Add support for UNLOGGED Postgresql tables

This commit adds support for the
`ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.create_unlogged_tables`
setting, which turns `CREATE TABLE` SQL statements into
`CREATE UNLOGGED TABLE` statements.

This can improve PostgreSQL performance but at the
cost of data durability, and thus it is highly recommended
that you *DO NOT* enable this in a production environment.

1 files changed, 74 insertions, 0 deletions

diff --git a/activerecord/test/cases/adapters/postgresql/create_unlogged_tables_test.rb b/activerecord/test/cases/adapters/postgresql/create_unlogged_tables_test.rb
new file mode 100644
index 0000000000..a02bae1453
--- /dev/null
+++ b/activerecord/test/cases/adapters/postgresql/create_unlogged_tables_test.rb
@@ -0,0 +1,74 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "support/schema_dumping_helper"
+
+class UnloggedTablesTest < ActiveRecord::PostgreSQLTestCase
+  include SchemaDumpingHelper
+
+  TABLE_NAME = "things"
+  LOGGED_FIELD = "relpersistence"
+  LOGGED_QUERY = "SELECT #{LOGGED_FIELD} FROM pg_class WHERE relname = '#{TABLE_NAME}'"
+  LOGGED = "p"
+  UNLOGGED = "u"
+  TEMPORARY = "t"
+
+  class Thing < ActiveRecord::Base
+    self.table_name = TABLE_NAME
+  end
+
+  def setup
+    @connection = ActiveRecord::Base.connection
+    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.create_unlogged_tables = false
+  end
+
+  teardown do
+    @connection.drop_table TABLE_NAME, if_exists: true
+    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.create_unlogged_tables = false
+  end
+
+  def test_logged_by_default
+    @connection.create_table(TABLE_NAME) do |t|
+    end
+    assert_equal @connection.execute(LOGGED_QUERY).first[LOGGED_FIELD], LOGGED
+  end
+
+  def test_unlogged_in_test_environment_when_unlogged_setting_enabled
+    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.create_unlogged_tables = true
+
+    @connection.create_table(TABLE_NAME) do |t|
+    end
+    assert_equal @connection.execute(LOGGED_QUERY).first[LOGGED_FIELD], UNLOGGED
+  end
+
+  def test_not_included_in_schema_dump
+    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.create_unlogged_tables = true
+
+    @connection.create_table(TABLE_NAME) do |t|
+    end
+    assert_no_match(/unlogged/i, dump_table_schema(TABLE_NAME))
+  end
+
+  def test_not_changed_in_change_table
+    @connection.create_table(TABLE_NAME) do |t|
+    end
+
+    ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.create_unlogged_tables = true
+
+    @connection.change_table(TABLE_NAME) do |t|
+      t.column :name, :string
+    end
+    assert_equal @connection.execute(LOGGED_QUERY).first[LOGGED_FIELD], LOGGED
+  end
+
+  def test_gracefully_handles_temporary_tables
+    @connection.create_table(TABLE_NAME, temporary: true) do |t|
+    end
+
+    # Temporary tables are already unlogged, though this query results in a
+    # different result ("t" vs. "u"). This test is really just checking that we
+    # didn't try to run `CREATE TEMPORARY UNLOGGED TABLE`, which would result in
+    # a PostgreSQL error.
+    assert_equal @connection.execute(LOGGED_QUERY).first[LOGGED_FIELD], TEMPORARY
+  end
+end