Merge pull request #421 from bookbrainz/delete-duplicate-relationships

BB-292 fix(sql): Script to delete duplicate relationships

sql/scripts/delete_duplicate_relationships.sql

@@ -0,0 +1,27 @@
+-- This script selects exact duplicate relationships that appear in the same relationshipSet
+-- then deletes them from the relevant tables
+
+CREATE TEMPORARY TABLE IF NOT EXISTS duplicate_relationship_ids
+as select distinct id from (
+	select
+	dupe.id
+	FROM relationship as dupe
+	join relationship_set__relationship as set1 on  set1.relationship_id = dupe.id
+	join relationship as keep on
+		 dupe.id > keep.id and dupe.type_id = keep.type_id and dupe.source_bbid = keep.source_bbid and dupe.target_bbid = keep.target_bbid
+	join relationship_set__relationship as set2 on  set2.relationship_id = keep.id
+	-- target only duplicate relationships that appear in the same set
+	where set1.set_id = set2.set_id
+) duplicate_relationships;
+
+BEGIN TRANSACTION;
+
+DELETE FROM relationship_set__relationship
+    USING duplicate_relationship_ids
+    WHERE relationship_set__relationship.relationship_id = duplicate_relationship_ids.id;
+
+DELETE FROM relationship
+    USING duplicate_relationship_ids
+    where relationship.id = duplicate_relationship_ids.id;
+
+COMMIT TRANSACTION;