Drop full index on ci_builds.token

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/333812

Changelog: performance

db/post_migrate/20210629104933_drop_index_on_ci_builds_for_token.rb

+# frozen_string_literal: true
+
+class DropIndexOnCiBuildsForToken < ActiveRecord::Migration[6.1]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  INDEXNAME = :index_ci_builds_on_token
+
+  def up
+    remove_concurrent_index_by_name :ci_builds, INDEXNAME
+  end
+
+  def down
+    add_concurrent_index :ci_builds, :token, unique: true, name: INDEXNAME
+  end
+end

db/schema_migrations/20210629104933

+2ec44dfd0745fd155ab3ab52153688a8969641134a9cc0cc485dd698cc8fd2d1
\ No newline at end of file

db/structure.sql

@@ -22800,8 +22800,6 @@ CREATE INDEX index_ci_builds_on_stage_id ON ci_builds USING btree (stage_id);
 
 CREATE INDEX index_ci_builds_on_status_and_type_and_runner_id ON ci_builds USING btree (status, type, runner_id);
 
-CREATE UNIQUE INDEX index_ci_builds_on_token ON ci_builds USING btree (token);
-
 CREATE UNIQUE INDEX index_ci_builds_on_token_encrypted ON ci_builds USING btree (token_encrypted) WHERE (token_encrypted IS NOT NULL);
 
 CREATE UNIQUE INDEX index_ci_builds_on_token_partial ON ci_builds USING btree (token) WHERE (token IS NOT NULL);