場景問題
最近在做大模型的載入，載入檔案的時候會解析出這個檔案有多少個mesh, line, parameter, 然後都會存在一個變數中去維護這個關係:
const detailedList = {
mesh: Array,
line: Array,
parameter: Array
}這樣會導致這個記憶體吃緊，畢竟直接存了好幾G的資料資訊。
那還有一種說法是， 檔案載入過來直接就渲染不就行了嗎？
但是這樣會導致DC過多, CPU吃不消。
IndexDB
使用indexDB來充當一個類似記憶體的功能， 我把資料選擇性的存在indexDB中，需要的時候再拿，這樣會大大緩解記憶體壓力。indexDB類似NOSQL，並不是MYSQL這種二維表結構, 取資料的速度是飛快的。
構造一個Store
和大部分前端專案一樣，我也構造了一個store.
enum StoreType {
MEMORY,
INDEXDB
}
class Store {
/**
* 存放在記憶體中的資料
*/
private memory: Map<string, any>
private readonly dbVersion: number;
/**
* indexDB
*/
private db: IDBDatabase;
private isReady: boolean;
/**
* 儲存的value多大才使用indexDB儲存，反之使用map
*/
private readonly limitForDB: number;
/**
* 達到儲存上限後一次性刪除多少條資料
*/
private readonly deleteCount: number;
/**
* 儲存上限
*/
private readonly upperStorageLimit: number;
constructor(dbVersion = 1, limitForDB?: number) {
this.isReady = false
this.dbVersion = dbVersion
this.initIndexDB()
this.memory = new Map()
this.limitForDB = limitForDB || 30
this.upperStorageLimit = 10000
this.deleteCount = 20
}
set(key: string, value: any, type?: StoreType) {
const intoMemory = () => {
this.memory.set(key, value)
}
const intoIndexDB = () => {
const objectStore = this.getObjectStore();
objectStore.put({id: key, value}, key);
this.calculationTimesAndDelete();
}
if (typeof type !== 'undefined') {
type === StoreType.INDEXDB ? intoIndexDB() : intoMemory()
} else {
if (Store.sizeOf(value) > this.limitForDB) {
// indexDB加之前刪除map中存在的key
this.clear(key, StoreType.MEMORY)
intoIndexDB()
} else {
// 加入map之前刪除indexDB中存在的key
this.clear(key, StoreType.INDEXDB)
intoMemory()
}
}
}
get(key: string, type?: StoreType): Promise<any> {
return new Promise((resolve, reject) => {
const fromMemory = (key) => {
resolve(this.memory.get(key))
}
const fromIndexDB = (key) => {
const objectStore = this.getObjectStore();
const index = objectStore.index("id");
const res = index.get(key);
res.onsuccess = (e) => {
// @ts-ignore
resolve(e.target.result.value)
}
res.onerror = (e) => {
reject(e)
}
}
if (typeof type !== 'undefined') {
type === StoreType.INDEXDB ? fromIndexDB(key) : fromMemory(key)
} else {
this.memory.has(key) ? fromMemory(key) : fromIndexDB(key)
}
})
}
/**
* 查詢資料庫條數
*/
calculationTimesAndDelete() {
const result = this.getObjectStore().count()
result.onsuccess = (e) => {
// @ts-ignore
if (e.result > this.upperStorageLimit) {
this.deleteFromPrevious()
}
}
}
/**
* 達到閾值後刪除最開始建立的資料
* @description 防止資料膨脹
*/
deleteFromPrevious() {
const objectStore = this.getObjectStore()
const request = objectStore.openCursor();
let count = 0
request.onsuccess = (event) => {
// @ts-ignore
const cursor = event.target.result
if (cursor) {
if (count === this.deleteCount) return;
count++;
objectStore.delete(cursor.key)
cursor.continue()
}
}
}
getObjectStore() {
const transaction = this.db.transaction(["store"], "readwrite");
return transaction.objectStore("store")
}
clear(key: string, type?: StoreType) {
const fromMemoryDel = () => this.memory.delete(key)
const fromIndexDBDel = () => {
const objectStore = this.getObjectStore();
objectStore.delete(key)
}
if (typeof type !== 'undefined') {
type === StoreType.INDEXDB ? fromIndexDBDel() : fromMemoryDel()
} else {
this.memory.has(key) ? fromMemoryDel() : fromIndexDBDel()
}
}
initIndexDB() {
// @ts-ignore
const indexedDB = window.indexedDB || window.webkitIndexedDB || window.mozIndexedDB || window.OIndexedDB || window.msIndexedDB
if (!indexedDB) {
alert('indexDB被瀏覽器禁止!')
throw new Error('indexDB forbidden in the browser!')
}
const request = indexedDB.open("elephantFiles", this.dbVersion)
request.onerror = function () {
throw new Error('Error creating/accessing IndexedDB database');
}
request.onsuccess = event => {
// @ts-ignore
this.db = event.target.result as IDBDatabase;
this.isReady = true
}
request.onupgradeneeded = (event) => {
console.log('database upgradeneeded!')
// @ts-ignore
const db = event.target.result as IDBDatabase;
if (!db.objectStoreNames.contains('store')) {
const store = db.createObjectStore('store')
store.createIndex('id', 'id')
}
}
}
/**
* @description 不確認是否初始化完畢時 將查詢賦值等操作包裹在此
*/
ready(callback: Function) {
const step = () => {
if (this.isReady) {
callback && callback()
return;
}
window.requestAnimationFrame(step)
}
window.requestAnimationFrame(step)
}
/**
* @description 估算位元組大小, 忽略key的長度, 如果是object只計算value, 比JSON.stringify更快
*/
static sizeOf(value): number {
const typeSizes = {
"undefined": () => 0,
"boolean": () => 4,
"number": () => 8,
"string": item => 2 * item.length,
"object": item => !item ? 0 : Object
.keys(item)
.reduce((total, key) => size(key) + size(item[key]) + total, 0)
};
const size = value => typeSizes[typeof value](value);
return size(value)
}
}
export {StoreType, Store}使用
const a = new Store();
a.ready(() => {
a.set('a', { k: 'dsdsdsdsdssdsd', p: [123, 'sdsdsdsdsdsdsdvvvvvvvvv'] })
a.set('b', 123)
a.get('b')
a.get('a')
})根據客戶的客戶端條件適當調節limitForDB和upperStorageLimit