Metrics from 'gitlab_monitor_database' prometheus job parsing error

Version

GitLab CE 11.11.8

Description

Target for prometheus job gitlab_monitor_database returns a few invalid metrics. Promtool check returns this error:

$ curl -s http://localhost:9168/database|./promtool check metrics
error while linting: text format parsing error in line 303: expected float as value, got ""
(23) Failed writing body

These lines should be fixed:

gitlab_database_stat_table_idx_tup_fetch{table_name="tmp_ci_group_variables"}
gitlab_database_stat_table_idx_tup_fetch{table_name="tmp_ci_variables"}

On prometheus /targets page it looks like this:

Prometheus job config:

- job_name: gitlab_monitor_database
  metrics_path: "/database"
  static_configs:
  - targets:
    - localhost:9168

Possible fixes

Set '0' as initial value for aforementioned metrics.