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https://issues.apache.org/jira/browse/SPARK-20456?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15983590#comment-15983590
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Michael Patterson commented on SPARK-20456:
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I saw that there are short docstrings for the aggregate functions, but I think
it can be unclear for people new to Spark, or relational algebra. For example,
some of my coworkers didn't know you could do, for example,
`df.agg(mean(col))`, without doing a `groupby`. There are also no links to
`groupby` in any of the aggregate functions. I also didn't know about
`collect_set` for a long time. I think adding examples would help with
visibility and understanding.
The same things applies to `lit`. It took me a while to learn what it did.
For the datetime stuff, for example this line has a column named 'd':
https://github.com/map222/spark/blob/master/python/pyspark/sql/functions.py#L926
I think it would be more informative to name it 'date' or 'time'.
Do these sound reasonable?
> Document major aggregation functions for pyspark
> ------------------------------------------------
>
> Key: SPARK-20456
> URL: https://issues.apache.org/jira/browse/SPARK-20456
> Project: Spark
> Issue Type: Documentation
> Components: Documentation
> Affects Versions: 2.1.0
> Reporter: Michael Patterson
> Priority: Minor
>
> Document `sql.functions.py`:
> 1. Document the common aggregate functions (`min`, `max`, `mean`, `count`,
> `collect_set`, `collect_list`, `stddev`, `variance`)
> 2. Rename columns in datetime examples.
> 3. Add examples for `unix_timestamp` and `from_unixtime`
> 4. Add note to all trigonometry functions that units are radians.
> 5. Document `lit`
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