未捕获的InvalidStateError:无法在"IDBDatabase"上执行"transaction":正在运行版本更改事务

Question

我必须承认我对indexedDB很新

我写了一个简单的代码,indexedDB 它如下:

function go(){var req = window.indexedDB.open("Uploader", 1), db;
    req.onerror=function(e){console.log('Error')};
    req.onsuccess = function(e){db=e.target.result;};
    req.onupgradeneeded = function(e){console.log(db);
        db=e.target.result;db=e.target.result;
        var os = db.createObjectStore('Files', {keyPath:"files"});
            os.createIndex('text', 'text_file', {unique:false})
        var trans = db.transaction(['text'], "readwrite");  
        var objectstore=  trans.objectStore("text");
        var addreq = objectstore.add('Instructions.js');
            addreq.onsuccess = function(e){console.log('Success!');console.dir(e)}
    }}

它给我的错误是 Uncaught InvalidStateError: Failed to execute 'transaction' on 'IDBDatabase': A version change transaction is running.

这是说,A version change Transaction is running但据我所研究,版本更改事务是从IDBFactory.open方法,我没有使用,我已经指定此事务是readwrite,这个事务是在onupgradeneeded那么为什么会有错误？

我必须承认我对indexedDB很新

Answer 1

您需要在尝试加载对象存储之前检查版本更改事务是否完成：

request.onupgradeneeded =
    function(event) {
        db = event.target.result;
        var store = db.createObjectStore('Files', {keyPath:"files"});
        var transaction = event.target.transaction;

        transaction.oncomplete =
            function(event) {    
                // Now store is available to be populated
            }
    }

Answer 2

versionchange事务还允许您读写.您只需要在onupgradeneeded函数中访问为您创建的事务.

function go() {
  var req = indexeddb.open(...);
  req.onupgradeneeded = function(event) {

    // note that event.target === req === this, use whatever you like
    var db = event.target.result;

    // createObjectScore implicitly uses the versionchange txn running 
    // here, without telling you, basically a convenience function
    var objectStore = db.createObjectStore(...);

    // the important part that i am describing in this answer, 
    // grab the handle of the versionchange txn 
    // that is already running and was created for you
    // note again that event.target === req, you could just do
    // req.transaction or this.transaction here.
    // note this is a property of the open request, not a method. do NOT
    // confuse this with the method transaction() that is used to create a 
    // new transaction.
    var txn = event.target.transaction;

    // note that txn.objectStore(...) will work here, because the 
    // createObjectStore call earlier guarantees the store exists here
    // within the implicit upgrade txn
    var addRequest = txn.objectStore(...).add('value');

    // side note: if in previous line we did:
    // var objectStoreRetrievedFromTxn = txn.objectStore(...);
    // then that variable is equal to the same variable returned from 
    // db.createObjectStore earlier in this function. Both are simply handles 
    // (references, pointers, whatever you want to call it) to the store.

    // kind of dumb, but you could do this just to log something
    addRequest.onsuccess = function() {console.log('Success!');};
  };

  // called once upgrade txn completes (if it even needed to run), 
  // and db is opened
  req.onsuccess = function(event) {
    console.log('upgrade txn completed and db is now connected');
    // here, create whatever readwrite or readonly txns you want, note these 
    // txns are separate from and different than the versionchange txn from 
    // before, because that is a unique transaction only available within 
    // onupgradeneeded. however, both versionchange and readwrite are similar
    // in that both support calls to put or add
  };
}

您遇到错误,因为您在版本更改事务仍在运行时尝试启动第二个事务.