From fd2bc0e26134b7d74fe33da99eab6623a9859f22 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Sun, 23 Mar 2025 15:33:05 +0900
Subject: [PATCH v4 1/2] Add support for custom_query_jumble at field-level

This option gives the possibility for query jumbling to force custom
jumbling policies specific to a field of a node.  When dealing with
complex node structures, this is simpler than having to enforce a custom
function across the full node.

Custom functions need to be defined as _jumble${node}_${field}, are
given in input the parent node and the field value.  The field value is
not really required if we have the parent Node, but it makes custom
implementations easier to follow with field-specific definitions and
values.  The code generated by gen_node_support.pl uses a macro called
JUMBLE_CUSTOM(), that hides the objects specific to queryjumblefuncs.c.
---
 src/include/nodes/nodes.h             |  4 ++++
 src/backend/nodes/gen_node_support.pl | 15 +++++++++++++--
 src/backend/nodes/queryjumblefuncs.c  |  6 ++++++
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index d18044b4e650..adec68a45ab8 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -54,6 +54,7 @@ typedef enum NodeTag
  *   readfuncs.c.
  *
  * - custom_query_jumble: Has custom implementation in queryjumblefuncs.c.
+ *   Available as well as a per-field attribute.
  *
  * - no_copy: Does not support copyObject() at all.
  *
@@ -101,6 +102,9 @@ typedef enum NodeTag
  * - equal_ignore_if_zero: Ignore the field for equality if it is zero.
  *   (Otherwise, compare normally.)
  *
+ * - custom_query_jumble: Has custom implementation in queryjumblefuncs.c
+ *   applied for the field of a node.  Available as well as a node attribute.
+ *
  * - query_jumble_ignore: Ignore the field for the query jumbling.  Note
  *   that typmod and collation information are usually irrelevant for the
  *   query jumbling.
diff --git a/src/backend/nodes/gen_node_support.pl b/src/backend/nodes/gen_node_support.pl
index 7e3f335ac09d..2d62ecb1d9d6 100644
--- a/src/backend/nodes/gen_node_support.pl
+++ b/src/backend/nodes/gen_node_support.pl
@@ -471,6 +471,7 @@ foreach my $infile (@ARGV)
 								&& $attr !~ /^read_as\(\w+\)$/
 								&& !elem $attr,
 								qw(copy_as_scalar
+								custom_query_jumble
 								equal_as_scalar
 								equal_ignore
 								equal_ignore_if_zero
@@ -1283,12 +1284,17 @@ _jumble${n}(JumbleState *jstate, Node *node)
 		my $t = $node_type_info{$n}->{field_types}{$f};
 		my @a = @{ $node_type_info{$n}->{field_attrs}{$f} };
 		my $query_jumble_ignore = $struct_no_query_jumble;
+		my $query_jumble_custom = 0;
 		my $query_jumble_location = 0;
 		my $query_jumble_squash = 0;
 
 		# extract per-field attributes
 		foreach my $a (@a)
 		{
+			if ($a eq 'custom_query_jumble')
+			{
+				$query_jumble_custom = 1;
+			}
 			if ($a eq 'query_jumble_ignore')
 			{
 				$query_jumble_ignore = 1;
@@ -1304,8 +1310,13 @@ _jumble${n}(JumbleState *jstate, Node *node)
 		}
 
 		# node type
-		if (($t =~ /^(\w+)\*$/ or $t =~ /^struct\s+(\w+)\*$/)
-			and elem $1, @node_types)
+		if ($query_jumble_custom)
+		{
+			# Custom function that applies to one field of a node.
+			print $jff "\tJUMBLE_CUSTOM($n, $f);\n";
+		}
+		elsif (($t =~ /^(\w+)\*$/ or $t =~ /^struct\s+(\w+)\*$/)
+			   and elem $1, @node_types)
 		{
 			# Squash constants if requested.
 			if ($query_jumble_squash)
diff --git a/src/backend/nodes/queryjumblefuncs.c b/src/backend/nodes/queryjumblefuncs.c
index 189bfda610aa..9b9cf6f34381 100644
--- a/src/backend/nodes/queryjumblefuncs.c
+++ b/src/backend/nodes/queryjumblefuncs.c
@@ -333,6 +333,12 @@ do { \
 	if (expr->str) \
 		AppendJumble(jstate, (const unsigned char *) (expr->str), strlen(expr->str) + 1); \
 } while(0)
+/*
+ * Note that the argument types are enforced for the per-field custom
+ * functions.
+ */
+#define JUMBLE_CUSTOM(nodetype, item) \
+	_jumble##nodetype##_##item(jstate, expr, expr->item)
 
 #include "queryjumblefuncs.funcs.c"
 
-- 
2.49.0