refactor: get_group_by_count

Refactored raw query and partial get_all building with db.query + qb
notation equivalent. Added type hints & f-strings.

Intent: This particular API (for field "assigned_to") was taking
a while to run so decided to refactor this in hopes of perf improvemnts.

Result: 50% reduction in response times :D

frappe/desk/listview.py

@@ -1,6 +1,11 @@
-# Copyright (c) 2019, Frappe Technologies Pvt. Ltd. and Contributors
+# Copyright (c) 2022, Frappe Technologies Pvt. Ltd. and Contributors
 # License: MIT. See LICENSE
+from typing import Dict, List
+
 import frappe
+from frappe.query_builder.functions import Count
+from frappe.query_builder.terms import subqry
+from frappe.query_builder.utils import DocType
 
 
 @frappe.whitelist()
@@ -24,37 +29,36 @@ def set_list_settings(doctype, values):
 
 
 @frappe.whitelist()
-def get_group_by_count(doctype, current_filters, field):
+def get_group_by_count(doctype: str, current_filters: str, field: str) -> List[Dict]:
 	current_filters = frappe.parse_json(current_filters)
-	subquery_condition = ""
 
-	subquery = frappe.get_all(doctype, filters=current_filters, run=False)
 	if field == "assigned_to":
-		subquery_condition = " and `tabToDo`.reference_name in ({subquery})".format(subquery=subquery)
-		return frappe.db.sql(
-			"""select `tabToDo`.allocated_to as name, count(*) as count
-			from
-				`tabToDo`, `tabUser`
-			where
-				`tabToDo`.status!='Cancelled' and
-				`tabToDo`.allocated_to = `tabUser`.name and
-				`tabUser`.user_type = 'System User'
-				{subquery_condition}
-			group by
-				`tabToDo`.allocated_to
-			order by
-				count desc
-			limit 50""".format(
-				subquery_condition=subquery_condition
-			),
-			as_dict=True,
-		)
-	else:
-		return frappe.db.get_list(
-			doctype,
-			filters=current_filters,
-			group_by="`tab{0}`.{1}".format(doctype, field),
-			fields=["count(*) as count", "`{}` as name".format(field)],
-			order_by="count desc",
-			limit=50,
+		ToDo = DocType("ToDo")
+		User = DocType("User")
+		count = Count("*").as_("count")
+		filtered_records = frappe.db.query.build_conditions(doctype, current_filters).select("name")
+
+		return (
+			frappe.qb.from_(ToDo)
+			.from_(User)
+			.select(ToDo.allocated_to.as_("name"), count)
+			.where(
+				(ToDo.status != "Cancelled")
+				& (ToDo.allocated_to == User.name)
+				& (User.user_type == "System User")
+				& (ToDo.reference_name.isin(subqry(filtered_records)))
+			)
+			.groupby(ToDo.allocated_to)
+			.orderby(count)
+			.limit(50)
+			.run(as_dict=True)
 		)
+
+	return frappe.get_list(
+		doctype,
+		filters=current_filters,
+		group_by=f"`tab{doctype}`.{field}",
+		fields=["count(*) as count", f"`{field}` as name"],
+		order_by="count desc",
+		limit=50,
+	)