Adding argument names to aggregate functions

Hi hackers,

I'm sure I'm not the only one who can never remember which way around
the value and delimiter arguments go for string_agg() and has to look it
up in the manual every time. To make it more convenient, here's a patch
that adds proargnames to its pg_proc entries so that it can be seen with
a quick \df in psql.

I also added names to json(b)_object_agg() for good measure, even though
they're more obvious. The remaining built-in multi-argument aggregate
functions are the stats-related ones, where it's all just Y/X (but why
in that order?), so I didn't think it was necessary. If others feel more
strongly, I can add those too.

- ilmari

From 73f323d5e97dca2e2452f5be199864a8358559c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dagfinn=20Ilmari=20Manns=C3=A5ker?= <ilmari@ilmari.org>
Date: Mon, 27 Feb 2023 13:06:29 +0000
Subject: [PATCH] Add argument names to multi-argument aggregates

This makes it easier to see which way around the arguments go when
using \dfa.  This is particularly relevant for string_agg(), but add
it to json(b)_object_agg() too for good measure.
---
 src/include/catalog/pg_proc.dat | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index e2a7642a2b..f96d29278f 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -4988,6 +4988,7 @@
 { oid => '3538', descr => 'concatenate aggregate input into a string',
   proname => 'string_agg', prokind => 'a', proisstrict => 'f',
   prorettype => 'text', proargtypes => 'text text',
+  proargnames => '{value,delimiter}',
   prosrc => 'aggregate_dummy' },
 { oid => '3543', descr => 'aggregate transition function',
   proname => 'bytea_string_agg_transfn', proisstrict => 'f',
@@ -5000,6 +5001,7 @@
 { oid => '3545', descr => 'concatenate aggregate input into a bytea',
   proname => 'string_agg', prokind => 'a', proisstrict => 'f',
   prorettype => 'bytea', proargtypes => 'bytea bytea',
+  proargnames => '{value,delimiter}',
   prosrc => 'aggregate_dummy' },
 
 # To ASCII conversion
@@ -8899,6 +8901,7 @@
 { oid => '3197', descr => 'aggregate input into a json object',
   proname => 'json_object_agg', prokind => 'a', proisstrict => 'f',
   provolatile => 's', prorettype => 'json', proargtypes => 'any any',
+  proargnames => '{key,value}',
   prosrc => 'aggregate_dummy' },
 { oid => '3198', descr => 'build a json array from any inputs',
   proname => 'json_build_array', provariadic => 'any', proisstrict => 'f',
@@ -9791,6 +9794,7 @@
 { oid => '3270', descr => 'aggregate inputs into jsonb object',
   proname => 'jsonb_object_agg', prokind => 'a', proisstrict => 'f',
   prorettype => 'jsonb', proargtypes => 'any any',
+  proargnames => '{key,value}',
   prosrc => 'aggregate_dummy' },
 { oid => '3271', descr => 'build a jsonb array from any inputs',
   proname => 'jsonb_build_array', provariadic => 'any', proisstrict => 'f',
-- 
2.39.1