loki/pkg/querier/queryrange/ingester_query_window.go

package queryrange

import (
	"time"

	"github.com/grafana/loki/v3/pkg/util"
	"github.com/grafana/loki/v3/pkg/util/validation"
)

// SplitIntervalForTimeRange returns the correct split interval to use. It accounts for the given upperBound value being
// within the ingester query window, in which case it returns the ingester query split (unless it's not set, then the default
// split interval will be used).
func SplitIntervalForTimeRange(iqo util.IngesterQueryOptions, limits Limits, defaultSplitFn func(string) time.Duration, tenantIDs []string, ref, upperBound time.Time) time.Duration {
	split := validation.SmallestPositiveNonZeroDurationPerTenant(tenantIDs, defaultSplitFn)

	if iqo == nil {
		return split
	}

	// if the query is within the ingester query window, choose the ingester split duration (if configured), otherwise
	// revert to the default split duration
	ingesterQueryWindowStart := ref.Add(-iqo.QueryIngestersWithin())

	// query is (even partially) within the ingester query window
	if upperBound.After(ingesterQueryWindowStart) {
		ingesterSplit := validation.MaxDurationOrZeroPerTenant(tenantIDs, limits.IngesterQuerySplitDuration)
		if !iqo.QueryStoreOnly() && ingesterSplit > 0 {
			split = ingesterSplit
		}
	}

	return split
}