From 6d32ffcc6c7352dfa5f752fa5866394dfc0594ca Mon Sep 17 00:00:00 2001
From: Ankush Menat <ankush@frappe.io>
Date: Fri, 2 May 2025 11:51:11 +0530
Subject: [PATCH] perf: optimize `!=` operator when field can be null

---
 frappe/model/db_query.py      | 3 +++
 frappe/tests/test_db_query.py | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/frappe/model/db_query.py b/frappe/model/db_query.py
index 04c4b4e95f..c5e8e1115f 100644
--- a/frappe/model/db_query.py
+++ b/frappe/model/db_query.py
@@ -924,6 +924,9 @@ from {tables}
 			# intersection instead of full table scans.
 			if fallback == value and f.operator == "=":
 				condition = f"( {column_name} is NULL OR {column_name} {f.operator} {value} )"
+			elif fallback == value and f.operator == "!=":
+				# NULL != anything is always NULL, so won't match
+				condition = f"{column_name} {f.operator} {value}"
 			else:
 				condition = f"ifnull({column_name}, {fallback}) {f.operator} {value}"
 
diff --git a/frappe/tests/test_db_query.py b/frappe/tests/test_db_query.py
index 25d59d66ff..7b43201407 100644
--- a/frappe/tests/test_db_query.py
+++ b/frappe/tests/test_db_query.py
@@ -1200,6 +1200,14 @@ class TestDBQuery(IntegrationTestCase):
 		query = frappe.get_all("DocField", {"fieldname": None}, run=0)
 		self.assertIn("''", query)
 		self.assertNotIn("\\'", query)
+		self.assertNotIn("ifnull", query)
+
+	def test_ifnull_fallback_types(self):
+		query = frappe.get_all("DocField", {"fieldname": ("!=", None)}, run=0)
+		# Fallbacks should always be of correct type
+		self.assertIn("''", query)
+		self.assertNotIn("0", query)
+		self.assertNotIn("ifnull", query)
 
 
 class TestReportView(IntegrationTestCase):