From 6005fadacaccd27386a7e01d6acc850d6b3bda20 Mon Sep 17 00:00:00 2001
From: Krzysztof Kotlarek <kotlarek.krzysztof@gmail.com>
Date: Fri, 29 Nov 2019 12:41:42 +1100
Subject: [PATCH] FIX: add a unique index to developers table (#8436)

---
 ...28222140_add_unique_index_to_developers.rb | 24 +++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 db/migrate/20191128222140_add_unique_index_to_developers.rb

diff --git a/db/migrate/20191128222140_add_unique_index_to_developers.rb b/db/migrate/20191128222140_add_unique_index_to_developers.rb
new file mode 100644
index 00000000000..d839b157709
--- /dev/null
+++ b/db/migrate/20191128222140_add_unique_index_to_developers.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+class AddUniqueIndexToDevelopers < ActiveRecord::Migration[6.0]
+  def up
+    execute <<~SQL
+      DELETE FROM developers d1
+      USING (
+        SELECT MAX(id) as id, user_id
+        FROM developers
+        GROUP BY user_id
+        HAVING COUNT(*) > 1
+      ) d2
+      WHERE
+        d1.user_id = d2.user_id AND
+        d1.id <> d2.id
+    SQL
+
+    add_index :developers, %i(user_id), unique: true
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+end