Store: the series limit should count the number of unique series across the different blocks

[damnever]

Thanos, Prometheus and Golang version used:

Main Branch

Anything else we need to know:

The current series limit simply takes the sum of matched postings counts from blocks. Maybe we should count unique series for a better user experience

Thanos implementaion:

thanos/pkg/store/bucket.go

Lines 1179 to 1182 in 4a84785

	// Apply series limiter eargerly if lazy postings not enabled.
	if err := seriesLimiter.Reserve(uint64(len(b.lazyPostings.postings))); err != nil {
	return httpgrpc.Errorf(int(codes.ResourceExhausted), "exceeded series limit: %s", err)
	}

Cortex implementation:

https://github.com/cortexproject/cortex/blob/bb59466bcc2e4967c6b245407c539512e009e066/pkg/util/limiter/query_limiter.go#L69-L90

[yeya24]

+1 to the proposal. The implementation doesn't look like too hard but need proper benchmark to understand the performance impact.