Soliciting Feedback on Improving Server-Side Programming Documentation

Over the past few months, I've been familiarizing myself with postgres
server side programming in C.

My attempts to educate myself were slow and halting. The existing server
side programming documentation has some examples, but those examples didn't
show me how do what I wanted to do, and my research-via-google was highly
circular, almost always pointing back to the documentation I had already
found lacking, or a copy of it.

Most of what I have learned I have culled from asking people on IRC, or
bugging people I've met through user groups and PgConf. In all cases,
people have been extremely helpful. However, this method is inefficient,
because we're using two people's time, one of whom has to tolerate my
incessant questions and slow learning pace.

Furthermore, the helpful suggestions I received boiled down to:
1. The function/macro/var you're looking for is PG_FOO, git grep PG_FOO
2. Look in blah.c which does something like what you're trying to do
3. The comments in blah.h do a good job of listing and explaining this
macro or that

#1 git grep is a helpful reflex for discovering examples on my own, but it
requires that I have a term to search on in the first place, and too often
I don't know what I don't know.

#2 is the gold standard in terms of correctness (the code had to have
worked at least up to the last checkin date), and in terms of
discoverability it often gave me names of new macros to search for, coding
patterns, etc. However, I was always left with the questions: How would I
have figured this out on my own? How is the next person going to figure it
out? Why doesn't anybody document this?

#3 Often answers the last question in #2: It *is* documented, but that
documentation is not easily discoverable by conventional means.

So what I'd like to do is migrate some of the helpful information in the
header files into pages of web searchable documentation, and also to revamp
the existing documentation to be more relevant.

Along the way, I collected a list of things I wished I'd had from the start:

- A list of all the GETARG_* macros. It would have been especially great
if this were in table form: Your Parameter Is A / Use This Macro / Which
Gives This Result Type / Working example.
- A list/table of the DatumGet* macros. I'm aware that many of them
overlap/duplicate others. That'd be good to know too.
- The table at
http://www.postgresql.org/docs/9.1/static/errcodes-appendix.html has the
numeric codes and PL/PGSQL constants enumerated. It'd be nice if it had the
C #define as well
- The SPI documentation mentions most/all of the SPI functions, but I
couldn't find documentation on the SPI variables like SPI_processed and
SPI_tuptable.
- Examples and explanation of how PG_TRY()/PG_CATCH work. How to add
context callbacks.
- Direct Function Calls
- A comparison of the two modes of writing SRF functions (Materialize vs
multi-call)
- Less explanation of how to do write V0-style functions. That was
called the "old style" back in version 7.1. Why is that information up
front in the documentation when so much else is sequestered in header files?

Some of these things may seem obvious/trivial to you. I would argue that
they're only obvious in retrospect, and the more obvious-to-you things we
robustly document, the quicker we accumulate programmers who are capable of
agreeing that it's obvious, and that's good for the community.

I'm aware that some of these APIs change frequently. In those cases, I
suggest that we make note of that on the same page.

Because I'm still going through the learning curve, I'm probably the least
qualified to write the actual documentation. However, I have a clear memory
of what was hard to learn and I have the motivation to make it easier on
the next person. That makes me a good focal point for gathering,
formatting, and submitting the documentation in patch form. I'm
volunteering to do so. What I need from you is:

- Citations of existing documentation in header files that could/should
be exposed in our more formal documentation.
- Explanations of any of the things above, which I can then reformat
into proposed documentation.
- A willingness to review the proposed new documentation
- Reasoned explanations for why this is a fool's errand

You supply the expertise, I'll write the patch.

Thanks in advance.