[jira] [Created] (DRILL-7001) Documentation - renaming columns name in csv header

["benj (JIRA)" <ji...@apache.org>]

benj created DRILL-7001:
---------------------------

             Summary: Documentation - renaming columns name in csv header
                 Key: DRILL-7001
                 URL: https://issues.apache.org/jira/browse/DRILL-7001
             Project: Apache Drill
          Issue Type: Wish
    Affects Versions: 1.15.0
            Reporter: benj


Don't know how if this is the best place for this request but,

Some operation are realized that eventually change the name of the column when requesting a csvh file (with header),
 These operations are not documented.
 Although it's possible to read [HeaderBuilder.java|https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/store/easy/text/compliant/HeaderBuilder.java], It will be interesting to create a section in documentation to explain at least the principle of these different cases to avoid stupid problems/difficulties

List of operations (maybe not exhaustive) :
 * Trim() on CSV column name
{noformat}
 Name , Age,PoB  , Info
=>
`Name`, `Age`, `PoB` and `Info`{noformat}

 * Others characters than [a-zA-Z0-9_] are replace by '_' (underscore)
{noformat}
Name,Sum$,em@il
=>
`Name`,'`Sum_`,`em_il`{noformat}

 * Fieldname starting with '_' (underscore) are prefixed by 'col'
{noformat}
_name,_age_,pob_,_col_
=>
`col_name`, `col_age_`, `pob_`, `col_col_`{noformat}

 * Fieldname starting with [^a-zA-Z] are prefixed 'col_'
{noformat}
0_name, 1_age,@pob,#other1,'other2'
=>
`col_0_name`, `col_1_age`, `col_pob`, `col_other1`, `col_other2_`{noformat}

 *  Quotation marks are removed
 * If char is unique
 ** if [a-zA-Z] do nothing
 ** elif [0-9] prefix with col_
 ** else reanme in column_[0-9]+ where [0-9]+ designs the position of the column
 * Duplicate columns names (case insensitive) are suffixed with _[0-9]+ (starting from "_2")
{noformat}
0_name,col_0_name,colx,COLX,colx,colx_2
=>
`col_0_name`, `col_0_name_2`, `colx`, `COLX_2`, `colx_3`, `colx_2_2`{noformat}

 



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