diff --git a/frappe/database/mariadb/schema.py b/frappe/database/mariadb/schema.py
index f1691765b5..f7abac6547 100644
--- a/frappe/database/mariadb/schema.py
+++ b/frappe/database/mariadb/schema.py
@@ -69,7 +69,7 @@ class MariaDBTable(DBTable):
 				if unique_constraint_changed and not col.unique:
 					unique_index_record = frappe.db.sql("""
 						SHOW INDEX FROM `{0}`
-						WHERE Column_name=%s
+						WHERE Key_name=%s
 						AND Non_unique=0
 					""".format(self.table_name), (col.fieldname), as_dict=1)
 					if unique_index_record:
@@ -79,9 +79,9 @@ class MariaDBTable(DBTable):
 				if index_constraint_changed and not col.set_index:
 					index_record = frappe.db.sql("""
 						SHOW INDEX FROM `{0}`
-						WHERE Column_name=%s
+						WHERE Key_name=%s
 						AND Non_unique=1
-					""".format(self.table_name), (col.fieldname), as_dict=1)
+					""".format(self.table_name), (col.fieldname + '_index'), as_dict=1)
 					if index_record:
 						drop_index_query.append("DROP INDEX `{}`".format(index_record[0].Key_name))
 
diff --git a/frappe/database/schema.py b/frappe/database/schema.py
index 10582eff8f..5b4788a9c2 100644
--- a/frappe/database/schema.py
+++ b/frappe/database/schema.py
@@ -230,7 +230,7 @@ class DbColumn:
 			self.table.set_default.append(self)
 
 		# index should be applied or dropped irrespective of type change
-		if ((current_def['index'] and not self.set_index and not self.unique)
+		if ((current_def['index'] and not self.set_index)
 			or (current_def['unique'] and not self.unique)):
 			# to drop unique you have to drop index
 			self.table.drop_index.append(self)