[jira] [Commented] (ARROW-12710) [C++] String concatenate aggregate kernel

["Niranda Perera (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-12710?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17359401#comment-17359401 ] 

Niranda Perera commented on ARROW-12710:
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[~icook] I checked the postgres string_agg (https://www.postgresqltutorial.com/postgresql-aggregate-functions/postgresql-string_agg-function/). It seems to have an `order_by` option. Do you we need that part as well? If not, AFAIU, this would be a straight-forward scalar agg kernel, and I can take it up. :)

> [C++] String concatenate aggregate kernel
> -----------------------------------------
>
>                 Key: ARROW-12710
>                 URL: https://issues.apache.org/jira/browse/ARROW-12710
>             Project: Apache Arrow
>          Issue Type: New Feature
>          Components: C++
>            Reporter: Ian Cook
>            Priority: Major
>
> Like MySQL/Impala {{group_concat}} and PostgreSQL {{string_agg}}. Takes a string array and a separator (possibly optional?) and returns one scalar string (one per group in the case of group aggregation) representing all the string values in the array concatenated together, with the separator added between each pair of concatenated values.
> For example, in the case of no grouping and using separator {{"-"}}, this would take input:
> {code}
> Array<string>
> [ 
>   "foo",
>   "bar",
>   "baz"
> ]
> {code}
> and return the following string scalar as output:
> {code}
> "foo-bar-baz"
> {code}
>  



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