From 005c5b830cfdb0526b754f9cf8bc44ffddc45d54 Mon Sep 17 00:00:00 2001
From: Sebastian Serth <Sebastian.Serth@hpi.de>
Date: Mon, 27 Jul 2020 17:45:19 +0200
Subject: [PATCH] Add function to merge exercises

Use with caution!
---
 db/scripts/migrate_exercise.sql | 88 +++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 db/scripts/migrate_exercise.sql

diff --git a/db/scripts/migrate_exercise.sql b/db/scripts/migrate_exercise.sql
new file mode 100644
index 00000000..0c16e5af
--- /dev/null
+++ b/db/scripts/migrate_exercise.sql
@@ -0,0 +1,88 @@
+CREATE OR REPLACE FUNCTION migrate_exercise(target_exercise int, duplicated_exercise int)
+    RETURNS VOID
+    LANGUAGE plpgsql
+AS
+$$
+DECLARE
+
+BEGIN
+    IF target_exercise = duplicated_exercise THEN
+        RETURN;
+    END IF;
+
+    UPDATE submissions SET exercise_id = target_exercise WHERE exercise_id = duplicated_exercise;
+    UPDATE request_for_comments SET exercise_id = target_exercise WHERE exercise_id = duplicated_exercise;
+
+    WITH rename_candidates AS (
+        SELECT target.name, target.id AS target_id, duplicated.id AS duplicated_id
+        FROM files AS target
+                 INNER JOIN files AS duplicated ON target.name = duplicated.name
+        WHERE target.context_id = target_exercise
+          AND target.context_type = 'Exercise'
+          AND target.read_only = FALSE
+          AND duplicated.context_id = duplicated_exercise
+          AND duplicated.context_type = 'Exercise'
+          AND duplicated.read_only = FALSE
+    ),
+         files_mapping AS (
+             SELECT files.id, rename_candidates.target_id
+             FROM files
+                      INNER JOIN rename_candidates ON file_id = duplicated_id)
+    UPDATE files
+    SET file_id = files_mapping.target_id
+    FROM files_mapping
+    WHERE files.id = files_mapping.id;
+
+    UPDATE events SET exercise_id = target_exercise where exercise_id = duplicated_exercise;
+    UPDATE searches SET exercise_id = target_exercise where exercise_id = duplicated_exercise;
+    UPDATE user_exercise_interventions SET exercise_id = target_exercise where exercise_id = duplicated_exercise;
+    UPDATE user_proxy_exercise_exercises SET exercise_id = target_exercise where exercise_id = duplicated_exercise;
+
+    DELETE FROM anomaly_notifications WHERE exercise_id = duplicated_exercise;
+    DELETE FROM exercise_tags WHERE exercise_id = duplicated_exercise;
+    DELETE FROM lti_parameters WHERE exercises_id = duplicated_exercise;
+    DELETE FROM remote_evaluation_mappings WHERE exercise_id = duplicated_exercise;
+
+    -- Preventing duplicated entries in exercise_collection_items
+    -- An exercise should not be present twice in an exercise collection.
+    DELETE
+    FROM exercise_collection_items
+    WHERE id IN (SELECT duplicated.id
+                 FROM exercise_collection_items AS target,
+                      exercise_collection_items AS duplicated
+                 WHERE target.exercise_id = target_exercise
+                   AND duplicated.exercise_id = duplicated_exercise
+                   AND target.exercise_collection_id = duplicated.exercise_collection_id);
+    UPDATE exercise_collection_items SET exercise_id = target_exercise where exercise_id = duplicated_exercise;
+
+    -- Preventing duplicated entries in exercises_proxy_exercises
+    -- The same proxy exercise should not have two entries for the same exercise it proxies.
+    DELETE
+    FROM exercises_proxy_exercises
+    WHERE exercise_id = duplicated_exercise
+      AND proxy_exercise_id IN (SELECT duplicated.proxy_exercise_id
+                                FROM exercises_proxy_exercises AS target,
+                                     exercises_proxy_exercises AS duplicated
+                                WHERE target.exercise_id = target_exercise
+                                  AND duplicated.exercise_id = duplicated_exercise
+                                  AND target.proxy_exercise_id = duplicated.proxy_exercise_id);
+    UPDATE exercises_proxy_exercises SET exercise_id = target_exercise where exercise_id = duplicated_exercise;
+
+    -- Preventing duplicated entries in user_exercise_feedbacks
+    -- An exercise should not have two feedbacks from the same user.
+    DELETE
+    FROM user_exercise_feedbacks
+    WHERE id IN (SELECT target.id
+                 FROM user_exercise_feedbacks AS target,
+                      user_exercise_feedbacks AS duplicated
+                 WHERE target.exercise_id = target_exercise
+                   AND duplicated.exercise_id = duplicated_exercise
+                   AND target.user_id = duplicated.user_id
+                   AND target.user_type = duplicated.user_type);
+    UPDATE user_exercise_feedbacks SET exercise_id = target_exercise where exercise_id = duplicated_exercise;
+
+    DELETE FROM files WHERE context_id = duplicated_exercise and context_type = 'Exercise';
+    DELETE FROM exercises WHERE id = duplicated_exercise;
+
+END;
+$$;