[BUG] pgbench nested \if conditions incorrectly processed

From 873028c217b4353f482d8c43a3eddd3521bfe370 Mon Sep 17 00:00:00 2001
From: nkey <michail.nikolaev@gmail.com>
Date: Sun, 15 Dec 2024 14:04:26 +0100
Subject: [PATCH v1] pgbench: Fix nested if/elif/else handling in scripts

Add support for properly handling nested conditional blocks in pgbench scripts
by correctly tracking the state of inner conditional blocks when they appear
inside skipped (false) branches. Previously, the evaluation of conditions in
nested blocks could lead to incorrect behavior.

Add a regression test to verify nested if/elif/else statements work as
expected.
---
 src/bin/pgbench/meson.build                 |  1 +
 src/bin/pgbench/pgbench.c                   | 10 +++-
 src/bin/pgbench/t/003_pgbench_nested_ifs.pl | 57 +++++++++++++++++++++
 3 files changed, 66 insertions(+), 2 deletions(-)
 create mode 100644 src/bin/pgbench/t/003_pgbench_nested_ifs.pl

diff --git a/src/bin/pgbench/meson.build b/src/bin/pgbench/meson.build
index d330bb5eb0d..ac45cad4015 100644
--- a/src/bin/pgbench/meson.build
+++ b/src/bin/pgbench/meson.build
@@ -43,6 +43,7 @@ tests += {
     'tests': [
       't/001_pgbench_with_server.pl',
       't/002_pgbench_no_server.pl',
+      't/003_pgbench_nested_ifs.pl',
     ],
   },
 }
diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c
index c4c38099c5b..5181629133e 100644
--- a/src/bin/pgbench/pgbench.c
+++ b/src/bin/pgbench/pgbench.c
@@ -3880,8 +3880,14 @@ advanceConnectionState(TState *thread, CState *st, StatsData *agg)
 						switch (conditional_stack_peek(st->cstack))
 						{
 							case IFSTATE_FALSE:
-								if (command->meta == META_IF ||
-									command->meta == META_ELIF)
+								if (command->meta == META_IF)
+								{
+									/* nested if in skipped branch - ignore */
+									conditional_stack_push(st->cstack,
+														   IFSTATE_IGNORED);
+									st->command++;
+								}
+								else if (command->meta == META_ELIF)
 								{
 									/* we must evaluate the condition */
 									st->state = CSTATE_START_COMMAND;
diff --git a/src/bin/pgbench/t/003_pgbench_nested_ifs.pl b/src/bin/pgbench/t/003_pgbench_nested_ifs.pl
new file mode 100644
index 00000000000..52bc1734e06
--- /dev/null
+++ b/src/bin/pgbench/t/003_pgbench_nested_ifs.pl
@@ -0,0 +1,57 @@
+# Copyright (c) 2021-2024, PostgreSQL Global Development Group
+
+# Test nested if/elif/else working correctly in pgbench
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+
+use Test::More;
+
+my ($node, $result);
+
+$node = PostgreSQL::Test::Cluster->new('pgbench_nested_ifs');
+$node->init;
+$node->start;
+
+$node->pgbench(
+	'--no-vacuum --client=1 --exit-on-abort --transactions=1',
+	0,
+	[qr{actually processed}],
+	[qr{^$}],
+	'nested ifs',
+	{
+		'pgbench_nested_if' => q(
+			\if false
+				SELECT 1 / 0;
+				\if true
+					SELECT 1 / 0;
+				\elif true
+					SELECT 1 / 0;
+				\else
+					SELECT 1 / 0;
+				\endif
+				SELECT 1 / 0;
+			\elif false
+				\if true
+					SELECT 1 / 0;
+				\elif true
+					SELECT 1 / 0;
+				\else
+					SELECT 1 / 0;
+				\endif
+			\else
+				\if false
+					SELECT 1 / 0;
+				\elif false
+					SELECT 1 / 0;
+				\else
+					SELECT 'correct';
+				\endif
+			\endif
+		)
+	});
+
+$node->stop;
+done_testing();
-- 
2.43.0