Set up foreign keys

migration/foreign_keys.6.cr

@@ -0,0 +1,85 @@
+class ForeignKeys < MG::Base
+  def up : String
+    <<-SQL
+    -- add foreign key to tags
+    ALTER TABLE tags RENAME TO tmp;
+
+    CREATE TABLE tags (
+      id TEXT NOT NULL,
+      tag TEXT NOT NULL,
+      UNIQUE (id, tag),
+      FOREIGN KEY (id) REFERENCES titles (id)
+        ON UPDATE CASCADE
+        ON DELETE CASCADE
+    );
+
+    INSERT INTO tags
+    SELECT * FROM tmp;
+
+    DROP TABLE tmp;
+
+    CREATE INDEX tags_id_idx ON tags (id);
+    CREATE INDEX tags_tag_idx ON tags (tag);
+
+    -- add foreign key to thumbnails
+    ALTER TABLE thumbnails RENAME TO tmp;
+
+    CREATE TABLE thumbnails (
+      id TEXT NOT NULL,
+      data BLOB NOT NULL,
+      filename TEXT NOT NULL,
+      mime TEXT NOT NULL,
+      size INTEGER NOT NULL,
+      FOREIGN KEY (id) REFERENCES ids (id)
+        ON UPDATE CASCADE
+        ON DELETE CASCADE
+    );
+
+    INSERT INTO thumbnails
+    SELECT * FROM tmp;
+
+    DROP TABLE tmp;
+
+    CREATE UNIQUE INDEX tn_index ON thumbnails (id);
+    SQL
+  end
+
+  def down : String
+    <<-SQL
+    -- remove foreign key from thumbnails
+    ALTER TABLE thumbnails RENAME TO tmp;
+
+    CREATE TABLE thumbnails (
+      id TEXT NOT NULL,
+      data BLOB NOT NULL,
+      filename TEXT NOT NULL,
+      mime TEXT NOT NULL,
+      size INTEGER NOT NULL
+    );
+
+    INSERT INTO thumbnails
+    SELECT * FROM tmp;
+
+    DROP TABLE tmp;
+
+    CREATE UNIQUE INDEX tn_index ON thumbnails (id);
+
+    -- remove foreign key from tags
+    ALTER TABLE tags RENAME TO tmp;
+
+    CREATE TABLE tags (
+      id TEXT NOT NULL,
+      tag TEXT NOT NULL,
+      UNIQUE (id, tag)
+    );
+
+    INSERT INTO tags
+    SELECT * FROM tmp;
+
+    DROP TABLE tmp;
+
+    CREATE INDEX tags_id_idx ON tags (id);
+    CREATE INDEX tags_tag_idx ON tags (tag);
+    SQL
+  end
+end