tidb group_expr 代码
文件路径：/planner/memo/group_expr.go
/ Copyright 2018 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 memo
import (
"encoding/binary"
"reflect"
"github.com/pingcap/tidb/expression"
plannercore "github.com/pingcap/tidb/planner/core"
)
/ GroupExpr is used to store all the logically equivalent expressions which
/ have the same root operator. Different from a normal expression, the
/ Children of a Group expression are expression Groups, not expressions.
/ Another property of Group expression is that the child Group references will
/ never be changed once the Group expression is created.
type GroupExpr struct {
ExprNode plannercore.LogicalPlan
Children []*Group
Group *Group
/ ExploreMark is uses to mark whether this GroupExpr has been fully
/ explored by a transformation rule batch in a certain round.
ExploreMark
selfFingerprint string
/ appliedRuleSet saves transformation rules which have been applied to this
/ GroupExpr, and will not be applied again. Use `uint64` which should be the
/ id of a Transformation instead of `Transformation` itself to avoid import cycle.
appliedRuleSet map[uint64]struct{}
}
/ NewGroupExpr creates a GroupExpr based on a logical plan node.
func NewGroupExpr(node plannercore.LogicalPlan) *GroupExpr {
return &GroupExpr{
ExprNode: node,
Children: nil,
appliedRuleSet: make(map[uint64]struct{}),
}
}
/ FingerPrint gets the unique fingerprint of the Group expression.
func (e *GroupExpr) FingerPrint() string {
if len(e.selfFingerprint) == 0 {
planHash := e.ExprNode.HashCode()
buffer := make([]byte, 2, 2+len(e.Children)*8+len(planHash))
binary.BigEndian.PutUint16(buffer, uint16(len(e.Children)))
for _, child := range e.Children {
var buf [8]byte
binary.BigEndian.PutUint64(buf[:], uint64(reflect.ValueOf(child).Pointer()))
buffer = append(buffer, buf[:]...)
}
buffer = append(buffer, planHash...)
e.selfFingerprint = string(buffer)
}
return e.selfFingerprint
}
/ SetChildren sets Children of the GroupExpr.
func (e *GroupExpr) SetChildren(children ...*Group) {
e.Children = children
}
/ Schema gets GroupExpr's Schema.
func (e *GroupExpr) Schema() *expression.Schema {
return e.Group.Prop.Schema
}
/ AddAppliedRule adds a rule into the appliedRuleSet.
func (e *GroupExpr) AddAppliedRule(rule interface{}) {
ruleID := reflect.ValueOf(rule).Pointer()
e.appliedRuleSet[uint64(ruleID)] = struct{}{}
}
/ HasAppliedRule returns if the rule has been applied.
func (e *GroupExpr) HasAppliedRule(rule interface{}) bool {
ruleID := reflect.ValueOf(rule).Pointer()
_, ok := e.appliedRuleSet[uint64(ruleID)]
return ok
}