From 2a496a0e082062600e813cd43eba8812fdc00f6d Mon Sep 17 00:00:00 2001
From: Keiran Price <keiran.price@stfc.ac.uk>
Date: Wed, 11 Sep 2019 09:46:16 +0100
Subject: [PATCH] #41: Add implementation to filter

---
 common/database_helpers.py | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/common/database_helpers.py b/common/database_helpers.py
index 303e6712..2c003111 100644
--- a/common/database_helpers.py
+++ b/common/database_helpers.py
@@ -152,8 +152,16 @@ def apply_filter(self, query):
 class DistinctFieldFilter(QueryFilter):
     precedence = 0
 
+    def __init__(self, fields):
+        self.fields = fields if type(fields) is list else [fields]  # This allows single string distinct filters
+
     def apply_filter(self, query):
-        pass
+        query.is_distinct_fields_query = True
+        try:
+            self.fields = [getattr(query.table, field) for field in self.fields]
+        except AttributeError:
+            raise BadFilterError("Bad field requested")
+        query.base_query = query.session.query(*self.fields).distinct()
 
 
 class OrderFilter(QueryFilter):