refactor(postgres): port Budget Variance report query to the query builder

The raw get_fiscal_years query had no ORDER BY (de-facto oldest-first); the
get_all port adds explicit order_by="name asc" so the Fiscal Year doctype
default (name DESC) does not reverse the report column order / cumulative values.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

erpnext/accounts/report/budget_variance_report/budget_variance_report.py

@@ -3,7 +3,7 @@
 
 import frappe
 from frappe import _
-from frappe.query_builder import CustomFunction
+from frappe.query_builder.custom import MonthName
 from frappe.utils import add_months, flt, formatdate
 
 from erpnext.accounts.doctype.accounting_dimension.accounting_dimension import get_dimensions
@@ -113,7 +113,6 @@ def build_budget_map(budget_records, filters):
 
 def get_actual_transactions(dimension_name, filters):
 	budget_against = frappe.scrub(filters.get("budget_against"))
-	monthname = CustomFunction("MONTHNAME", ["date"])
 
 	gle = frappe.qb.DocType("GL Entry")
 	budget = frappe.qb.DocType("Budget")
@@ -126,7 +125,7 @@ def get_actual_transactions(dimension_name, filters):
 			gle.debit,
 			gle.credit,
 			gle.fiscal_year,
-			monthname(gle.posting_date).as_("month_name"),
+			MonthName(gle.posting_date).as_("month_name"),
 			budget[budget_against].as_("budget_against"),
 		)
 		.where(
@@ -137,7 +136,10 @@ def get_actual_transactions(dimension_name, filters):
 			& (gle.is_cancelled == 0)
 			& (budget[budget_against] == dimension_name)
 		)
-		.groupby(gle.name)
+		# budget[budget_against] is selected from the Budget table, which is not functionally
+		# dependent on the grouped GL Entry PK, so postgres requires it in the GROUP BY. The WHERE
+		# pins it to dimension_name (a constant), so grouping by it does not change the result.
+		.groupby(gle.name, budget[budget_against])
 		.orderby(gle.fiscal_year)
 	)
 
@@ -157,15 +159,11 @@ def get_actual_transactions(dimension_name, filters):
 
 
 def get_budget_distributions(budget):
-	return frappe.db.sql(
-		"""
-			SELECT start_date, end_date, amount, percent
-			FROM `tabBudget Distribution`
-			WHERE parent = %s
-			ORDER BY start_date ASC
-		  """,
-		(budget.name,),
-		as_dict=True,
+	return frappe.get_all(
+		"Budget Distribution",
+		filters={"parent": budget.name},
+		fields=["start_date", "end_date", "amount", "percent"],
+		order_by="start_date asc",
 	)
 
 
@@ -351,20 +349,16 @@ def get_columns(filters):
 
 
 def get_fiscal_years(filters):
-	fiscal_year = frappe.db.sql(
-		"""
-			select
-				name
-			from
-				`tabFiscal Year`
-			where
-				name between %(from_fiscal_year)s and %(to_fiscal_year)s
-		""",
-		{"from_fiscal_year": filters["from_fiscal_year"], "to_fiscal_year": filters["to_fiscal_year"]},
+	return frappe.get_all(
+		"Fiscal Year",
+		filters={"name": ["between", [filters["from_fiscal_year"], filters["to_fiscal_year"]]]},
+		fields=["name"],
+		# the raw query had no ORDER BY (de-facto oldest-first); get_all would otherwise apply the
+		# Fiscal Year doctype default (name DESC) and reverse column order / cumulative-mode values.
+		order_by="name asc",
+		as_list=True,
 	)
 
-	return fiscal_year
-
 
 def get_cost_center_with_children(cost_centers):
 	"""Expand each cost center to include itself and all its descendants."""

erpnext/accounts/report/budget_variance_report/test_budget_variance_report.py

@@ -0,0 +1,27 @@
+# Copyright (c) 2024, Frappe Technologies Pvt. Ltd. and contributors
+# For license information, please see license.txt
+
+import frappe
+
+from erpnext.accounts.report.budget_variance_report.budget_variance_report import execute
+from erpnext.tests.utils import ERPNextTestSuite
+
+
+class TestBudgetVarianceReport(ERPNextTestSuite):
+	def test_report_executes(self):
+		# Smoke-guards the raw-SQL -> query-builder port: the report query must compile and run on
+		# both MariaDB and postgres.
+		company = frappe.db.get_value("Company", {}, "name")
+		fy = frappe.db.get_value("Fiscal Year", {}, "name", order_by="year_start_date desc")
+		columns, *_rest = execute(
+			frappe._dict(
+				{
+					"company": company,
+					"from_fiscal_year": fy,
+					"to_fiscal_year": fy,
+					"period": "Yearly",
+					"budget_against": "Cost Center",
+				}
+			)
+		)
+		self.assertTrue(columns)