[SPARK-24408][SQL][DOC] Move abs function to math_funcs group

[jaceklaskowski]

What changes were proposed in this pull request?

A few math functions (abs , bitwiseNOT, isnan, nanvl) are not in math_funcs group. They should really be.

How was this patch tested?

Awaiting Jenkins

[SparkQA]

Test build #91247 has finished for PR 21448 at commit 25fe97f.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #91250 has finished for PR 21448 at commit 487a467.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[jaceklaskowski]

It is such a small change that I don't think it's going to take long to get merged. Reaching out to friendly folks to reach a consensus on it :) /cc @srowen @holdenk

[srowen]

abs does seem to belong with math functions.

isnan and nanvl are sort of math related but to me feel more like isnull. It's more about testing representations of a value, not math on them (NaN isn't a mathematical notion, note). I'd leave it. Those methods in the JDK aren't in java.lang.Math, FWIW.

bitwiseNOT sure seems like an odd man out. The other bitwise functions are defined in Column.scala I don't see why, other than that 'not' is a unary operator. This came from #5867 (diff) but looks like that was a comment about functions.py. Although its location is odd, I guess I'd leave it unless @Shiti or @rxin say it's OK to move.

[holdenk]

If it’s ok I’ll take a quick look at this on Friday as discussed with Jacek.

[rxin]

I'd only move abs and nothing else.

[holdenk]

So, I personally don't have strong feelings about which groups these functions should be in, but just a reminder we should unify with PySpark with whatever our decision is.

In PySpark bitwiseNot is under math, abs is currently grouped with some string operators. Less important since its just code organization there but while were thinking about it anyways.

[holdenk]

@jaceklaskowski how would you feel about just moving abs as suggested by @rxin?

[holdenk]

Cool, let me know when you get a chance to update the PR @jaceklaskowski :)

[holdenk]

LGTM

[holdenk]

Merged to master

[SparkQA]

Test build #92437 has finished for PR 21448 at commit d11dbb9.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #92438 has finished for PR 21448 at commit 2bbc750.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.