tidb constraints 源码
tidb constraints 代码
文件路径：/ddl/placement/constraints.go
// Copyright 2021 PingCAP, Inc.
//
// 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 placement
import (
"fmt"
"strings"
"gopkg.in/yaml.v2"
)
// Constraints is a slice of constraints.
type Constraints []Constraint
// NewConstraints will check each labels, and build the Constraints.
func NewConstraints(labels []string) (Constraints, error) {
if len(labels) == 0 {
return nil, nil
}
constraints := make(Constraints, 0, len(labels))
for _, str := range labels {
label, err := NewConstraint(strings.TrimSpace(str))
if err != nil {
return constraints, err
}
err = constraints.Add(label)
if err != nil {
return constraints, err
}
}
return constraints, nil
}
// NewConstraintsFromYaml will transform parse the raw 'array' constraints and call NewConstraints.
// Refer to https://github.com/pingcap/tidb/blob/master/docs/design/2020-06-24-placement-rules-in-sql.md.
func NewConstraintsFromYaml(c []byte) (Constraints, error) {
constraints := []string{}
err := yaml.UnmarshalStrict(c, &constraints)
if err != nil {
return nil, ErrInvalidConstraintsFormat
}
return NewConstraints(constraints)
}
// NewConstraintsDirect is a helper for creating new constraints from individual constraint.
func NewConstraintsDirect(c ...Constraint) Constraints {
return c
}
// Restore converts label constraints to a string.
func (constraints *Constraints) Restore() (string, error) {
var sb strings.Builder
for i, constraint := range *constraints {
if i > 0 {
sb.WriteByte(',')
}
sb.WriteByte('"')
conStr, err := constraint.Restore()
if err != nil {
return "", err
}
sb.WriteString(conStr)
sb.WriteByte('"')
}
return sb.String(), nil
}
// Add will add a new label constraint, with validation of all constraints.
// Note that Add does not validate one single constraint.
func (constraints *Constraints) Add(label Constraint) error {
pass := true
for i := range *constraints {
cnst := (*constraints)[i]
res := label.CompatibleWith(&cnst)
if res == ConstraintCompatible {
continue
}
if res == ConstraintDuplicated {
pass = false
continue
}
s1, err := label.Restore()
if err != nil {
s1 = err.Error()
}
s2, err := cnst.Restore()
if err != nil {
s2 = err.Error()
}
return fmt.Errorf("%w: '%s' and '%s'", ErrConflictingConstraints, s1, s2)
}
if pass {
*constraints = append(*constraints, label)
}
return nil
}
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