Re: PQHost() undefined behavior if connecting string contains both host and hostaddr types

On Mon, Mar 26, 2018 at 10:47 PM, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>
wrote:

> updated patch attached with additional doc updates as per the suggestion
> from the upthreads.
>
​---------------------------------------------------------
Some comments if the patch remains in-tact:
​
​Lower-case "i" in "It is not" in the second paragraphs

The ... function returns NULL when the input conn parameter is NULL or an
empty string if conn cannot be evaluated. Otherwise, the return value is
the first non-NULL, non-empty, value of either the host or hostaddr
property of conn. <omit the entire last sentence, Callers of this
function..., for PQport too>

Omit "properly" after established - if the connection is established one
can assume it was done "properly".

Add "the" after calling: "can be checked by calling the
<function>PQstatus</function> function.

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I'm having a bit of concern about the actual specification and
wording...but don't have time right now to thoroughly read the thread
history, docs, and/or code at this moment to know whether its just
inexperience on my part or an actual confusion. But here's where I'm at
presently...

I'm not sure why there is confusion here in the first place...the docs[1]
say:

https://www.postgresql.org/docs/10/static/libpq-status.html
"The following functions return parameter values established at connection."

At which point there is only one meaningful value for them - the value that
pertains to the established connection.

As far as "or an empty string if conn cannot be evaluated" should just
become "an empty string if conn is inactive".

----------------------------
Another odd piece is:

https://www.postgresql.org/docs/10/static/libpq-connect.html#LIBPQ-MULTIPLE-HOSTS
"The value for host is ignored unless the authentication method requires
it, in which case it will be used as the host name."

There is no coverage of "1 host, many hostaddr; n host, n hostaddr; and n
host, m hostaddr" combinations - namely which are valid and how the NxM
combination would even work if it is even allowed.

Then, if we do connect using hostaddr, and authenticate with host, should
we indicate that fact in the PQhost output or not?

Potentially PQhost would be defined to return an actual hostname if it can
figure one out - even if the active connection was made using hostaddr. My
take is that PQhost is meant to be user-informative rather than technical,
and should ever only return the single most appropriate value it can
compute. Just need to decide on the logic for determining "appropriate"
then document and implement it.

-----------------------------
Also at: https://www.postgresql.org/docs/10/static/libpq-status.html
"The following functions return parameter values established at connection.
These values are fixed for the life of the connection. If a multi-host
connection string is used, the values of PQhost, PQport, and PQpass can
change if a new connection is established using the same PGconn object.
Other values are fixed for the lifetime of the PGconn object."

Maybe something like:

The following functions return parameters values established at connection
and, except for the multi-valued fail-over accessors PQhost and PQport, as
well as PQpass, cannot change during the lifetime of the PGconn object.

PQpass is a bit odd here given its not multi-valued...not sure what if
anything to make of that.

David J.