[SPARK-14878][SQL] Adding examples for Trim characters string function

[kevinyu98]

What changes were proposed in this pull request?

This pr is a follow-up PR for this merged trim function pr: Support Trim characters in the string trim function.

I am adding examples in the ExpressionDescription session for stringTrim function

How was this patch tested?

This is documentation pr, and it passed all sql testing locally.

[srowen]

You need a new JIRA

[HyukjinKwon]

I'd fold those lines into one if possible. If that looks quite messed, we could add each extra newline between _FUNC_(...)s. Currently, the doc is rendered as below:

[kevinyu98]

I see, thanks for finding this. I put the extra line there, then run this below

cd sql
create-docs.sh

it generate doc like this.

trim

trim(str) - Removes the leading and trailing space characters from str

trim(BOTH trimStr FROM str) - Remove the leading and trailing trimStr characters from str

trim(LEADING trimStr FROM str) - Remove the leading trimStr characters from str

trim(TRAILING trimStr FROM str) - Remove the trailing trimStr characters from str

and this is how describe function show:

spark-sql> describe function extended trim;
Function: trim
Class: org.apache.spark.sql.catalyst.expressions.StringTrim
Usage: 
    trim(str) - Removes the leading and trailing space characters from `str`

    trim(BOTH trimStr FROM str) - Remove the leading and trailing `trimStr` characters from `str`

    trim(LEADING trimStr FROM str) - Remove the leading `trimStr` characters from `str`

    trim(TRAILING trimStr FROM str) - Remove the trailing `trimStr` characters from `str`
  
Extended Usage:
    Arguments:
      * str - a string expression
      * trimStr - the trim string characters to trim, the default value is a single space
      * BOTH, FROM - these are keywords to specify trimming string characters from both ends of the string
      * LEADING, FROM - these are keywords to specify trimming string characters from the left end of the string
      * TRAILING, FROM - these are keywords to specify trimming string characters from the right end of the string
  
    Examples:
      > SELECT trim('    SparkSQL   ');
       SparkSQL
      > SELECT trim('SL', 'SSparkSQLS');
       parkSQ
      > SELECT trim(BOTH 'SL' FROM 'SSparkSQLS');
       parkSQ
      > SELECT trim(LEADING 'SL' FROM 'SSparkSQLS');
       parkSQLS
      > SELECT trim(TRAILING 'SL' FROM 'SSparkSQLS');
       SSparkSQ
  
Time taken: 1.924 seconds, Fetched 4 row(s)
17/09/22 01:06:39 INFO SparkSQLCLIDriver: Time taken: 1.924 seconds, Fetched 4 row(s)

[kevinyu98]

@srowen sure, I will open a new JIRA for this.

[HyukjinKwon]

ok to test

[SparkQA]

Test build #82074 has finished for PR 19302 at commit 795f41a.

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

[kevinyu98]

I am opening a new jira SPARK-22088 for this. I will close this PR. The style fails is because a new JIRA SPARK-22088 fixed a style issue after I submit my PR. I have included that JIRA in my new PR.