Re: PostgreSQL Service Name Enhancement - Wildcard support for LDAP/DNS lookup

Tom,

I believe there are two main concerns that you raise, addressed below:

First:

> It needs to be a more constrained syntax.
> One possibility is to insist that the wildcard be only a part
> of the name string, eg
>
> [myservers-%]
> host=%.domain.com
> port=5433
> user=admin

* This counter-proposal is getting closer to the more complex matching requirements that I was attempting to de-scope, but it should certainly be considered. I can see where someone may want to have a different LDAP/DNS domain or something like that through prefix convention, though we would likely want to restrict to one "%" symbol in the service definition, yes? I am fine with including this capability in the patch, provided the general [%] case is still supported (see below for expanded reasons).

Second:

> since we check service names
> before other possibilities such as host/database names, the entry would
> then proceed to capture every possible connection request

* I should have explicitly covered the case where no service name is provided at connection time - If a service name is not specified in the connection string/connection parameters at all, I would propose that this wildcard entry not match (even if service names are processed first) and normal processing proceed. As a comparable, the '%' in a like statement doesn't match a NULL after all. I don't think having a blank replacement value would make much sense either. Please inform me if I am not addressing some part of your concern with this mindset.

Some additional comments:

* It is in fact is desirable for us (and likely others) to capture all service names in one entry; I expect to utilize it exclusively once implemented. I would like to look up all service name entries from a single LDAP location if a previous entry in the file does not short circuit the match. To do this, I am explicitly looking to use a [%] entry in our service name file - the prefix requirement is not consistent with our environmental requirements. The service name file is a client construct that can be overridden by the caller if they desire, but keep in mind that this type of feature is targeted for controlled/managed environments.

* Adding additional processing logic for 'myserver-%' would only make this more flexible for other use cases and would certainly meet the goals of this proposal, so I am fine including it in scope if the [%] is also allowed per above. When these other wildcard w/ prefix entries can match above the general [%] entry, it could be compelling (see my first email regarding entry order considerations). Those not wanting the [%] could choose to not implement it and stick to something closer to the prefix approach you have in mind.

Summary of Open Questions:

* (From Above) For prefix wildcards, OK to restrict to one % replacement?

* Do the above points address initial concerns regarding service names being processed before host/db names?

* If both prefix/non-prefix are allowed, what should be the behavior for cases where [prefix-%] matches and fails to connect/lookup and then [%] is also located further down?
** Without additional discussion, I would assume that it would attempt a connection for consistency. Again, people can choose to not use both features together. Another option would be to somehow introduce a "stop processing" flag in the service entries on connection/lookup failures, which may be generally useful even when wild cards are not in use.

Thanks for the reply and your thoughts on this proposal so far. I am looking forward to the continued conversation.

Bryan