[SPARK-5685] Show warning when users open text files compressed with non-splittable algorithms like gzip - ASF JIRA

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Details

Type: Improvement
Status: Resolved
Priority: Minor
Resolution: Incomplete
Affects Version/s: None
Fix Version/s: None
Component/s: Spark Core
Labels:
- bulk-closed

Description

This is a usability or user-friendliness issue.

It's extremely common for people to load a text file compressed with gzip, process it, and then wonder why only 1 core in their cluster is doing any work.

Some examples:

I'm not sure how this problem can be generalized, but at the very least it would be helpful if Spark displayed some kind of warning in the common case when someone opens a gzipped file with sc.textFile.