Hash concurrent foreign key names similar to Rails

This was initially not implemented simply because I forgot about the
size limit of constraint names in PostgreSQL (63 bytes). Using the old
technique we can't add foreign keys for certain tables. For example,
adding a foreign key on
protected_branch_merge_access_levels.protected_branch_id would lead to
the following key name:

    fk_protected_branch_merge_access_levels_protected_branches_protected_branch_id

This key is 78 bytes long, thus violating the PostgreSQL size
requirements.

The hashing strategy is copied from Rails' foreign_key_name() method,
which unfortunately is private and subject to change without notice.

1 files changed, 10 insertions, 0 deletions

diff --git a/spec/lib/gitlab/database/migration_helpers_spec.rb b/spec/lib/gitlab/database/migration_helpers_spec.rb
index e94ca4fcfd2..e007044868c 100644
--- a/spec/lib/gitlab/database/migration_helpers_spec.rb
+++ b/spec/lib/gitlab/database/migration_helpers_spec.rb
@@ -101,6 +101,16 @@ describe Gitlab::Database::MigrationHelpers, lib: true do
     end
   end
 
+  describe '#concurrent_foreign_key_name' do
+    it 'returns the name for a foreign key' do
+      name = model.concurrent_foreign_key_name(:this_is_a_very_long_table_name,
+                                               :with_a_very_long_column_name)
+
+      expect(name).to be_an_instance_of(String)
+      expect(name.length).to eq(13)
+    end
+  end
+
   describe '#disable_statement_timeout' do
     context 'using PostgreSQL' do
       it 'disables statement timeouts' do