[SPARK-16207] order guarantees for DataFrames

• Type: Documentation
• Status: Resolved
• Priority: Minor
• Resolution: Incomplete
• Affects Version/s: 1.6.1
• Component/s: Spark Core
• Labels: bulk-closed
• Assignee: Unassigned
• Reporter: Max Moroz
• Created: 25/Jun/16 08:27
• Updated: 21/May/19 04:16
• Resolved: 21/May/19 04:16

Description

There's no clear explanation in the documentation about what guarantees are available for the preservation of order in DataFrames. Different blogs, SO answers, and posts on course websites suggest different things. It would be good to provide clarity on this.

Examples of questions on which I could not find clarification:
1) Does groupby() preserve order?
2) Does take() preserve order?
3) Is DataFrame guaranteed to have the same order of lines as the text file it was read from? (Or as the json file, etc.)