Question

我看了看，到处都看，但是IndexedDb并不是很有名。我有一个名为orders的对象库，它带有一个自动生成的密钥，每个订单的结构如下：

{"dealername":"something","dealerid":num,"totalbill":num,"items":[{},{}]}

现在，由于objectstore订单可以包含多个具有相同dealerid的订单，我如何获得具有特定dealerid的所有订单？

抱歉，对于noob问题，我来自SQL背景。感谢

Answer 1

在dealerid上创建索引。
在dealerid索引上打开一个游标并迭代。

以下是一些非常简单的代码，可以帮助您入门：

function onUpgradeNeeded(event) {
  var db = event.target.result;

  var orderStore = db.createObjectStore('orders', ...);

  // Create the index on dealerid here
  orderStore.createIndex('dealeridindex', 'dealerid');
}

function queryOrdersByDealerID(db, id, onOrder, onComplete) {
  var tx = db.transaction('orders');
  tx.onComplete = onComplete;
  var orders = tx.objectStore('orders');
  var index = orders.index('dealeridindex');
  var request = index.openCursor(id);
  // You could also do this, if you wanted, it is identical:
  // var request = index.openCursor(IDBKeyRange.only(id));

  request.onsuccess = function(event) {
    var cursor = event.target.result;
    if(!cursor) return;
    onOrder(cursor.value);
    cursor.continue();
  };
}

// Now to use it:
var openRequest = indexedDB.open('dbname', version);

// Attach our upgrade handler that gets called when higher version found
openRequest.onupgradeneeded = onUpgradeNeeded;

// Now do a query
openRequest.onsuccess = function(event) {
  // event.target === openRequest === this
  // use whatever you prefer, e.g. this.result or openRequest.result
  var openDatabaseConnection = event.target.result;

  var someId = 5;

  function handleOrder(order){
    console.log('Order %o', order);
  }

  function whenAllMatchingOrdersIterated(event) {
    console.log('Finished iterating over orders');
  }

  // 'execute' the query
  queryOrdersByDealerID(openDatabaseConnection, someId,
    handleOrder, whenAllMatchingOrdersIterated);
}

Indexeddb搜索具有特定字段的所有订单

1 个答案: