Re: correction suggestion for https://www.postgresql.org/docs/17/auth-username-maps.html

Thanks.  My goal of trying to be a bit more precise regarding the \1 reference is probably counter-productive.  The existing wording makes me ask "why" to which the answer is "because if database-username is a regexp a reference to \1 resolves to any capturing groups it defines; and if there are none the regexp will be malformed and break when you attempt to reload pg_hba.conf".  But that is a lot of words for something that is unlikely to be encountered in practice and does distract the reader from the main point.

(Likewise, the system-username regexp can contain more than one capture - which are only available later in the system-username regexp - though again it seems unlikely anyone is going to use that feature in this context.)

I'm good with this.

Thanks!

David J.