[Cardinality API] Include missing labels in label values #8450
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When querying for cardinality by some label, the result may not add up to the total cardinality. This is because some series may be missing that label entirely. Instead, this change will include the empty value in the result. As an optimization, the empty value is skipped if it would be filtered out by matchers.
Co-authored-by: Mauro Stettler <[email protected]>
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| if emptyValueAllowedByMatchers { | ||
| lblValues = append(lblValues, "") |
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this would hugely increase the scope of the endpoint when requesting negative matchers (pod!="X"). So the ingester will have to also find all series without the pod label, which means taking the union of all the lists for all values of pod and subtract them from the list of postings for this call.
Is it an option to just subtract the sum of all label values from the number of all series that match the matchers and add this value to the result instead?
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| // Check if empty value for label is allowed according to matchers. This | ||
| // is an optimization only to avoid fetching postings, since the posting | ||
| // list would be empty anyway. | ||
| emptyValueAllowedByMatchers := true | ||
| for _, matcher := range matchers { | ||
| if matcher.Name != lblName { | ||
| continue | ||
| } | ||
| if !matcher.Matches("") { | ||
| emptyValueAllowedByMatchers = false | ||
| break | ||
| } | ||
| } | ||
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| if emptyValueAllowedByMatchers { | ||
| lblValues = append(lblValues, "") | ||
| } |
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nitpick if you can move this into a tiny function of its own because labelValuesCardinality is becoming long with time
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The CHANGELOG has just been cut to prepare for the next Mimir release. Please rebase |
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Thank you for your contribution. This pull request has been marked as stale because it has had no activity in the last 150 days. It will be closed in 30 days if there is no further activity. If you need more time, you can add a comment to the PR. |
What this PR does
When querying for cardinality by some label, the result may not add up to the total cardinality. This is because some series may be missing that label entirely. Instead, this change will include the empty value in the result. As an optimization, the empty value is skipped if it would be filtered out by matchers.
Which issue(s) this PR fixes or relates to
Reported as a nice-to-have for the cardinality dashboards, and it's a trivial change so why not 😃
Checklist
CHANGELOG.mdupdated - the order of entries should be[CHANGE],[FEATURE],[ENHANCEMENT],[BUGFIX].about-versioning.mdupdated with experimental features.