github.com/whtcorpsinc/milevadb-prod@v0.0.0-20211104133533-f57f4be3b597/causetstore/petri/acyclic/causet/memo/group_expr.go (about)

     1  // Copyright 2020 WHTCORPS INC, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package memo
    15  
    16  import (
    17  	"encoding/binary"
    18  	"reflect"
    19  
    20  	causetembedded "github.com/whtcorpsinc/milevadb/causet/embedded"
    21  	"github.com/whtcorpsinc/milevadb/memex"
    22  )
    23  
    24  // GroupExpr is used to causetstore all the logically equivalent memexs which
    25  // have the same root operator. Different from a normal memex, the
    26  // Children of a Group memex are memex Groups, not memexs.
    27  // Another property of Group memex is that the child Group references will
    28  // never be changed once the Group memex is created.
    29  type GroupExpr struct {
    30  	ExprNode causetembedded.LogicalCauset
    31  	Children []*Group
    32  	Group    *Group
    33  
    34  	// ExploreMark is uses to mark whether this GroupExpr has been fully
    35  	// explored by a transformation rule batch in a certain round.
    36  	ExploreMark
    37  
    38  	selfFingerprint string
    39  	// appliedMemruleSet saves transformation rules which have been applied to this
    40  	// GroupExpr, and will not be applied again. Use `uint64` which should be the
    41  	// id of a Transformation instead of `Transformation` itself to avoid import cycle.
    42  	appliedMemruleSet map[uint64]struct{}
    43  }
    44  
    45  // NewGroupExpr creates a GroupExpr based on a logical plan node.
    46  func NewGroupExpr(node causetembedded.LogicalCauset) *GroupExpr {
    47  	return &GroupExpr{
    48  		ExprNode:          node,
    49  		Children:          nil,
    50  		appliedMemruleSet: make(map[uint64]struct{}),
    51  	}
    52  }
    53  
    54  // FingerPrint gets the unique fingerprint of the Group memex.
    55  func (e *GroupExpr) FingerPrint() string {
    56  	if len(e.selfFingerprint) == 0 {
    57  		planHash := e.ExprNode.HashCode()
    58  		buffer := make([]byte, 2, 2+len(e.Children)*8+len(planHash))
    59  		binary.BigEndian.PutUint16(buffer, uint16(len(e.Children)))
    60  		for _, child := range e.Children {
    61  			var buf [8]byte
    62  			binary.BigEndian.PutUint64(buf[:], uint64(reflect.ValueOf(child).Pointer()))
    63  			buffer = append(buffer, buf[:]...)
    64  		}
    65  		buffer = append(buffer, planHash...)
    66  		e.selfFingerprint = string(buffer)
    67  	}
    68  	return e.selfFingerprint
    69  }
    70  
    71  // SetChildren sets Children of the GroupExpr.
    72  func (e *GroupExpr) SetChildren(children ...*Group) {
    73  	e.Children = children
    74  }
    75  
    76  // Schema gets GroupExpr's Schema.
    77  func (e *GroupExpr) Schema() *memex.Schema {
    78  	return e.Group.Prop.Schema
    79  }
    80  
    81  // AddAppliedMemrule adds a rule into the appliedMemruleSet.
    82  func (e *GroupExpr) AddAppliedMemrule(rule interface{}) {
    83  	ruleID := reflect.ValueOf(rule).Pointer()
    84  	e.appliedMemruleSet[uint64(ruleID)] = struct{}{}
    85  }
    86  
    87  // HasAppliedMemrule returns if the rule has been applied.
    88  func (e *GroupExpr) HasAppliedMemrule(rule interface{}) bool {
    89  	ruleID := reflect.ValueOf(rule).Pointer()
    90  	_, ok := e.appliedMemruleSet[uint64(ruleID)]
    91  	return ok
    92  }