indexedDB 最高键路径 [英] indexedDB highest keypath

问题描述

我在 indexedDB 中有一个使用 Emberjs 适配器填充的数据库.我已经设置了这样的键路径:

I have a database inside indexedDB filled using an Emberjs adapter. I have set the keypath like this:

this.addModel(App.Device, { keyPath: 'key' });

当我第一次像这样解析数据时，我的密钥会自动递增:

And my key is autoincremented when I parse my data the first time I got them like this:

data = data.map(function( item, idx ) {
    item.key = idx;
    return item;
});

在所有数据都存储在 indexedDB 中之后，我想添加更多数据，但我需要继续在我的数据中设置一个键值.

After all of the data are store inside indexedDB, I want to add some more data, but I need to get to continue to set a key value inside my data.

如何获得最高的键(在我的情况下它是一个唯一的数字(如 ID))，以便我可以增加当前数据中的键以添加到我的数据库中?

How can I get the highest key (in my case it's a unique number (like an id)), so I can increment the one the key in my current data to add to my database?

这是我想用来添加更多数据的代码示例:

Here is the sample of my code that I want to use to add more data:

var request = indexedDB.open( 'products' );
request.onsuccess = function( e ) {
    console.log('Success!');
    that.setProperties({ db: e.target.result });
    var db = e.target.result;
    var reader = new window.FileReader();
    reader.readAsDataURL(blob_);
    var img64;
    reader.onloadend = function() {
        base64data = reader.result;
        var dataImage = {
            key: 42,
            url: url_,
            base64: base64data
        }
        that.storage.saveProduct( db, dataImage );
    }
};

request.onerror = function( e ) {
    console.log('Error!');
    console.dir( e );
};

[edit] 我忘了把 saveProduct fct:

[edit] I forgot to put the saveProduct fct:

this.saveProduct = function( db, data ) {
    var transaction = db.transaction( ["App.Device"], "readwrite" );
    var store = transaction.objectStore( "App.Device" );

    var request = store.add( data );

    request.onerror = function( e ) {
        console.log("Error",e.target.error.name);
        //some type of error handler
    };

    request.onsuccess = function( e ) {
        console.log("Device saved in db");
    };
};

推荐答案

这是最后一个条目的 IDB 模式:

Here's an IDB pattern for the last entry:

1. 将光标值绑定到第一个 ID 条目.("0" 应该这样做，因为键是按字典顺序排列的.)(原始答案链接到问题 https://stackoverflow.com/a/22812410/317937 现已删除)
2. 使用反向光标(根据您的需要prev"或prevunique"方向)
3. 您的下一个条目将是最后一个条目(skip() 或 continue() 都可以)

1. Bind your cursor value to the first ID entry. ("0" should do it since keys are lexicographically ordered.) (Original answer linked to question https://stackoverflow.com/a/22812410/317937 which has now been removed)
2. Use a reverse cursor ("prev" or "prevunique" direction depending on your needs)
3. Your next entry will be the last entry (skip() or continue() either should work)

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