batch_save.go

/*
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements.  See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You 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 helper

import (
	"fmt"
	"reflect"
	"strings"

	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

// Insert data by batch can increase database performance drastically, this class aim to make batch-save easier,
// It takes care the database operation for specified `slotType`, records got saved into database whenever cache hits
// The `size` limit, remember to call the `Close` method to save the last batch
type BatchSave struct {
	slotType reflect.Type
	// slots can not be []interface{}, because gorm wouldn't take it
	// I'm guessing the reason is the type information lost when converted to interface{}
	slots      reflect.Value
	db         *gorm.DB
	current    int
	size       int
	valueIndex map[string]int
}

func NewBatchSave(db *gorm.DB, slotType reflect.Type, size int) (*BatchSave, error) {
	if slotType.Kind() != reflect.Ptr {
		return nil, fmt.Errorf("slotType must be a pointer")
	}
	if !hasPrimaryKey(slotType) {
		return nil, fmt.Errorf("no primary key")
	}
	return &BatchSave{
		slotType:   slotType,
		slots:      reflect.MakeSlice(reflect.SliceOf(slotType), size, size),
		db:         db,
		size:       size,
		valueIndex: make(map[string]int),
	}, nil
}

func (c *BatchSave) Add(slot interface{}) error {
	// type checking
	if reflect.TypeOf(slot) != c.slotType {
		return fmt.Errorf("sub cache type mismatched")
	}
	if reflect.ValueOf(slot).Kind() != reflect.Ptr {
		return fmt.Errorf("slot is not a pointer")
	}
	// deduplication
	key := getPrimaryKeyValue(slot)

	if key != "" {
		if index, ok := c.valueIndex[key]; !ok {
			c.valueIndex[key] = c.current
		} else {
			c.slots.Index(index).Set(reflect.ValueOf(slot))
			return nil
		}
	}
	c.slots.Index(c.current).Set(reflect.ValueOf(slot))
	c.current++
	// flush out into database if max outed
	if c.current == c.size {
		return c.Flush()
	}
	return nil
}

func (c *BatchSave) Flush() error {
	err := c.db.Clauses(clause.OnConflict{UpdateAll: true}).Create(c.slots.Slice(0, c.current).Interface()).Error
	if err != nil {
		return err
	}
	c.current = 0
	c.valueIndex = make(map[string]int)
	return nil
}

func (c *BatchSave) Close() error {
	if c.current > 0 {
		return c.Flush()
	}
	return nil
}

func isPrimaryKey(f reflect.StructField) bool {
	tag := strings.TrimSpace(f.Tag.Get("gorm"))
	return strings.HasPrefix(strings.ToLower(tag), "primarykey")
}

func hasPrimaryKey(ifv reflect.Type) bool {
	if ifv.Kind() == reflect.Ptr {
		ifv = ifv.Elem()
	}
	for i := 0; i < ifv.NumField(); i++ {
		v := ifv.Field(i)
		switch v.Type.Kind() {
		case reflect.Struct:
			ok := hasPrimaryKey(v.Type)
			if ok {
				return true
			}
		default:
			if ok := isPrimaryKey(v); ok {
				return true
			}
		}
	}
	return false
}

func getPrimaryKeyValue(iface interface{}) string {
	var ss []string
	ifv := reflect.ValueOf(iface)
	if ifv.Kind() == reflect.Ptr {
		ifv = ifv.Elem()
	}
	for i := 0; i < ifv.NumField(); i++ {
		v := ifv.Field(i)
		switch v.Kind() {
		case reflect.Struct:
			s := getPrimaryKeyValue(v.Interface())
			if s != "" {
				ss = append(ss, s)
			}
		default:
			if isPrimaryKey(ifv.Type().Field(i)) {
				s := fmt.Sprintf("%v", v.Interface())
				if s != "" {
					ss = append(ss, s)
				}
			}
		}
	}
	return strings.Join(ss, ":")
}