Replace index with constraint

#700

db/migrate/20180212152810_add_epp_sessions_session_id_unique_constraint.rb

@@ -0,0 +1,13 @@
+class AddEppSessionsSessionIdUniqueConstraint < ActiveRecord::Migration
+  def up
+    execute <<-SQL
+      ALTER TABLE epp_sessions ADD CONSTRAINT unique_session_id UNIQUE (session_id)
+    SQL
+  end
+
+  def down
+    execute <<-SQL
+      ALTER TABLE epp_sessions DROP CONSTRAINT unique_session_id
+    SQL
+  end
+end

db/migrate/20180212154731_remove_epp_sessions_session_id_unique_index.rb

@@ -0,0 +1,5 @@
+class RemoveEppSessionsSessionIdUniqueIndex < ActiveRecord::Migration
+  def change
+    remove_index :epp_sessions, name: :index_epp_sessions_on_session_id
+  end
+end

db/structure.sql

@@ -3634,6 +3634,14 @@ ALTER TABLE ONLY contacts
     ADD CONSTRAINT unique_contact_code UNIQUE (code);
 
 
+--
+-- Name: unique_session_id; Type: CONSTRAINT; Schema: public; Owner: -; Tablespace: 
+--
+
+ALTER TABLE ONLY epp_sessions
+    ADD CONSTRAINT unique_session_id UNIQUE (session_id);
+
+
 --
 -- Name: unique_zone_origin; Type: CONSTRAINT; Schema: public; Owner: -; Tablespace: 
 --
@@ -3885,13 +3893,6 @@ CREATE INDEX index_domains_on_registrar_id ON domains USING btree (registrar_id)
 CREATE INDEX index_domains_on_statuses ON domains USING gin (statuses);
 
 
---
--- Name: index_epp_sessions_on_session_id; Type: INDEX; Schema: public; Owner: -; Tablespace: 
---
-
-CREATE UNIQUE INDEX index_epp_sessions_on_session_id ON epp_sessions USING btree (session_id);
-
-
 --
 -- Name: index_epp_sessions_on_updated_at; Type: INDEX; Schema: public; Owner: -; Tablespace: 
 --
@@ -5087,3 +5088,7 @@ INSERT INTO schema_migrations (version) VALUES ('20180207072139');
 
 INSERT INTO schema_migrations (version) VALUES ('20180212123810');
 
+INSERT INTO schema_migrations (version) VALUES ('20180212152810');
+
+INSERT INTO schema_migrations (version) VALUES ('20180212154731');
+