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Merge pull request #18263 from linasm/do-not-skip-buckets-if-trimming

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fix(PromQL): do not skip histogram buckets when trimming
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Bartlomiej Plotka 2026-03-10 12:37:57 +01:00 committed by GitHub
commit de56b4c528
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2 changed files with 32 additions and 20 deletions
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46
promql/engine.go
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@ -4393,31 +4393,37 @@ func detectHistogramStatsDecoding(expr parser.Expr) {
pathLoop:
for i := len(path) - 1; i >= 0; i-- { // Walk backwards up the path.
if _, ok := path[i].(*parser.SubqueryExpr); ok {
switch p := path[i].(type) {
case *parser.SubqueryExpr:
// If we ever see a subquery in the path, we
// will not skip the buckets. We need the
// buckets for correct counter reset detection.
n.SkipHistogramBuckets = false
break pathLoop
}
call, ok := path[i].(*parser.Call)
if !ok {
continue pathLoop
}
switch call.Func.Name {
case "histogram_count", "histogram_sum", "histogram_avg":
// We allow skipping buckets preliminarily. But
// we will continue through the path to see if
// we find a subquery (or a histogram function)
// further up (the latter wouldn't make sense,
// but no harm in detecting it).
n.SkipHistogramBuckets = true
case "histogram_quantile", "histogram_quantiles", "histogram_fraction":
// If we ever see a function that needs the
// whole histogram, we will not skip the
// buckets.
n.SkipHistogramBuckets = false
break pathLoop
case *parser.Call:
switch p.Func.Name {
case "histogram_count", "histogram_sum", "histogram_avg":
// We allow skipping buckets preliminarily. But
// we will continue through the path to see if
// we find a subquery (or a histogram function)
// further up (the latter wouldn't make sense,
// but no harm in detecting it).
n.SkipHistogramBuckets = true
case "histogram_quantile", "histogram_quantiles", "histogram_fraction":
// If we ever see a function that needs the
// whole histogram, we will not skip the
// buckets.
n.SkipHistogramBuckets = false
break pathLoop
}
case *parser.BinaryExpr:
if p.Op == parser.TRIM_UPPER || p.Op == parser.TRIM_LOWER {
// Trimming depends on buckets, we will not skip them.
n.SkipHistogramBuckets = false
break pathLoop
}
}
}
return nil

6
promql/promqltest/testdata/native_histograms.test vendored
View file

@ -2359,6 +2359,12 @@ eval instant at 1m cbh_two_buckets_split_at_negative >/ 0.0
eval instant at 1m cbh_two_buckets_split_at_negative >/ 10.0
cbh_two_buckets_split_at_negative {{schema:-53 sum:1000.0 count:100 custom_values:[-5] buckets:[0 100]}}
# Verify there is no interference from skip buckets optimization:
eval instant at 1m histogram_sum(cbh_two_buckets_split_at_negative >/ 10.0)
{} 1000
eval instant at 1m histogram_count(cbh_two_buckets_split_at_negative >/ 10.0)
{} 100
load 1m
cbh_for_join{label="a"} {{schema:-53 sum:33 count:101 custom_values:[5] buckets:[1 100]}}