ceph-csi/vendor/github.com/google/cel-go/checker/cost.go

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// Copyright 2022 Google LLC
//
// 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 checker
import (
"math"
"github.com/google/cel-go/common"
"github.com/google/cel-go/common/overloads"
"github.com/google/cel-go/parser"
exprpb "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
)
// WARNING: Any changes to cost calculations in this file require a corresponding change in interpreter/runtimecost.go
// CostEstimator estimates the sizes of variable length input data and the costs of functions.
type CostEstimator interface {
// EstimateSize returns a SizeEstimate for the given AstNode, or nil if
// the estimator has no estimate to provide. The size is equivalent to the result of the CEL `size()` function:
// length of strings and bytes, number of map entries or number of list items.
// EstimateSize is only called for AstNodes where
// CEL does not know the size; EstimateSize is not called for values defined inline in CEL where the size
// is already obvious to CEL.
EstimateSize(element AstNode) *SizeEstimate
// EstimateCallCost returns the estimated cost of an invocation, or nil if
// the estimator has no estimate to provide.
EstimateCallCost(function, overloadID string, target *AstNode, args []AstNode) *CallEstimate
}
// CallEstimate includes a CostEstimate for the call, and an optional estimate of the result object size.
// The ResultSize should only be provided if the call results in a map, list, string or bytes.
type CallEstimate struct {
CostEstimate
ResultSize *SizeEstimate
}
// AstNode represents an AST node for the purpose of cost estimations.
type AstNode interface {
// Path returns a field path through the provided type declarations to the type of the AstNode, or nil if the AstNode does not
// represent type directly reachable from the provided type declarations.
// The first path element is a variable. All subsequent path elements are one of: field name, '@items', '@keys', '@values'.
Path() []string
// Type returns the deduced type of the AstNode.
Type() *exprpb.Type
// Expr returns the expression of the AstNode.
Expr() *exprpb.Expr
// ComputedSize returns a size estimate of the AstNode derived from information available in the CEL expression.
// For constants and inline list and map declarations, the exact size is returned. For concatenated list, strings
// and bytes, the size is derived from the size estimates of the operands. nil is returned if there is no
// computed size available.
ComputedSize() *SizeEstimate
}
type astNode struct {
path []string
t *exprpb.Type
expr *exprpb.Expr
derivedSize *SizeEstimate
}
func (e astNode) Path() []string {
return e.path
}
func (e astNode) Type() *exprpb.Type {
return e.t
}
func (e astNode) Expr() *exprpb.Expr {
return e.expr
}
func (e astNode) ComputedSize() *SizeEstimate {
if e.derivedSize != nil {
return e.derivedSize
}
var v uint64
switch ek := e.expr.GetExprKind().(type) {
case *exprpb.Expr_ConstExpr:
switch ck := ek.ConstExpr.GetConstantKind().(type) {
case *exprpb.Constant_StringValue:
v = uint64(len(ck.StringValue))
case *exprpb.Constant_BytesValue:
v = uint64(len(ck.BytesValue))
case *exprpb.Constant_BoolValue, *exprpb.Constant_DoubleValue, *exprpb.Constant_DurationValue,
*exprpb.Constant_Int64Value, *exprpb.Constant_TimestampValue, *exprpb.Constant_Uint64Value,
*exprpb.Constant_NullValue:
v = uint64(1)
default:
return nil
}
case *exprpb.Expr_ListExpr:
v = uint64(len(ek.ListExpr.GetElements()))
case *exprpb.Expr_StructExpr:
if ek.StructExpr.GetMessageName() == "" {
v = uint64(len(ek.StructExpr.GetEntries()))
}
default:
return nil
}
return &SizeEstimate{Min: v, Max: v}
}
// SizeEstimate represents an estimated size of a variable length string, bytes, map or list.
type SizeEstimate struct {
Min, Max uint64
}
// Add adds to another SizeEstimate and returns the sum.
// If add would result in an uint64 overflow, the result is math.MaxUint64.
func (se SizeEstimate) Add(sizeEstimate SizeEstimate) SizeEstimate {
return SizeEstimate{
addUint64NoOverflow(se.Min, sizeEstimate.Min),
addUint64NoOverflow(se.Max, sizeEstimate.Max),
}
}
// Multiply multiplies by another SizeEstimate and returns the product.
// If multiply would result in an uint64 overflow, the result is math.MaxUint64.
func (se SizeEstimate) Multiply(sizeEstimate SizeEstimate) SizeEstimate {
return SizeEstimate{
multiplyUint64NoOverflow(se.Min, sizeEstimate.Min),
multiplyUint64NoOverflow(se.Max, sizeEstimate.Max),
}
}
// MultiplyByCostFactor multiplies a SizeEstimate by a cost factor and returns the CostEstimate with the
// nearest integer of the result, rounded up.
func (se SizeEstimate) MultiplyByCostFactor(costPerUnit float64) CostEstimate {
return CostEstimate{
multiplyByCostFactor(se.Min, costPerUnit),
multiplyByCostFactor(se.Max, costPerUnit),
}
}
// MultiplyByCost multiplies by the cost and returns the product.
// If multiply would result in an uint64 overflow, the result is math.MaxUint64.
func (se SizeEstimate) MultiplyByCost(cost CostEstimate) CostEstimate {
return CostEstimate{
multiplyUint64NoOverflow(se.Min, cost.Min),
multiplyUint64NoOverflow(se.Max, cost.Max),
}
}
// Union returns a SizeEstimate that encompasses both input the SizeEstimate.
func (se SizeEstimate) Union(size SizeEstimate) SizeEstimate {
result := se
if size.Min < result.Min {
result.Min = size.Min
}
if size.Max > result.Max {
result.Max = size.Max
}
return result
}
// CostEstimate represents an estimated cost range and provides add and multiply operations
// that do not overflow.
type CostEstimate struct {
Min, Max uint64
}
// Add adds the costs and returns the sum.
// If add would result in an uint64 overflow for the min or max, the value is set to math.MaxUint64.
func (ce CostEstimate) Add(cost CostEstimate) CostEstimate {
return CostEstimate{
addUint64NoOverflow(ce.Min, cost.Min),
addUint64NoOverflow(ce.Max, cost.Max),
}
}
// Multiply multiplies by the cost and returns the product.
// If multiply would result in an uint64 overflow, the result is math.MaxUint64.
func (ce CostEstimate) Multiply(cost CostEstimate) CostEstimate {
return CostEstimate{
multiplyUint64NoOverflow(ce.Min, cost.Min),
multiplyUint64NoOverflow(ce.Max, cost.Max),
}
}
// MultiplyByCostFactor multiplies a CostEstimate by a cost factor and returns the CostEstimate with the
// nearest integer of the result, rounded up.
func (ce CostEstimate) MultiplyByCostFactor(costPerUnit float64) CostEstimate {
return CostEstimate{
multiplyByCostFactor(ce.Min, costPerUnit),
multiplyByCostFactor(ce.Max, costPerUnit),
}
}
// Union returns a CostEstimate that encompasses both input the CostEstimates.
func (ce CostEstimate) Union(size CostEstimate) CostEstimate {
result := ce
if size.Min < result.Min {
result.Min = size.Min
}
if size.Max > result.Max {
result.Max = size.Max
}
return result
}
// addUint64NoOverflow adds non-negative ints. If the result is exceeds math.MaxUint64, math.MaxUint64
// is returned.
func addUint64NoOverflow(x, y uint64) uint64 {
if y > 0 && x > math.MaxUint64-y {
return math.MaxUint64
}
return x + y
}
// multiplyUint64NoOverflow multiplies non-negative ints. If the result is exceeds math.MaxUint64, math.MaxUint64
// is returned.
func multiplyUint64NoOverflow(x, y uint64) uint64 {
if x > 0 && y > 0 && x > math.MaxUint64/y {
return math.MaxUint64
}
return x * y
}
// multiplyByFactor multiplies an integer by a cost factor float and returns the nearest integer value, rounded up.
func multiplyByCostFactor(x uint64, y float64) uint64 {
xFloat := float64(x)
if xFloat > 0 && y > 0 && xFloat > math.MaxUint64/y {
return math.MaxUint64
}
return uint64(math.Ceil(xFloat * y))
}
var (
selectAndIdentCost = CostEstimate{Min: common.SelectAndIdentCost, Max: common.SelectAndIdentCost}
constCost = CostEstimate{Min: common.ConstCost, Max: common.ConstCost}
createListBaseCost = CostEstimate{Min: common.ListCreateBaseCost, Max: common.ListCreateBaseCost}
createMapBaseCost = CostEstimate{Min: common.MapCreateBaseCost, Max: common.MapCreateBaseCost}
createMessageBaseCost = CostEstimate{Min: common.StructCreateBaseCost, Max: common.StructCreateBaseCost}
)
type coster struct {
// exprPath maps from Expr Id to field path.
exprPath map[int64][]string
// iterRanges tracks the iterRange of each iterVar.
iterRanges iterRangeScopes
// computedSizes tracks the computed sizes of call results.
computedSizes map[int64]SizeEstimate
checkedExpr *exprpb.CheckedExpr
estimator CostEstimator
}
// Use a stack of iterVar -> iterRange Expr Ids to handle shadowed variable names.
type iterRangeScopes map[string][]int64
func (vs iterRangeScopes) push(varName string, expr *exprpb.Expr) {
vs[varName] = append(vs[varName], expr.GetId())
}
func (vs iterRangeScopes) pop(varName string) {
varStack := vs[varName]
vs[varName] = varStack[:len(varStack)-1]
}
func (vs iterRangeScopes) peek(varName string) (int64, bool) {
varStack := vs[varName]
if len(varStack) > 0 {
return varStack[len(varStack)-1], true
}
return 0, false
}
// Cost estimates the cost of the parsed and type checked CEL expression.
func Cost(checker *exprpb.CheckedExpr, estimator CostEstimator) CostEstimate {
c := coster{
checkedExpr: checker,
estimator: estimator,
exprPath: map[int64][]string{},
iterRanges: map[string][]int64{},
computedSizes: map[int64]SizeEstimate{},
}
return c.cost(checker.GetExpr())
}
func (c *coster) cost(e *exprpb.Expr) CostEstimate {
if e == nil {
return CostEstimate{}
}
var cost CostEstimate
switch e.GetExprKind().(type) {
case *exprpb.Expr_ConstExpr:
cost = constCost
case *exprpb.Expr_IdentExpr:
cost = c.costIdent(e)
case *exprpb.Expr_SelectExpr:
cost = c.costSelect(e)
case *exprpb.Expr_CallExpr:
cost = c.costCall(e)
case *exprpb.Expr_ListExpr:
cost = c.costCreateList(e)
case *exprpb.Expr_StructExpr:
cost = c.costCreateStruct(e)
case *exprpb.Expr_ComprehensionExpr:
cost = c.costComprehension(e)
default:
return CostEstimate{}
}
return cost
}
func (c *coster) costIdent(e *exprpb.Expr) CostEstimate {
identExpr := e.GetIdentExpr()
// build and track the field path
if iterRange, ok := c.iterRanges.peek(identExpr.GetName()); ok {
switch c.checkedExpr.TypeMap[iterRange].GetTypeKind().(type) {
case *exprpb.Type_ListType_:
c.addPath(e, append(c.exprPath[iterRange], "@items"))
case *exprpb.Type_MapType_:
c.addPath(e, append(c.exprPath[iterRange], "@keys"))
}
} else {
c.addPath(e, []string{identExpr.GetName()})
}
return selectAndIdentCost
}
func (c *coster) costSelect(e *exprpb.Expr) CostEstimate {
sel := e.GetSelectExpr()
var sum CostEstimate
if sel.GetTestOnly() {
return sum
}
sum = sum.Add(c.cost(sel.GetOperand()))
targetType := c.getType(sel.GetOperand())
switch kindOf(targetType) {
case kindMap, kindObject, kindTypeParam:
sum = sum.Add(selectAndIdentCost)
}
// build and track the field path
c.addPath(e, append(c.getPath(sel.GetOperand()), sel.GetField()))
return sum
}
func (c *coster) costCall(e *exprpb.Expr) CostEstimate {
call := e.GetCallExpr()
target := call.GetTarget()
args := call.GetArgs()
var sum CostEstimate
argTypes := make([]AstNode, len(args))
argCosts := make([]CostEstimate, len(args))
for i, arg := range args {
argCosts[i] = c.cost(arg)
argTypes[i] = c.newAstNode(arg)
}
ref := c.checkedExpr.ReferenceMap[e.GetId()]
if ref == nil || len(ref.GetOverloadId()) == 0 {
return CostEstimate{}
}
var targetType AstNode
if target != nil {
if call.Target != nil {
sum = sum.Add(c.cost(call.GetTarget()))
targetType = c.newAstNode(call.GetTarget())
}
}
// Pick a cost estimate range that covers all the overload cost estimation ranges
fnCost := CostEstimate{Min: uint64(math.MaxUint64), Max: 0}
var resultSize *SizeEstimate
for _, overload := range ref.GetOverloadId() {
overloadCost := c.functionCost(call.GetFunction(), overload, &targetType, argTypes, argCosts)
fnCost = fnCost.Union(overloadCost.CostEstimate)
if overloadCost.ResultSize != nil {
if resultSize == nil {
resultSize = overloadCost.ResultSize
} else {
size := resultSize.Union(*overloadCost.ResultSize)
resultSize = &size
}
}
// build and track the field path for index operations
switch overload {
case overloads.IndexList:
if len(args) > 0 {
c.addPath(e, append(c.getPath(args[0]), "@items"))
}
case overloads.IndexMap:
if len(args) > 0 {
c.addPath(e, append(c.getPath(args[0]), "@values"))
}
}
}
if resultSize != nil {
c.computedSizes[e.GetId()] = *resultSize
}
return sum.Add(fnCost)
}
func (c *coster) costCreateList(e *exprpb.Expr) CostEstimate {
create := e.GetListExpr()
var sum CostEstimate
for _, e := range create.GetElements() {
sum = sum.Add(c.cost(e))
}
return sum.Add(createListBaseCost)
}
func (c *coster) costCreateStruct(e *exprpb.Expr) CostEstimate {
str := e.GetStructExpr()
if str.MessageName != "" {
return c.costCreateMessage(e)
}
return c.costCreateMap(e)
}
func (c *coster) costCreateMap(e *exprpb.Expr) CostEstimate {
mapVal := e.GetStructExpr()
var sum CostEstimate
for _, ent := range mapVal.GetEntries() {
key := ent.GetMapKey()
sum = sum.Add(c.cost(key))
sum = sum.Add(c.cost(ent.GetValue()))
}
return sum.Add(createMapBaseCost)
}
func (c *coster) costCreateMessage(e *exprpb.Expr) CostEstimate {
msgVal := e.GetStructExpr()
var sum CostEstimate
for _, ent := range msgVal.GetEntries() {
sum = sum.Add(c.cost(ent.GetValue()))
}
return sum.Add(createMessageBaseCost)
}
func (c *coster) costComprehension(e *exprpb.Expr) CostEstimate {
comp := e.GetComprehensionExpr()
var sum CostEstimate
sum = sum.Add(c.cost(comp.GetIterRange()))
sum = sum.Add(c.cost(comp.GetAccuInit()))
// Track the iterRange of each IterVar for field path construction
c.iterRanges.push(comp.GetIterVar(), comp.GetIterRange())
loopCost := c.cost(comp.GetLoopCondition())
stepCost := c.cost(comp.GetLoopStep())
c.iterRanges.pop(comp.GetIterVar())
sum = sum.Add(c.cost(comp.Result))
rangeCnt := c.sizeEstimate(c.newAstNode(comp.GetIterRange()))
rangeCost := rangeCnt.MultiplyByCost(stepCost.Add(loopCost))
sum = sum.Add(rangeCost)
return sum
}
func (c *coster) sizeEstimate(t AstNode) SizeEstimate {
if l := t.ComputedSize(); l != nil {
return *l
}
if l := c.estimator.EstimateSize(t); l != nil {
return *l
}
// return an estimate of 1 for return types of set
// lengths, since strings/bytes/more complex objects could be of
// variable length
if isScalar(t.Type()) {
// TODO: since the logic for size estimation is split between
// ComputedSize and isScalar, changing one will likely require changing
// the other, so they should be merged in the future if possible
return SizeEstimate{Min: 1, Max: 1}
}
return SizeEstimate{Min: 0, Max: math.MaxUint64}
}
func (c *coster) functionCost(function, overloadID string, target *AstNode, args []AstNode, argCosts []CostEstimate) CallEstimate {
argCostSum := func() CostEstimate {
var sum CostEstimate
for _, a := range argCosts {
sum = sum.Add(a)
}
return sum
}
if est := c.estimator.EstimateCallCost(function, overloadID, target, args); est != nil {
callEst := *est
return CallEstimate{CostEstimate: callEst.Add(argCostSum())}
}
switch overloadID {
// O(n) functions
case overloads.StartsWithString, overloads.EndsWithString, overloads.StringToBytes, overloads.BytesToString:
if len(args) == 1 {
return CallEstimate{CostEstimate: c.sizeEstimate(args[0]).MultiplyByCostFactor(common.StringTraversalCostFactor).Add(argCostSum())}
}
case overloads.InList:
// If a list is composed entirely of constant values this is O(1), but we don't account for that here.
// We just assume all list containment checks are O(n).
if len(args) == 2 {
return CallEstimate{CostEstimate: c.sizeEstimate(args[1]).MultiplyByCostFactor(1).Add(argCostSum())}
}
// O(nm) functions
case overloads.MatchesString:
// https://swtch.com/~rsc/regexp/regexp1.html applies to RE2 implementation supported by CEL
if target != nil && len(args) == 1 {
// Add one to string length for purposes of cost calculation to prevent product of string and regex to be 0
// in case where string is empty but regex is still expensive.
strCost := c.sizeEstimate(*target).Add(SizeEstimate{Min: 1, Max: 1}).MultiplyByCostFactor(common.StringTraversalCostFactor)
// We don't know how many expressions are in the regex, just the string length (a huge
// improvement here would be to somehow get a count the number of expressions in the regex or
// how many states are in the regex state machine and use that to measure regex cost).
// For now, we're making a guess that each expression in a regex is typically at least 4 chars
// in length.
regexCost := c.sizeEstimate(args[0]).MultiplyByCostFactor(common.RegexStringLengthCostFactor)
return CallEstimate{CostEstimate: strCost.Multiply(regexCost).Add(argCostSum())}
}
case overloads.ContainsString:
if target != nil && len(args) == 1 {
strCost := c.sizeEstimate(*target).MultiplyByCostFactor(common.StringTraversalCostFactor)
substrCost := c.sizeEstimate(args[0]).MultiplyByCostFactor(common.StringTraversalCostFactor)
return CallEstimate{CostEstimate: strCost.Multiply(substrCost).Add(argCostSum())}
}
case overloads.LogicalOr, overloads.LogicalAnd:
lhs := argCosts[0]
rhs := argCosts[1]
// min cost is min of LHS for short circuited && or ||
argCost := CostEstimate{Min: lhs.Min, Max: lhs.Add(rhs).Max}
return CallEstimate{CostEstimate: argCost}
case overloads.Conditional:
size := c.sizeEstimate(args[1]).Union(c.sizeEstimate(args[2]))
conditionalCost := argCosts[0]
ifTrueCost := argCosts[1]
ifFalseCost := argCosts[2]
argCost := conditionalCost.Add(ifTrueCost.Union(ifFalseCost))
return CallEstimate{CostEstimate: argCost, ResultSize: &size}
case overloads.AddString, overloads.AddBytes, overloads.AddList:
if len(args) == 2 {
lhsSize := c.sizeEstimate(args[0])
rhsSize := c.sizeEstimate(args[1])
resultSize := lhsSize.Add(rhsSize)
switch overloadID {
case overloads.AddList:
// list concatenation is O(1), but we handle it here to track size
return CallEstimate{CostEstimate: CostEstimate{Min: 1, Max: 1}.Add(argCostSum()), ResultSize: &resultSize}
default:
return CallEstimate{CostEstimate: resultSize.MultiplyByCostFactor(common.StringTraversalCostFactor).Add(argCostSum()), ResultSize: &resultSize}
}
}
case overloads.LessString, overloads.GreaterString, overloads.LessEqualsString, overloads.GreaterEqualsString,
overloads.LessBytes, overloads.GreaterBytes, overloads.LessEqualsBytes, overloads.GreaterEqualsBytes,
overloads.Equals, overloads.NotEquals:
lhsCost := c.sizeEstimate(args[0])
rhsCost := c.sizeEstimate(args[1])
min := uint64(0)
smallestMax := lhsCost.Max
if rhsCost.Max < smallestMax {
smallestMax = rhsCost.Max
}
if smallestMax > 0 {
min = 1
}
// equality of 2 scalar values results in a cost of 1
return CallEstimate{CostEstimate: CostEstimate{Min: min, Max: smallestMax}.MultiplyByCostFactor(common.StringTraversalCostFactor).Add(argCostSum())}
}
// O(1) functions
// See CostTracker.costCall for more details about O(1) cost calculations
// Benchmarks suggest that most of the other operations take +/- 50% of a base cost unit
// which on an Intel xeon 2.20GHz CPU is 50ns.
return CallEstimate{CostEstimate: CostEstimate{Min: 1, Max: 1}.Add(argCostSum())}
}
func (c *coster) getType(e *exprpb.Expr) *exprpb.Type {
return c.checkedExpr.TypeMap[e.GetId()]
}
func (c *coster) getPath(e *exprpb.Expr) []string {
return c.exprPath[e.GetId()]
}
func (c *coster) addPath(e *exprpb.Expr, path []string) {
c.exprPath[e.GetId()] = path
}
func (c *coster) newAstNode(e *exprpb.Expr) *astNode {
path := c.getPath(e)
if len(path) > 0 && path[0] == parser.AccumulatorName {
// only provide paths to root vars; omit accumulator vars
path = nil
}
var derivedSize *SizeEstimate
if size, ok := c.computedSizes[e.GetId()]; ok {
derivedSize = &size
}
return &astNode{path: path, t: c.getType(e), expr: e, derivedSize: derivedSize}
}
// isScalar returns true if the given type is known to be of a constant size at
// compile time. isScalar will return false for strings (they are variable-width)
// in addition to protobuf.Any and protobuf.Value (their size is not knowable at compile time).
func isScalar(t *exprpb.Type) bool {
switch kindOf(t) {
case kindPrimitive:
if t.GetPrimitive() != exprpb.Type_STRING && t.GetPrimitive() != exprpb.Type_BYTES {
return true
}
case kindWellKnown:
if t.GetWellKnown() == exprpb.Type_DURATION || t.GetWellKnown() == exprpb.Type_TIMESTAMP {
return true
}
}
return false
}