Add support for DISTINCT in STRING_AGG functions for PostgreSQL

[christxph]

Hi,

Exposed does not support using the DISTINCT keyword in STRING_AGG functions for Postgres (groupConcat in Exposed) as it's explicitly disable in PostgreSQL.kt#L36:

Exposed/exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/PostgreSQL.kt

Line 36 in 5908c40

expr.distinct -> tr.throwUnsupportedException("PostgreSQL doesn't support DISTINCT in STRING_AGG function.")

However, Postgres supports using DISTINCT in STRING_AGG functions for a while now (couldn't find the exact version).

Does anything speak against implementing this in Exposed?

Thanks.

[Tapac]

Thank you for the info as I wasn't able to find such information in the official doc, also Order by clause is supported too.