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chore(promql): add public API to be able to evaluate duration expressions

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Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>
This commit is contained in:
György Krajcsovits 2025-07-10 13:05:18 +02:00
parent 0672a5b045
commit caff76d86b
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GPG Key ID: 47A8F9CE80FD7C7F
3 changed files with 16 additions and 8 deletions
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18
promql/durations.go
View File

@ -21,12 +21,20 @@ import (
"github.com/prometheus/prometheus/promql/parser"
)
// durationVisitor is a visitor that visits a duration expression and calculates the duration.
type durationVisitor struct {
// DurationVisitor is a visitor that visits a duration expression and calculates the duration.
type DurationVisitor struct {
step time.Duration
}
func (v *durationVisitor) Visit(node parser.Node, _ []parser.Node) (parser.Visitor, error) {
// NewDurationVisitor creates a visitor to Walk and evaluate duration
// expressions in a parsed query.
func NewDurationVisitor(step time.Duration) *DurationVisitor {
return &DurationVisitor{
step: step,
}
}
func (v *DurationVisitor) Visit(node parser.Node, _ []parser.Node) (parser.Visitor, error) {
switch n := node.(type) {
case *parser.VectorSelector:
if n.OriginalOffsetExpr != nil {
@ -71,7 +79,7 @@ func (v *durationVisitor) Visit(node parser.Node, _ []parser.Node) (parser.Visit
}
// calculateDuration computes the duration from a duration expression.
func (v *durationVisitor) calculateDuration(expr parser.Expr, allowedNegative bool) (time.Duration, error) {
func (v *DurationVisitor) calculateDuration(expr parser.Expr, allowedNegative bool) (time.Duration, error) {
duration, err := v.evaluateDurationExpr(expr)
if err != nil {
return 0, err
@ -86,7 +94,7 @@ func (v *durationVisitor) calculateDuration(expr parser.Expr, allowedNegative bo
}
// evaluateDurationExpr recursively evaluates a duration expression to a float64 value.
func (v *durationVisitor) evaluateDurationExpr(expr parser.Expr) (float64, error) {
func (v *DurationVisitor) evaluateDurationExpr(expr parser.Expr) (float64, error) {
switch n := expr.(type) {
case *parser.NumberLiteral:
return n.Val, nil

4
promql/durations_test.go
View File

@ -41,7 +41,7 @@ func TestDurationVisitor(t *testing.T) {
expr, err := parser.ParseExpr(complexExpr)
require.NoError(t, err)
err = parser.Walk(&durationVisitor{}, expr, nil)
err = parser.Walk(NewDurationVisitor(0), expr, nil)
require.NoError(t, err)
// Verify different parts of the expression have correct durations.
@ -243,7 +243,7 @@ func TestCalculateDuration(t *testing.T) {
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
v := &durationVisitor{step: 1 * time.Second}
v := NewDurationVisitor(1 * time.Second)
result, err := v.calculateDuration(tt.expr, tt.allowedNegative)
if tt.errorMessage != "" {
require.Error(t, err)

2
promql/engine.go
View File

@ -3734,7 +3734,7 @@ func unwrapStepInvariantExpr(e parser.Expr) parser.Expr {
func PreprocessExpr(expr parser.Expr, start, end time.Time, step time.Duration) (parser.Expr, error) {
detectHistogramStatsDecoding(expr)
if err := parser.Walk(&durationVisitor{step: step}, expr, nil); err != nil {
if err := parser.Walk(NewDurationVisitor(step), expr, nil); err != nil {
return nil, err
}