds like the DS v2 should be prepared to compute and provide the metrics whenever `PartitionReader#currentMetricsValues()` is called. I think if we always call it at the end of the task (not precluding calling it more often), we should be able to get accurate metrics.




-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

For queries about this service, please contact Infrastructure at:
users@infra.apache.org



---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org
For additional commands, e-mail: reviews-help@spark.apache.org