prometheus/promql/ast.go
Tobias Guggenmos d0cff29749 PromQL: Reduce Code duplication in AST traversion (#6362)
* promql: Add Children function for easier AST traversion

Signed-off-by: Tobias Guggenmos <tguggenm@redhat.com>
2019-11-25 11:41:59 +00:00

326 lines
9.5 KiB
Go

// 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 (
"time"
"github.com/pkg/errors"
"github.com/prometheus/prometheus/pkg/labels"
"github.com/prometheus/prometheus/storage"
)
// 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()
}
// 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 time.Time
// Time between two evaluated instants for the range [Start:End].
Interval time.Duration
}
func (*EvalStmt) 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.
Type() 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.
Param Expr // Parameter used by some aggregators.
Grouping []string // The labels by which to group the Vector.
Without bool // Whether to drop the given labels rather than keep them.
}
// 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 []*labels.Matcher
// The unexpanded seriesSet populated at query preparation time.
unexpandedSeriesSet storage.SeriesSet
series []storage.Series
}
// SubqueryExpr represents a subquery.
type SubqueryExpr struct {
Expr Expr
Range time.Duration
Offset time.Duration
Step time.Duration
}
// NumberLiteral represents a number.
type NumberLiteral struct {
Val float64
}
// 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 []*labels.Matcher
// The unexpanded seriesSet populated at query preparation time.
unexpandedSeriesSet storage.SeriesSet
series []storage.Series
}
func (e *AggregateExpr) Type() ValueType { return ValueTypeVector }
func (e *Call) Type() ValueType { return e.Func.ReturnType }
func (e *MatrixSelector) Type() ValueType { return ValueTypeMatrix }
func (e *SubqueryExpr) Type() ValueType { return ValueTypeMatrix }
func (e *NumberLiteral) Type() ValueType { return ValueTypeScalar }
func (e *ParenExpr) Type() ValueType { return e.Expr.Type() }
func (e *StringLiteral) Type() ValueType { return ValueTypeString }
func (e *UnaryExpr) Type() ValueType { return e.Expr.Type() }
func (e *VectorSelector) Type() ValueType { return ValueTypeVector }
func (e *BinaryExpr) Type() ValueType {
if e.LHS.Type() == ValueTypeScalar && e.RHS.Type() == ValueTypeScalar {
return ValueTypeScalar
}
return ValueTypeVector
}
func (*AggregateExpr) expr() {}
func (*BinaryExpr) expr() {}
func (*Call) expr() {}
func (*MatrixSelector) expr() {}
func (*SubqueryExpr) 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
// MatchingLabels contains the labels which define equality of a pair of
// elements from the Vectors.
MatchingLabels []string
// 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 []string
}
// Visitor allows visiting a Node and its child nodes. The Visit method is
// invoked for each node with the path leading to the node provided additionally.
// If the result visitor w is not nil and no error, Walk visits each of the children
// of node with the visitor w, followed by a call of w.Visit(nil, nil).
type Visitor interface {
Visit(node Node, path []Node) (w Visitor, err error)
}
// Walk traverses an AST in depth-first order: It starts by calling
// v.Visit(node, path); node must not be nil. If the visitor w returned by
// v.Visit(node, path) is not nil and the visitor returns no error, Walk is
// invoked recursively with visitor w for each of the non-nil children of node,
// followed by a call of w.Visit(nil), returning an error
// As the tree is descended the path of previous nodes is provided.
func Walk(v Visitor, node Node, path []Node) error {
var err error
if v, err = v.Visit(node, path); v == nil || err != nil {
return err
}
path = append(path, node)
for _, e := range Children(node) {
if err := Walk(v, e, path); err != nil {
return err
}
}
_, err = v.Visit(nil, nil)
return err
}
type inspector func(Node, []Node) error
func (f inspector) Visit(node Node, path []Node) (Visitor, error) {
if err := f(node, path); err != nil {
return nil, err
}
return f, nil
}
// Inspect traverses an AST in depth-first order: It starts by calling
// f(node, path); node must not be nil. If f returns a nil error, Inspect invokes f
// for all the non-nil children of node, recursively.
func Inspect(node Node, f inspector) {
//nolint: errcheck
Walk(inspector(f), node, nil)
}
// Children returns a list of all child nodes of a syntax tree node.
func Children(node Node) []Node {
// For some reasons these switches have significantly better performance than interfaces
switch n := node.(type) {
case *EvalStmt:
return []Node{n.Expr}
case Expressions:
// golang cannot convert slices of interfaces
ret := make([]Node, len(n))
for i, e := range n {
ret[i] = e
}
return ret
case *AggregateExpr:
// While this does not look nice, it should avoid unnecessary allocations
// caused by slice resizing
if n.Expr == nil && n.Param == nil {
return nil
} else if n.Expr == nil {
return []Node{n.Param}
} else if n.Param == nil {
return []Node{n.Expr}
} else {
return []Node{n.Expr, n.Param}
}
case *BinaryExpr:
return []Node{n.LHS, n.RHS}
case *Call:
// golang cannot convert slices of interfaces
ret := make([]Node, len(n.Args))
for i, e := range n.Args {
ret[i] = e
}
return ret
case *SubqueryExpr:
return []Node{n.Expr}
case *ParenExpr:
return []Node{n.Expr}
case *UnaryExpr:
return []Node{n.Expr}
case *MatrixSelector, *NumberLiteral, *StringLiteral, *VectorSelector:
// nothing to do
return []Node{}
default:
panic(errors.Errorf("promql.Children: unhandled node type %T", node))
}
}