I started a similar thread with probably similar concerns:
I believe this effort should be done. I added to my TODO list to
compile a list of used functions in a selection of picked extensions to
use that as a starting point of an "API".
Álvaro Hernández Tortosa
On 15/03/16 13:02, Corey Huinker wrote:
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
* 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
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
* 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
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.