HTML5 IndexedDB -如何将所有记录合并为一个

HTML5 IndexedDB - How to merge all records into one

本文关键字：合并 一个 记录 IndexedDB HTML5      更新时间：2023-09-26

我的想法是从服务器下载一个巨大的文件。

  1. 存储在IndexedDB中的块

  2. 下载完所有的chunk后，将所有的记录合并为一个(SQL SELECT * FROM XXX…)

  3. 保存到磁盘"saveAs()"或创建URL到IndexedDB…

(Or any idea?)

我不知道怎么做第二步。3 .

(下面是在DB中存储10,000条记录的示例以及步骤2之后的预期输出。应该是susansusansusansusansusansusansusan…)

if (transaction) {
    transaction.oncomplete = function () {
    }
    transaction.onabort = function () {
        writeToConsoleScreen("transaction aborted.");
        localDatabase.db.close();
    }
    transaction.ontimeout = function () {
        writeToConsoleScreen("transaction timeout.");
        localDatabase.db.close();
    }
    var store = transaction.objectStore(osTableName);
    if (store) {
        var req;
        var customer = {};                   
       // create ten thousand records
       for (var loop = 0; loop < 10000; loop++) {
            customer = {};
            customer.fname = 'Susan';
            req = store.add(customer);
            req.onsuccess = function (ev) {
            }
            req.onerror = function (ev) {
                writeToConsoleScreen("Failed to add record." + "  Error: " + ev.message);
            }
        }     
    }
}

<!DOCTYPE html>
<script>
var open = indexedDB.open('chunks-example');
open.onupgradeneeded = function() {
  // Create schema if necessary
  var db = open.result;
  db.createObjectStore('chunks');
};
// 1. Chunks stored into an IndexedDB.
open.onsuccess = function() {
  var db = open.result;
  var tx = db.transaction('chunks', 'readwrite');
  var store = tx.objectStore('chunks');
  for (var i = 0; i < 10; ++i) {
    // For realz, this would be via
    // XMLHttpRequest.response and async.
    var chunk = new Blob(['chunk ' + i + ''n'],
      {type: 'application/octet-stream'});
    store.put(chunk, i);
  }
  tx.oncomplete = function() { merge(db); };
};
// 2. After "download" all chunks, merge all records into one
function merge(db) {
  var tx = db.transaction('chunks');
  var store = tx.objectStore('chunks');
  var chunks = [];
  var request = store.openCursor();
  request.onsuccess = function() {
    var cursor = request.result;
    if (cursor) {
      chunks.push(cursor.value);
      cursor.continue();
    } else {
      saveAs('myfile', new Blob(chunks,
        {type: 'application/octet-stream'}));
    }
  };
}
// 3. Save into disk "saveAs()"
function saveAs(filename, blob) {
  var a = document.documentElement.appendChild(document.createElement('a'));
  a.href = URL.createObjectURL(blob);
  a.download = filename;
  a.click();
  a.parentElement.remove(a);
}
</script>
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