web网站使用indexedDB缓存大数量案例

前言及背景

indexedDB 是 html5 标准引入的web数据持久化方案之一，现代浏览器大多按照标准对其进行了实现，我在新的项目中用到它来作为持久化数据存储，由于最近在web端项目，每次web前端需要实时计算中间成果预计18G的中间过度数据，预计最终每次生成200M以上的结果数据，在此过程耗时30多秒，需要优化访问速度，仔细分析了算法没有办法在优化了，只能想办法缓存结果数据了，最后找了一圈，最终选择了indexedDB作为最终的缓存方案（IE浏览器不支持）。

示例代码：

// debugger;
  var date1=new Date();  //开始时间
        //获取刻度，10段11刻度
  let model = "exponential";//gaussian\spherical\exponential
  let sigma2 = 0, alpha = 100;
  debugger;
  
  let variogram = kriging.train(t, x, y, model, sigma2, alpha);

   let txydata = {"t":t,"x":x,"y":y};
   let key = MD5.hex_md5(JSON.stringify(txydata));
  
    var request = window.indexedDB.open('mydb', 1);
    request.onerror = function (event) {
        console.log('数据库打开报错');
    };

    var db;
    
    request.onupgradeneeded = function (event) {
        db = event.target.result;
        console.log('数据库版本有更新');
        var objectStore;
        if (!db.objectStoreNames.contains('krigings')) {
            objectStore = db.createObjectStore('krigings', {
                    keyPath: "id",
                    autoIncrement: true
                });
            objectStore.createIndex('key', 'key', { unique: true });
            objectStore.createIndex('data', 'data', { unique: false });
            objectStore.transaction.oncomplete = function(event) {
                console.log('数据库版本更新成功！');
            }
        }
    };

    console.log("添加数据");
    request = window.indexedDB.open('mydb', 1);
    request.onerror = function (event) {
        console.log('数据库打开报错');
    };

    request.onsuccess = function(event) {
        console.log("数据库打开成功");
        db = event.target.result;
        let requestAdd = db.transaction(['krigings'], 'readwrite').objectStore('krigings')
                        .add({key: key, data: JSON.stringify( variogram )});

            requestAdd.onsuccess = function (event) {
                console.log('数据写入成功');
            };

            requestAdd.onerror = function (event) {
                console.log('数据写入失败');
            }
    }

    console.log("读取数据");
    request = window.indexedDB.open('mydb', 1);
    request.onerror = function (event) {
        console.log('数据库打开报错');
    };
    request.onsuccess = function(event) {
        console.log("数据库打开成功");
        db = event.target.result;
        
        let objectStore = db.transaction(['krigings'], "readonly").objectStore('krigings');
        var index = objectStore.index('key'); //指定索引
        var req =  index.get(key); //按照指定索引查询数据
     
            req.onsuccess = function(event) {
                console.log("获取成功");
                console.log("key:"+event.target.result.key);
                console.log("data:"+event.target.result.data);
            };

            req.onerror = function() {
                console.log("获取失败");
            };
    }

  var date2=new Date();    //结束时间
   console.log(date2.getTime()-date1.getTime());