在IndexedDB中，有两种方法可以更新数据库中已有的对象。您可以致电IDBCursor.update或IDBObjectStore.put。
两者都接受更新的对象作为参数。
IDBCursor.update要求您先打开游标，但基本上也必须使用IDBObjectStore.put来检索先前的值。
IDBObjectStore.put无法找到要更新的对象，它将创建一个新对象，但由于它必须先检查更新，我不知道这是否会实际产生性能差异。
那么这些方法有什么区别？有什么我想念的吗？我试图制作一个测试用例来调查性能差异：
var db;
function runTest(N, cb) {
console.log("N = " + N);
// Add some fake data to object store
var tx = db.transaction("store", "readwrite");
tx.objectStore("store").clear();
for (var i = 0; i < N; i++) {
tx.objectStore("store").add({"id": i, "index":0,"guid":"21310c91-ff31-4cb9-ae68-16d48cbbd84a","isActive":false,"balance":"$1,840.25","picture":"http://placehold.it/32x32","age":33,"eyeColor":"brown","name":"Witt Fletcher","gender":"male","company":"QUILM","email":"wittfletcher@quilm.com","phone":"+1 (851) 485-2174","address":"729 Conover Street, Marenisco, Virginia, 7219","about":"Incididunt do deserunt ut quis. Exercitation et ut ad aliqua ut do sint Lorem. Aliquip sit aliquip nulla excepteur pariatur ut laborum ea dolor. Consectetur incididunt et et esse commodo id eu dolor in. Nostrud sit mollit occaecat ullamco commodo aute anim duis enim et aliqua. Aute duis nostrud do minim labore sunt mollit in voluptate aliquip sit. Aliqua aliquip non ipsum exercitation cillum irure in.\r\n","registered":"2014-07-02T03:42:57 +04:00","latitude":-65.942119,"longitude":-129.471674,"tags":["reprehenderit","nostrud","velit","exercitation","nulla","nulla","est"],"friends":[{"id":0,"name":"Kristine Francis"},{"id":1,"name":"Lizzie Ruiz"},{"id":2,"name":"Bobbie Underwood"}],"greeting":"Hello, Witt Fletcher! You have 7 unread messages.","favoriteFruit":"apple"});
}
tx.oncomplete = function () {
// Update with cursor.update
var tStart = (new Date()).getTime();
tx = db.transaction("store", "readwrite");
var store = tx.objectStore("store");
for (var i = 0; i < N; i++) {
store.openCursor(i).onsuccess = function (event) {
var cursor = event.target.result;
cursor.value.age = 34;
cursor.update(cursor.value);
};
}
tx.oncomplete = function () {
var tEnd = (new Date()).getTime();
console.log("cursor.update - " + (tEnd - tStart) + " milliseconds");
// Update with put
tStart = (new Date()).getTime();
tx = db.transaction("store", "readwrite");
store = tx.objectStore("store");
for (var i = 0; i < N; i++) {
store.openCursor(i).onsuccess = function (event) {
var cursor = event.target.result;
cursor.value.age = 34;
store.put(cursor.value);
};
}
tx.oncomplete = function () {
tEnd = (new Date()).getTime();
console.log("put - " + (tEnd - tStart) + " milliseconds");
if (cb !== undefined) {
cb();
}
};
};
};
}
request = indexedDB.open("yes5ytrye", 1);
request.onerror = function (event) { console.log(event); };
request.onupgradeneeded = function (event) {
var db = event.target.result;
db.onerror = function (event) { console.log(event); };
db.createObjectStore("store", {keyPath: "id"});
};
request.onsuccess = function (event) {
db = request.result;
db.onerror = function (event) { console.log(event); };
runTest(100, function () {
runTest(1000, function () {
runTest(10000, function () {
console.log("Done");
});
});
});
};
您可以尝试here。
在Firefox中，我输出如下：
N = 100
cursor.update - 39 milliseconds
put - 40 milliseconds
N = 1000
cursor.update - 229 milliseconds
put - 256 milliseconds
N = 10000
cursor.update - 2194 milliseconds
put - 2096 milliseconds
Done
基本上没有性能差异。当N很大时，Chrome中的结果略有不同：
N = 100
cursor.update - 51 milliseconds
put - 44 milliseconds
N = 1000
cursor.update - 414 milliseconds
put - 447 milliseconds
N = 10000
cursor.update - 13506 milliseconds
put - 22783 milliseconds
Done
但正如我上面所述，我甚至不确定这两种方法之间是否存在差异，因为它们似乎必须完全相同。
答案 0 :(得分：3)
update cursor和put之间的主要区别在于，您需要使用cursor检索要更新的元素;另一方面，当使用put语句时，您只需要知道要更新的元素的id，然后执行put函数，该函数在{{1}上定义水平。但是，此加速仅适用于将完整对象存储在内存中的情况。
我稍微更新了你的代码并加快了速度：
store
以下是我的结果：
var db;
function runTest(N, cb) {
console.log("N = " + N);
// Add some fake data to object store
var tx = db.transaction("store", "readwrite");
tx.objectStore("store").clear();
for (var i = 0; i < N; i++) {
tx.objectStore("store").add({"id": i, "index":0,"guid":"21310c91-ff31-4cb9-ae68-16d48cbbd84a","isActive":false,"balance":"$1,840.25","picture":"http://placehold.it/32x32","age":33,"eyeColor":"brown","name":"Witt Fletcher","gender":"male","company":"QUILM","email":"wittfletcher@quilm.com","phone":"+1 (851) 485-2174","address":"729 Conover Street, Marenisco, Virginia, 7219","about":"Incididunt do deserunt ut quis. Exercitation et ut ad aliqua ut do sint Lorem. Aliquip sit aliquip nulla excepteur pariatur ut laborum ea dolor. Consectetur incididunt et et esse commodo id eu dolor in. Nostrud sit mollit occaecat ullamco commodo aute anim duis enim et aliqua. Aute duis nostrud do minim labore sunt mollit in voluptate aliquip sit. Aliqua aliquip non ipsum exercitation cillum irure in.\r\n","registered":"2014-07-02T03:42:57 +04:00","latitude":-65.942119,"longitude":-129.471674,"tags":["reprehenderit","nostrud","velit","exercitation","nulla","nulla","est"],"friends":[{"id":0,"name":"Kristine Francis"},{"id":1,"name":"Lizzie Ruiz"},{"id":2,"name":"Bobbie Underwood"}],"greeting":"Hello, Witt Fletcher! You have 7 unread messages.","favoriteFruit":"apple"});
}
tx.oncomplete = function () {
// Update with cursor.update
var tStart = (new Date()).getTime();
tx = db.transaction("store", "readwrite");
var store = tx.objectStore("store");
for (var i = 0; i < N; i++) {
store.openCursor(i).onsuccess = function (event) {
var cursor = event.target.result;
cursor.value.age = 34;
cursor.update(cursor.value);
};
}
tx.oncomplete = function () {
var tEnd = (new Date()).getTime();
console.log("cursor.update - " + (tEnd - tStart) + " milliseconds");
// Update with put
tStart = (new Date()).getTime();
tx = db.transaction("store", "readwrite");
store = tx.objectStore("store");
for (var i = 0; i < N; i++) {
//you don't need the element just update
store.put({"id": i, "index":0,"guid":"21310c91-ff31-4cb9-ae68-16d48cbbd84a","isActive":false,"balance":"$1,840.25","picture":"http://placehold.it/32x32","age":33,"eyeColor":"brown","name":"Witt Fletcher","gender":"male","company":"QUILM","email":"wittfletcher@quilm.com","phone":"+1 (851) 485-2174","address":"729 Conover Street, Marenisco, Virginia, 7219","about":"Incididunt do deserunt ut quis. Exercitation et ut ad aliqua ut do sint Lorem. Aliquip sit aliquip nulla excepteur pariatur ut laborum ea dolor. Consectetur incididunt et et esse commodo id eu dolor in. Nostrud sit mollit occaecat ullamco commodo aute anim duis enim et aliqua. Aute duis nostrud do minim labore sunt mollit in voluptate aliquip sit. Aliqua aliquip non ipsum exercitation cillum irure in.\r\n","registered":"2014-07-02T03:42:57 +04:00","latitude":-65.942119,"longitude":-129.471674,"tags":["reprehenderit","nostrud","velit","exercitation","nulla","nulla","est"],"friends":[{"id":0,"name":"Kristine Francis"},{"id":1,"name":"Lizzie Ruiz"},{"id":2,"name":"Bobbie Underwood"}],"greeting":"Hello, Witt Fletcher! You have 7 unread messages.","favoriteFruit":"apple"});
}
tx.oncomplete = function () {
tEnd = (new Date()).getTime();
console.log("put - " + (tEnd - tStart) + " milliseconds");
if (cb !== undefined) {
cb();
}
};
};
};
}
request = indexedDB.open("yes5ytrye", 1);
request.onerror = function (event) { console.log(event); };
request.onupgradeneeded = function (event) {
var db = event.target.result;
db.onerror = function (event) { console.log(event); };
db.createObjectStore("store", {keyPath: "id"});
};
request.onsuccess = function (event) {
db = request.result;
db.onerror = function (event) { console.log(event); };
runTest(100, function () {
runTest(1000, function () {
runTest(10000, function () {
console.log("Done");
});
});
});
};答案 1 :(得分：2)
是的，它们都是相同的，因为它们都用来更新记录值。如果您已经知道密钥和值，请使用简单的put，否则只有一点卷积的游标更新是唯一选项。
更新记录的效果应相同。