promql

Documentation

Index

• func UnescapeLabelName(ln string) string
• type Transpiler
  • func (t *Transpiler) Transpile(expr promql.Expr) (*ast.File, error)

Functions

func UnescapeLabelName

func UnescapeLabelName(ln string) string

Types

type Transpiler

type Transpiler struct {
	Bucket     string
	Start      time.Time
	End        time.Time
	Resolution time.Duration
}

A Transpiler allows transpiling a PromQL expression into a Flux file according to a chosen evaluation time range.

func (*Transpiler) Transpile

func (t *Transpiler) Transpile(expr promql.Expr) (*ast.File, error)

Transpile converts a PromQL expression with the time ranges set in the transpiler into a Flux file. The resulting Flux file can be executed and the result needs to be transformed using FluxResultToPromQLValue() (implemented in the InfluxDB repo) to get a result value that is fully equivalent to the result of a native PromQL execution.

During the transpilation, the transpiler recursively translates the PromQL AST into equivalent Flux nodes. Each PromQL node translates into one or more Flux constructs that as a group (corresponding to the PromQL node) have to keep the following invariants:

• The "_field" column contains the PromQL metric name, if any.
• The "_measurement" column is ignored (always set to constant "prometheus").
• The "_time" column contains the sample timestamp as long as a raw sample has been selected from storage and not processed further. Otherwise, "_time" will be empty.
• The "_stop" column contains the stop timestamp of windows that are equivalent to the resolution steps in PromQL. If "_time" is no longer present, "_stop" becomes the output timestamp for a sample.
• The "_value" column is always of float type and represents the PromQL sample value.
• Other columns map to PromQL label names, with escaping applied ("_foo" -> "~_foo").
• Tables should be grouped by all columns except for "_time" and "_value". Each Flux table represents one PromQL series, with potentially multiple samples over time.