场景问题
最近在做大模型的加载，加载文件的时候会解析出这个文件有多少个mesh, line, parameter, 而后都会存在一个变量中去保护这个关系:
const detailedList = {
mesh: Array,
line: Array,
parameter: Array
}这样会导致这个内存吃紧，毕竟间接存了好几 G 的数据信息。
那还有一种说法是，文件加载过去间接就渲染不就行了吗？
然而这样会导致 DC 过多, CPU吃不消。
IndexDB
应用 indexDB 来充当一个相似 内存 的性能，我把数据选择性的存在 indexDB 中，须要的时候再拿，这样会大大缓解内存压力。indexDB 相似 NOSQL，并不是 MYSQL 这种二维表构造, 取数据的速度是飞快的。
结构一个 Store
和大部分前端我的项目一样，我也结构了一个 store.
enum StoreType {
MEMORY,
INDEXDB
}
class Store {
/**
* 寄存在内存中的数据
*/
private memory: Map<string, any>
private readonly dbVersion: number;
/**
* indexDB
*/
private db: IDBDatabase;
private isReady: boolean;
/**
* 贮存的 value 多大才应用 indexDB 贮存，反之应用 map
*/
private readonly limitForDB: number;
/**
* 达到贮存下限后一次性删除多少条数据
*/
private readonly deleteCount: number;
/**
* 贮存下限
*/
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 加之前删除 map 中存在的 key
this.clear(key, StoreType.MEMORY)
intoIndexDB()} else {
// 退出 map 之前删除 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)
}
})
}
/**
* 查询数据库条数
*/
calculationTimesAndDelete() {const result = this.getObjectStore().count()
result.onsuccess = (e) => {
// @ts-ignore
if (e.result > this.upperStorageLimit) {this.deleteFromPrevious()
}
}
}
/**
* 达到阈值后删除最开始建设的数据
* @description 避免数据收缩
*/
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 被浏览器禁止!')
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 不确认是否初始化结束时 将查问赋值等操作包裹在此
*/
ready(callback: Function) {const step = () => {if (this.isReady) {callback && callback()
return;
}
window.requestAnimationFrame(step)
}
window.requestAnimationFrame(step)
}
/**
* @description 估算字节大小, 疏忽 key 的长度, 如果是 object 只计算 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}应用
const a = new Store();
a.ready(() => {a.set('a', { k: 'dsdsdsdsdssdsd', p: [123, 'sdsdsdsdsdsdsdvvvvvvvvv'] })
a.set('b', 123)
a.get('b')
a.get('a')
})依据客户的客户端条件适当调节 limitForDB 和upperStorageLimit