chi_clickhouse_metric_DetachedParts does not report zero

[filimonov]

missing metric instead

[Slach]

current query for fetch metric

		SELECT
			count() AS detached_parts,
			database,
			table,
			disk,
			if(coalesce(reason,'unknown')='','detached_by_user',coalesce(reason,'unknown')) AS detach_reason
		FROM system.detached_parts
		GROUP BY
			database,
			table,
			disk,
			reason

do you propose use system.tables LEFT JOIN system.detached_parts?

[Slach]

why do you need zero metric value?

[filimonov]

OK, probably that does not make too much sense, we just need to look on some other metric.

In short the problem is that it's hard to distinguish if the metric disappeared because it get zeroed, or because the scaping failed, and things like 'min_over_time' and similar work in a bit confusing way when the metric appears for a short a period of time, and then disappears again.