perf: Drop unused/duplicate/sub-optimal indexes (#38884)

* ci: enable more checks

* perf: Drop unused/duplicate indexes

erpnext/tests/test_perf.py

@@ -0,0 +1,24 @@
+import frappe
+from frappe.tests.utils import FrappeTestCase
+
+INDEXED_FIELDS = {
+	"Bin": ["item_code"],
+	"GL Entry": ["voucher_type", "against_voucher_type"],
+	"Purchase Order Item": ["item_code"],
+	"Stock Ledger Entry": ["warehouse"],
+}
+
+
+class TestPerformance(FrappeTestCase):
+	def test_ensure_indexes(self):
+		# These fields are not explicitly indexed BUT they are prefix in some
+		# other composite index. If those are removed this test should be
+		# updated accordingly.
+		for doctype, fields in INDEXED_FIELDS.items():
+			for field in fields:
+				self.assertTrue(
+					frappe.db.sql(
+						f"""SHOW INDEX FROM `tab{doctype}`
+						WHERE Column_name = "{field}" AND Seq_in_index = 1"""
+					)
+				)