Remove useless entries for aggregate functions from fmgrtab.c.

Gen_fmgrtab.pl treated aggregate functions the same as other built-in
functions, which is wasteful because there is no real need to have
entries for them in the fmgr_builtins[] table.  Suppressing those
entries saves about 3KB in the compiled table on my machine; which
is not a lot but it's not nothing either, considering that that
table is pretty "hot".  The only outside code change needed is
that ExecInitWindowAgg() can't be allowed to call fmgr_info_cxt()
on a plain aggregate function.  But that saves a few cycles anyway.

Having done that, the aggregate_dummy() function is unreferenced
and might as well be dropped.  Using "aggregate_dummy" as the prosrc
value for an aggregate is now just a documentation convention not
something that matters.  There was some discussion of using NULL
instead to save a few bytes in pg_proc, but we'd have to remove
prosrc's BKI_FORCE_NOT_NULL marking which doesn't seem a great idea.
Anyway, it's possible there's client-side code that expects to
see "aggregate_dummy" there, so I'm loath to change it without a
strong reason.

Discussion: https://postgr.es/m/533989.1604263665@sss.pgh.pa.us

1 files changed, 7 insertions, 2 deletions

diff --git a/src/backend/utils/Gen_fmgrtab.pl b/src/backend/utils/Gen_fmgrtab.pl
index 8228ad6db60..ae8cf5bb64c 100644
--- a/src/backend/utils/Gen_fmgrtab.pl
+++ b/src/backend/utils/Gen_fmgrtab.pl
@@ -75,6 +75,7 @@ foreach my $row (@{ $catalog_data{pg_proc} })
 		oid    => $bki_values{oid},
 		name   => $bki_values{proname},
 		lang   => $bki_values{prolang},
+		kind   => $bki_values{prokind},
 		strict => $bki_values{proisstrict},
 		retset => $bki_values{proretset},
 		nargs  => $bki_values{pronargs},
@@ -195,8 +196,10 @@ foreach my $s (sort { $a->{oid} <=> $b->{oid} } @fmgr)
 	$sqlname .= "_" . $s->{args} if ($proname_counts{ $s->{name} } > 1);
 	$sqlname =~ s/\s+/_/g;
 	print $ofh "#define F_" . uc $sqlname . " $s->{oid}\n";
-	# We want only one extern per internal-language function
-	if ($s->{lang} eq 'internal' && !$seenit{ $s->{prosrc} })
+	# We want only one extern per internal-language, non-aggregate function
+	if (   $s->{lang} eq 'internal'
+		&& $s->{kind} ne 'a'
+		&& !$seenit{ $s->{prosrc} })
 	{
 		$seenit{ $s->{prosrc} } = 1;
 		print $pfh "extern Datum $s->{prosrc}(PG_FUNCTION_ARGS);\n";
@@ -214,6 +217,8 @@ my $fmgr_count       = 0;
 foreach my $s (sort { $a->{oid} <=> $b->{oid} } @fmgr)
 {
 	next if $s->{lang} ne 'internal';
+	# We do not need entries for aggregate functions
+	next if $s->{kind} eq 'a';
 
 	print $tfh ",\n" if ($fmgr_count > 0);
 	print $tfh