From e7cd0c62015170a87b8cf037a998e8711f1a40a9 Mon Sep 17 00:00:00 2001
From: Andrey Pyzhikov <5071@mail.ru>
Date: Fri, 25 Feb 2022 08:46:03 +0800
Subject: [PATCH 1/2] Checking if the subquery uses the same object as the main
 query

Signed-off-by: Andrey Pyzhikov <5071@mail.ru>
---
 system/Database/BaseBuilder.php            |  4 ++++
 tests/system/Database/Builder/BaseTest.php | 12 ++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/system/Database/BaseBuilder.php b/system/Database/BaseBuilder.php
index ccfa5bd9d8bb..842aae3c8a29 100644
--- a/system/Database/BaseBuilder.php
+++ b/system/Database/BaseBuilder.php
@@ -2763,6 +2763,10 @@ protected function buildSubquery($builder, bool $wrapped = false, string $alias
             $builder($builder = $this->db->newQuery());
         }
 
+        if ($builder === $this) {
+            throw new DatabaseException('The subquery cannot be the same object as the main query object.');
+        }
+
         $subquery = strtr($builder->getCompiledSelect(), "\n", ' ');
 
         if ($wrapped) {
diff --git a/tests/system/Database/Builder/BaseTest.php b/tests/system/Database/Builder/BaseTest.php
index 1390e4668200..5a2a4f1578db 100644
--- a/tests/system/Database/Builder/BaseTest.php
+++ b/tests/system/Database/Builder/BaseTest.php
@@ -11,6 +11,7 @@
 
 namespace CodeIgniter\Database\Builder;
 
+use CodeIgniter\Database\Exceptions\DatabaseException;
 use CodeIgniter\Test\CIUnitTestCase;
 use CodeIgniter\Test\Mock\MockConnection;
 
@@ -53,4 +54,15 @@ public function testGetTableIgnoresFrom()
         $result = $builder->getTable();
         $this->assertSame('jobs', $result);
     }
+
+    public function testSubquerySameBaseBuilderObject()
+    {
+        $this->expectException(DatabaseException::class);
+        $this->expectExceptionMessage('The subquery cannot be the same object as the main query object.');
+
+        $builder = $this->db->table('users');
+
+        $builder->fromSubquery($builder, 'sub');
+        $builder->getCompiledSelect();
+    }
 }

From e5bc03d8037fc1791ef912a85938fd0dabdfd00c Mon Sep 17 00:00:00 2001
From: Andrey Pyzhikov <5071@mail.ru>
Date: Sat, 26 Feb 2022 07:59:09 +0800
Subject: [PATCH 2/2] Update tests/system/Database/Builder/BaseTest.php

Co-authored-by: kenjis <kenji.uui@gmail.com>
---
 tests/system/Database/Builder/BaseTest.php | 1 -
 1 file changed, 1 deletion(-)

diff --git a/tests/system/Database/Builder/BaseTest.php b/tests/system/Database/Builder/BaseTest.php
index 5a2a4f1578db..c7386066aa74 100644
--- a/tests/system/Database/Builder/BaseTest.php
+++ b/tests/system/Database/Builder/BaseTest.php
@@ -63,6 +63,5 @@ public function testSubquerySameBaseBuilderObject()
         $builder = $this->db->table('users');
 
         $builder->fromSubquery($builder, 'sub');
-        $builder->getCompiledSelect();
     }
 }