Re: [PATCH] Add some documentation on how to call internal functions

Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
> I'll mark this patch as ready for committer

I spent a little time looking at this. I agree that it's better to
show conversion of the example function's arguments to and from text*
rather than leaving them as Datum. I also do think that we need to
incorporate the example into src/tutorial, if only because that
provides a chance to test it. And indeed, testing exposed that the
example doesn't work:

$ cd src/tutorial
$ make
$ psql postgres
psql (18devel)
Type "help" for help.

postgres=# \i funcs.sql

psql:funcs.sql:152: ERROR: could not determine which collation to use for string comparison
HINT: Use the COLLATE clause to set the collation explicitly.

The problem here is that we failed to pass through the result of
PG_GET_COLLATION() to text_starts_with. We could do that, certainly,
for a couple more lines of code. But it feels like this is getting
into details that obscure the main point. I wonder if it'd be better
to choose a different example that calls a non-collation-dependent
target function.

Anyway, proposed v3 attached. I folded the two patches into one,
and editorialized on the text a little.

regards, tom lane