Re: comments in argument list of plpgsql get stripped? - Mailing list pgsql-general

Hi David,

> The fact that you can write comments in the middle of the arguments in an
> artifact of the parser and likely there is not reasonable way to get them to
> persist.

"Artifact" as in "something not normally used"?

> You either want to use "COMMENT ON" like Raymond said or you can
> simply move the comments into the body of the function.

I already use the COMMENT ON to give each function a general description, an overview of what it does, which - imho -
fitsthe scope of the COMMENT ON being a comment on the whole function, rather than a particular part of, like the body,
partof the body or the argument list. 

As I showed in my example the comments within the function body gets stored and retrieved like one usually expects. Up
untilinvestigating whether I can put comments on the arguments directly in the argument list, I stored all this
informationat the head of the body, where the audit trail of the function body lives, too. However I thought about
puttingall the stuff where it logically belongs, to have a sound design. 

> The relevant table
> that stores the function stores everything except the body as individual
> fields so that it can facilitate dependency tracking and type verification,
> etc...  In order to do this the input needs to be stripped of all comments
> and newlines/control-characters so that only syntactically meaningful
> content remains.

I see your point and now understand the reason why PostgreSQL behaves the way it does, that is: stripping the comments
fromthe argument list, storing the comments within the function body. 

> The fundamental issue is that the input arguments to a function are stored
> as an array on pg_proc and thus to do not have their own OID with which to
> link onto pg_description.
>
> The fundamental question is by what means do you expect to be able to view
> and/or modify these comments?

As PostgreSQL silently accepts these comments in the argument list, I expected them to be retrievable later on, not
caringhow and where they are stored, but believing that they are stored. 
I fully understand that for the ease of parsing and having a "usable" argument list, PostgreSQL stores the argument
listinternally differently than the argument list is presented to the user and I don't dare to argue about it, because
Iaccept the fact and assume it's not only to due performance, but also to be able to use this meta information in the
databasedictionary to write queries about it (something I appreciate!). 

> Feel free to provide thoughts and suggestions regarding how core could be
> modified to fit your intended use-case but I would offer that unless you are
> willing to fund and/or do the work that it isn't going to get much attention
> due apparent need to modify the catalogs and introduce a total new way of
> dealing with comments.  It is not the current policy of PostgreSQL to
> capture and store original DDL but instead it parsers the DDL into the
> needed catalog entries and then recombines the entries into a "normalized"
> form when necessary (e.g., for pg_dump).

Well, first of all it was important to me to know that in fact I did the right thing and PostgreSQL behaves as
expected,not making an obvious mistake on the syntax of comments. 
Futhermore, now that I know its the expected way, I know how to circumvent it, looking for other means of documenting
theargument list in a sound way, like including the comments at the head of the function's body, like I already did. 

Second, not knowing about the internals of the comment system of PostgreSQL and how argument lists are handled: -

How about having something like:

I) COMMENT ON <function> (arglist-qualifier).<argumentname> IS '<comment>';  (or something similar)

and

II) Having PostgreSQL issuing a NOTICE that "comments get stripped" if you use comments somewhere where PostgreSQL
acceptsthem, but discards them silently? 

Best regards,
  Ralph