perf: use LEFT JOIN instead of NOT EXISTS (backport #36221) (#36384)

* perf: use `LEFT JOIN` instead of `NOT EXISTS`

(cherry picked from commit 58d8675)

# Conflicts:
#	erpnext/manufacturing/doctype/bom_update_log/bom_updation_utils.py

* fix: long queue `process_boms_cost_level_wise`

(cherry picked from commit 148d466)

* chore: `conflicts`

* fix: failing test case

---------

Co-authored-by: s-aga-r <sagarsharma.s312@gmail.com>

erpnext/manufacturing/doctype/bom_update_log/bom_update_log.py

@@ -79,6 +79,7 @@ def on_submit(self):
 		else:
 			frappe.enqueue(
 				method="erpnext.manufacturing.doctype.bom_update_log.bom_update_log.process_boms_cost_level_wise",
+				queue="long",
 				update_doc=self,
 				now=frappe.flags.in_test,
 			)

erpnext/manufacturing/doctype/bom_update_log/bom_updation_utils.py

@@ -157,12 +157,21 @@ def _all_children_are_processed(parent_bom):
 def get_leaf_boms() -> List[str]:
 	"Get BOMs that have no dependencies."
 
-	return frappe.db.sql_list(
-		"""select name from `tabBOM` bom
-		where docstatus=1 and is_active=1
-			and not exists(select bom_no from `tabBOM Item`
-				where parent=bom.name and ifnull(bom_no, '')!='')"""
-	)
+	bom = frappe.qb.DocType("BOM")
+	bom_item = frappe.qb.DocType("BOM Item")
+
+	boms = (
+		frappe.qb.from_(bom)
+		.left_join(bom_item)
+		.on((bom.name == bom_item.parent) & (bom_item.bom_no != ""))
+		.select(bom.name)
+		.where((bom.docstatus == 1) & (bom.is_active == 1) & (bom_item.bom_no.isnull()))
+		.distinct()
+	).run(as_list=True)
+
+	boms = [bom[0] for bom in boms]
+
+	return boms
 
 
 def _generate_dependence_map() -> defaultdict: