Assert outside of transaction scope where possible

Using with_lock_retries outside of an existing transaction scope is safe
because it doesn't require us opening a subtransaction. Hence add
assertions to make sure we're outside of a transaction scope.

lib/gitlab/database/partitioning_migration_helpers/foreign_key_helpers.rb

@@ -6,6 +6,8 @@ module Gitlab
       module ForeignKeyHelpers
         include ::Gitlab::Database::SchemaHelpers
 
+        ERROR_SCOPE = 'foreign keys'
+
         # Adds a foreign key with only minimal locking on the tables involved.
         #
         # In concept it works similarly to add_concurrent_foreign_key, but we have
@@ -32,6 +34,8 @@ module Gitlab
         # name - The name of the foreign key.
         #
         def add_concurrent_partitioned_foreign_key(source, target, column:, on_delete: :cascade, name: nil)
+          assert_not_in_transaction_block(scope: ERROR_SCOPE)
+
           partition_options = {
             column: column,
             on_delete: on_delete,

lib/gitlab/database/partitioning_migration_helpers/index_helpers.rb

@@ -7,6 +7,8 @@ module Gitlab
         include Gitlab::Database::MigrationHelpers
         include Gitlab::Database::SchemaHelpers
 
+        ERROR_SCOPE = 'index'
+
         # Concurrently creates a new index on a partitioned table. In concept this works similarly to
         # `add_concurrent_index`, and won't block reads or writes on the table while the index is being built.
         #
@@ -21,6 +23,8 @@ module Gitlab
         #
         # See Rails' `add_index` for more info on the available arguments.
         def add_concurrent_partitioned_index(table_name, column_names, options = {})
+          assert_not_in_transaction_block(scope: ERROR_SCOPE)
+
           raise ArgumentError, 'A name is required for indexes added to partitioned tables' unless options[:name]
 
           partitioned_table = find_partitioned_table(table_name)
@@ -57,6 +61,8 @@ module Gitlab
         #
         #     remove_concurrent_partitioned_index_by_name :users, 'index_name_goes_here'
         def remove_concurrent_partitioned_index_by_name(table_name, index_name)
+          assert_not_in_transaction_block(scope: ERROR_SCOPE)
+
           find_partitioned_table(table_name)
 
           unless index_name_exists?(table_name, index_name)

spec/lib/gitlab/database/partitioning_migration_helpers/foreign_key_helpers_spec.rb

@@ -27,6 +27,7 @@ RSpec.describe Gitlab::Database::PartitioningMigrationHelpers::ForeignKeyHelpers
 
   before do
     allow(migration).to receive(:puts)
+    allow(migration).to receive(:transaction_open?).and_return(false)
 
     connection.execute(<<~SQL)
       CREATE TABLE #{target_table_name} (
@@ -141,5 +142,15 @@ RSpec.describe Gitlab::Database::PartitioningMigrationHelpers::ForeignKeyHelpers
           .with(source_table_name, target_table_name, options)
       end
     end
+
+    context 'when run inside a transaction block' do
+      it 'raises an error' do
+        expect(migration).to receive(:transaction_open?).and_return(true)
+
+        expect do
+          migration.add_concurrent_partitioned_foreign_key(source_table_name, target_table_name, column: column_name)
+        end.to raise_error(/can not be run inside a transaction/)
+      end
+    end
   end
 end

spec/lib/gitlab/database/partitioning_migration_helpers/index_helpers_spec.rb

@@ -20,6 +20,7 @@ RSpec.describe Gitlab::Database::PartitioningMigrationHelpers::IndexHelpers do
 
   before do
     allow(migration).to receive(:puts)
+    allow(migration).to receive(:transaction_open?).and_return(false)
 
     connection.execute(<<~SQL)
       CREATE TABLE #{table_name} (
@@ -127,6 +128,16 @@ RSpec.describe Gitlab::Database::PartitioningMigrationHelpers::IndexHelpers do
         end.to raise_error(ArgumentError, /#{table_name} is not a partitioned table/)
       end
     end
+
+    context 'when run inside a transaction block' do
+      it 'raises an error' do
+        expect(migration).to receive(:transaction_open?).and_return(true)
+
+        expect do
+          migration.add_concurrent_partitioned_index(table_name, column_name)
+        end.to raise_error(/can not be run inside a transaction/)
+      end
+    end
   end
 
   describe '#remove_concurrent_partitioned_index_by_name' do
@@ -182,5 +193,15 @@ RSpec.describe Gitlab::Database::PartitioningMigrationHelpers::IndexHelpers do
         end.to raise_error(ArgumentError, /#{table_name} is not a partitioned table/)
       end
     end
+
+    context 'when run inside a transaction block' do
+      it 'raises an error' do
+        expect(migration).to receive(:transaction_open?).and_return(true)
+
+        expect do
+          migration.remove_concurrent_partitioned_index_by_name(table_name, index_name)
+        end.to raise_error(/can not be run inside a transaction/)
+      end
+    end
   end
 end