prometheus/promql/ast.go

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// Copyright 2015 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package promql
import (
"fmt"
"time"
"github.com/prometheus/common/model"
"github.com/prometheus/prometheus/storage/local"
"github.com/prometheus/prometheus/storage/metric"
)
// Node is a generic interface for all nodes in an AST.
//
// Whenever numerous nodes are listed such as in a switch-case statement
// or a chain of function definitions (e.g. String(), expr(), etc.) convention is
// to list them as follows:
//
// - Statements
// - statement types (alphabetical)
// - ...
// - Expressions
// - expression types (alphabetical)
// - ...
//
type Node interface {
// String representation of the node that returns the given node when parsed
// as part of a valid query.
String() string
}
// Statement is a generic interface for all statements.
type Statement interface {
Node
// stmt ensures that no other type accidentally implements the interface
stmt()
}
// Statements is a list of statement nodes that implements Node.
type Statements []Statement
// AlertStmt represents an added alert rule.
type AlertStmt struct {
Name string
Expr Expr
Duration time.Duration
Labels model.LabelSet
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Annotations model.LabelSet
}
// EvalStmt holds an expression and information on the range it should
// be evaluated on.
type EvalStmt struct {
Expr Expr // Expression to be evaluated.
// The time boundaries for the evaluation. If Start equals End an instant
// is evaluated.
Start, End model.Time
// Time between two evaluated instants for the range [Start:End].
Interval time.Duration
}
// RecordStmt represents an added recording rule.
type RecordStmt struct {
Name string
Expr Expr
Labels model.LabelSet
}
func (*AlertStmt) stmt() {}
func (*EvalStmt) stmt() {}
func (*RecordStmt) stmt() {}
// Expr is a generic interface for all expression types.
type Expr interface {
Node
// Type returns the type the expression evaluates to. It does not perform
// in-depth checks as this is done at parsing-time.
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Type() model.ValueType
// expr ensures that no other types accidentally implement the interface.
expr()
}
// Expressions is a list of expression nodes that implements Node.
type Expressions []Expr
// AggregateExpr represents an aggregation operation on a vector.
type AggregateExpr struct {
Op itemType // The used aggregation operation.
Expr Expr // The vector expression over which is aggregated.
Grouping model.LabelNames // The labels by which to group the vector.
Without bool // Whether to drop the given labels rather than keep them.
KeepCommonLabels bool // Whether to keep common labels among result elements.
}
// BinaryExpr represents a binary expression between two child expressions.
type BinaryExpr struct {
Op itemType // The operation of the expression.
LHS, RHS Expr // The operands on the respective sides of the operator.
// The matching behavior for the operation if both operands are vectors.
// If they are not this field is nil.
VectorMatching *VectorMatching
// If a comparison operator, return 0/1 rather than filtering.
ReturnBool bool
}
// Call represents a function call.
type Call struct {
Func *Function // The function that was called.
Args Expressions // Arguments used in the call.
}
// MatrixSelector represents a matrix selection.
type MatrixSelector struct {
Name string
Range time.Duration
Offset time.Duration
LabelMatchers metric.LabelMatchers
// The series iterators are populated at query analysis time.
iterators map[model.Fingerprint]local.SeriesIterator
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metrics map[model.Fingerprint]metric.Metric
}
// NumberLiteral represents a number.
type NumberLiteral struct {
Val model.SampleValue
}
// ParenExpr wraps an expression so it cannot be disassembled as a consequence
// of operator precedence.
type ParenExpr struct {
Expr Expr
}
// StringLiteral represents a string.
type StringLiteral struct {
Val string
}
// UnaryExpr represents a unary operation on another expression.
// Currently unary operations are only supported for scalars.
type UnaryExpr struct {
Op itemType
Expr Expr
}
// VectorSelector represents a vector selection.
type VectorSelector struct {
Name string
Offset time.Duration
LabelMatchers metric.LabelMatchers
// The series iterators are populated at query analysis time.
iterators map[model.Fingerprint]local.SeriesIterator
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metrics map[model.Fingerprint]metric.Metric
}
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func (e *AggregateExpr) Type() model.ValueType { return model.ValVector }
func (e *Call) Type() model.ValueType { return e.Func.ReturnType }
func (e *MatrixSelector) Type() model.ValueType { return model.ValMatrix }
func (e *NumberLiteral) Type() model.ValueType { return model.ValScalar }
func (e *ParenExpr) Type() model.ValueType { return e.Expr.Type() }
func (e *StringLiteral) Type() model.ValueType { return model.ValString }
func (e *UnaryExpr) Type() model.ValueType { return e.Expr.Type() }
func (e *VectorSelector) Type() model.ValueType { return model.ValVector }
func (e *BinaryExpr) Type() model.ValueType {
if e.LHS.Type() == model.ValScalar && e.RHS.Type() == model.ValScalar {
return model.ValScalar
}
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return model.ValVector
}
func (*AggregateExpr) expr() {}
func (*BinaryExpr) expr() {}
func (*Call) expr() {}
func (*MatrixSelector) expr() {}
func (*NumberLiteral) expr() {}
func (*ParenExpr) expr() {}
func (*StringLiteral) expr() {}
func (*UnaryExpr) expr() {}
func (*VectorSelector) expr() {}
// VectorMatchCardinality describes the cardinality relationship
// of two vectors in a binary operation.
type VectorMatchCardinality int
const (
CardOneToOne VectorMatchCardinality = iota
CardManyToOne
CardOneToMany
CardManyToMany
)
func (vmc VectorMatchCardinality) String() string {
switch vmc {
case CardOneToOne:
return "one-to-one"
case CardManyToOne:
return "many-to-one"
case CardOneToMany:
return "one-to-many"
case CardManyToMany:
return "many-to-many"
}
panic("promql.VectorMatchCardinality.String: unknown match cardinality")
}
// VectorMatching describes how elements from two vectors in a binary
// operation are supposed to be matched.
type VectorMatching struct {
// The cardinality of the two vectors.
Card VectorMatchCardinality
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// MatchingLabels contains the labels which define equality of a pair of
// elements from the vectors.
MatchingLabels model.LabelNames
// On includes the given label names from matching,
// rather than excluding them.
On bool
// Include contains additional labels that should be included in
// the result from the side with the lower cardinality.
Include model.LabelNames
}
// Visitor allows visiting a Node and its child nodes. The Visit method is
// invoked for each node encountered by Walk. If the result visitor w is not
// nil, Walk visits each of the children of node with the visitor w, followed
// by a call of w.Visit(nil).
type Visitor interface {
Visit(node Node) (w Visitor)
}
// Walk traverses an AST in depth-first order: It starts by calling
// v.Visit(node); node must not be nil. If the visitor w returned by
// v.Visit(node) is not nil, Walk is invoked recursively with visitor
// w for each of the non-nil children of node, followed by a call of
// w.Visit(nil).
func Walk(v Visitor, node Node) {
if v = v.Visit(node); v == nil {
return
}
switch n := node.(type) {
case Statements:
for _, s := range n {
Walk(v, s)
}
case *AlertStmt:
Walk(v, n.Expr)
case *EvalStmt:
Walk(v, n.Expr)
case *RecordStmt:
Walk(v, n.Expr)
case Expressions:
for _, e := range n {
Walk(v, e)
}
case *AggregateExpr:
Walk(v, n.Expr)
case *BinaryExpr:
Walk(v, n.LHS)
Walk(v, n.RHS)
case *Call:
Walk(v, n.Args)
case *ParenExpr:
Walk(v, n.Expr)
case *UnaryExpr:
Walk(v, n.Expr)
case *MatrixSelector, *NumberLiteral, *StringLiteral, *VectorSelector:
// nothing to do
default:
panic(fmt.Errorf("promql.Walk: unhandled node type %T", node))
}
v.Visit(nil)
}
type inspector func(Node) bool
func (f inspector) Visit(node Node) Visitor {
if f(node) {
return f
}
return nil
}
// Inspect traverses an AST in depth-first order: It starts by calling
// f(node); node must not be nil. If f returns true, Inspect invokes f
// for all the non-nil children of node, recursively.
func Inspect(node Node, f func(Node) bool) {
Walk(inspector(f), node)
}