From ed688bec8c88d23111dc584ebe351578ac1578f4 Mon Sep 17 00:00:00 2001
From: David Taylor <david@taylorhq.com>
Date: Mon, 30 Aug 2021 12:31:22 +0100
Subject: [PATCH] FIX: Ensure id sequences are not reset during db:migrate
 (#14184)

The seed-fu gem resets the sequence on all the tables it touches. In some situations, this can cause primary keys to be re-used. This commit introduces a freedom patch which ensures seed-fu only touches the sequence when it is less than the id of one of the seeded records.
---
 lib/freedom_patches/seed_fu.rb                | 19 +++++++++++++++++++
 .../freedom_patches/seed_fu_spec.rb           | 19 +++++++++++++++++++
 2 files changed, 38 insertions(+)
 create mode 100644 lib/freedom_patches/seed_fu.rb
 create mode 100644 spec/components/freedom_patches/seed_fu_spec.rb

diff --git a/lib/freedom_patches/seed_fu.rb b/lib/freedom_patches/seed_fu.rb
new file mode 100644
index 00000000000..b24241b3d73
--- /dev/null
+++ b/lib/freedom_patches/seed_fu.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+SeedFu::Seeder.prepend(Module.new do
+  def update_id_sequence
+    max_seeded_id = @data.filter_map { |d| d["id"] }.max
+    seq = @model_class.connection.execute(<<~SQL)
+      SELECT last_value
+      FROM #{@model_class.sequence_name}
+    SQL
+    last_seq_value = seq.first["last_value"]
+
+    if max_seeded_id && last_seq_value < max_seeded_id
+      # Update the sequence to start from the highest existing id
+      @model_class.connection.reset_pk_sequence!(@model_class.table_name)
+    else
+      # The sequence is already higher than any of our seeded ids - better not touch it
+    end
+  end
+end)
diff --git a/spec/components/freedom_patches/seed_fu_spec.rb b/spec/components/freedom_patches/seed_fu_spec.rb
new file mode 100644
index 00000000000..3bb1876411a
--- /dev/null
+++ b/spec/components/freedom_patches/seed_fu_spec.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe "seed-fu patch" do
+  it "does not modify a sequence on an existing table" do
+    u = User.create!(username: "test1", email: "test1@example.com")
+    uid1 = u.id
+    UserDestroyer.new(Discourse.system_user).destroy(u)
+
+    SeedFu.quiet = true
+    SeedFu.seed
+
+    # Ensure sequence was not reset. A new user should have
+    # id one greater than the last user
+    u2 = User.create!(username: "test1", email: "test1@example.com")
+    expect(u2.id).to eq(uid1 + 1)
+  end
+end