[exim] A way to fetch retry config from postgres

Hello.

I'm trying to fetch the retry portion of exim4.conf from a postgres
database.
The portion is this default string:

*                      *           F,2h,15m; G,16h,1h,1.5; F,14d,6h

I've read the retry configuration examples (
https://www.exim.org/exim-html-current/doc/html/spec_html/ch-retry_configuration.html)
which does not have a mention of that possible and wasn't able to find a
way to accomplish that.
What I've tried myself were these constructions:

data='${lookup pgsql{select config.retry from config}{$value}}'

and

${lookup pgsql{select config.retry from config}{$value}}

I always have the same error:

unknown or malformed retry error "pgsql{select"

The question is - is this possible and if it is, what am I doing wrong?

Thank you.