Tell IDB frontend about data loss

content/browser/indexed_db/indexed_db_database.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/indexed_db/indexed_db_database.h"
 
 #include <math.h>
 #include <vector>
 
 #include "base/auto_reset.h"
@@ skipping 45 matching lines @@
 };
 
 class IndexedDBDatabase::VersionChangeOperation
     : public IndexedDBTransaction::Operation {
  public:
   VersionChangeOperation(
       scoped_refptr<IndexedDBDatabase> database,
       int64 transaction_id,
       int64 version,
       scoped_refptr<IndexedDBCallbacksWrapper> callbacks,
-      scoped_refptr<IndexedDBDatabaseCallbacksWrapper> database_callbacks)
+      scoped_refptr<IndexedDBDatabaseCallbacksWrapper> database_callbacks,
+      bool data_loss)

[jsbell, 2013/06/14 20:42:58]

Pluming this through VersionChangeOperation seems odd at first glance, although
it makes sense if you follow the flow of the flag through the system.

Some alternatives that come to mind.
* Have it be a state on database, i.e. "when opened, there was some data loss".
I guess it would need to be reset after being plucked out so only the first
connection would see it.
* Have it be a state on the backing store itself, i.e. "when opened, there was
some data loss". This would let us signal each subsequent database open that
there was data loss, but then every database would get it until all handles were
closed, unless we added even more state tracking. :(

I don't think either of those are better than what's here, though.

[dgrogan, 2013/06/14 22:06:43]

I considered keeping some state like you describe but also didn't like any of
the options. Shrug.

       : database_(database),
         transaction_id_(transaction_id),
         version_(version),
         callbacks_(callbacks),
-        database_callbacks_(database_callbacks) {}
+        database_callbacks_(database_callbacks),
+        data_loss_(data_loss) {}
   virtual void Perform(IndexedDBTransaction* transaction) OVERRIDE;
 
  private:
   scoped_refptr<IndexedDBDatabase> database_;
   int64 transaction_id_;
   int64 version_;
   scoped_refptr<IndexedDBCallbacksWrapper> callbacks_;
   scoped_refptr<IndexedDBDatabaseCallbacksWrapper> database_callbacks_;
+  bool data_loss_;
 };
 
 class CreateObjectStoreAbortOperation : public IndexedDBTransaction::Operation {
  public:
   CreateObjectStoreAbortOperation(scoped_refptr<IndexedDBDatabase> database,
                                   int64 object_store_id)
       : database_(database), object_store_id_(object_store_id) {}
   virtual void Perform(IndexedDBTransaction* transaction) OVERRIDE;
 
  private:
@@ skipping 1297 matching lines @@
         WebKit::WebIDBDatabaseExceptionUnknownError,
         ASCIIToUTF16("Internal error writing data to stable storage when "
                      "updating version."));
     callbacks_->OnError(error);
     transaction->Abort(error);
     return;
   }
   DCHECK(!database_->pending_second_half_open_);
   database_->pending_second_half_open_.reset(new PendingOpenCall(
       callbacks_, database_callbacks_, transaction_id_, version_));
-  callbacks_->OnUpgradeNeeded(old_version, database_, database_->metadata());
+  callbacks_->OnUpgradeNeeded(
+      old_version, database_, database_->metadata(), data_loss_);
 }
 
 void IndexedDBDatabase::TransactionStarted(IndexedDBTransaction* transaction) {
 
   if (transaction->mode() == indexed_db::TRANSACTION_VERSION_CHANGE) {
     DCHECK(!running_version_change_transaction_);
     running_version_change_transaction_ = transaction;
   }
 }
 
@@ skipping 52 matching lines @@
   }
 
   if (pending_run_version_change_transaction_call_ && ConnectionCount() == 1) {
     DCHECK(pending_run_version_change_transaction_call_->Version() >
            metadata_.int_version);
     scoped_ptr<PendingOpenCall> pending_call =
         pending_run_version_change_transaction_call_.Pass();
     RunVersionChangeTransactionFinal(pending_call->Callbacks(),
                                      pending_call->DatabaseCallbacks(),
                                      pending_call->TransactionId(),
-                                     pending_call->Version());
+                                     pending_call->Version(),
+                                     false);

[jsbell, 2013/06/14 20:42:58]

Can you give the argument a default value instead of passing explicit false in
these cases?

[dgrogan, 2013/06/14 22:06:43]

Done.

     DCHECK_EQ(static_cast<size_t>(1), ConnectionCount());
     // Fall through would be a no-op, since transaction must complete
     // asynchronously.
     DCHECK(IsDeleteDatabaseBlocked());
     DCHECK(IsOpenConnectionBlocked());
     return;
   }
 
   if (!IsDeleteDatabaseBlocked()) {
     PendingDeleteCallList pending_delete_calls;
@@ skipping 13 matching lines @@
 
   if (!IsOpenConnectionBlocked()) {
     PendingOpenCallList pending_open_calls;
     pending_open_calls_.swap(pending_open_calls);
     while (!pending_open_calls.empty()) {
       scoped_ptr<PendingOpenCall> pending_open_call(pending_open_calls.front());
       pending_open_calls.pop_front();
       OpenConnection(pending_open_call->Callbacks(),
                      pending_open_call->DatabaseCallbacks(),
                      pending_open_call->TransactionId(),
-                     pending_open_call->Version());
+                     pending_open_call->Version(),
+                     false);

[jsbell, 2013/06/14 20:42:58]

Ditto.

[dgrogan, 2013/06/14 22:06:43]

Done.

     }
   }
 }
 
 void IndexedDBDatabase::CreateTransaction(
     int64 transaction_id,
     scoped_refptr<IndexedDBDatabaseCallbacksWrapper> callbacks,
     const std::vector<int64>& object_store_ids,
     uint16 mode) {
 
@@ skipping 13 matching lines @@
 bool IndexedDBDatabase::IsOpenConnectionBlocked() const {
   return !pending_delete_calls_.empty() ||
          running_version_change_transaction_ ||
          pending_run_version_change_transaction_call_;
 }
 
 void IndexedDBDatabase::OpenConnection(
     scoped_refptr<IndexedDBCallbacksWrapper> callbacks,
     scoped_refptr<IndexedDBDatabaseCallbacksWrapper> database_callbacks,
     int64 transaction_id,
-    int64 version) {
+    int64 version,
+    bool data_loss) {
   DCHECK(backing_store_.get());
 
   // TODO(jsbell): Should have a priority queue so that higher version
   // requests are processed first. http://crbug.com/225850
   if (IsOpenConnectionBlocked()) {
+    // The backing store only detects data loss when it is first opened. The
+    // presence of existing connections means we didn't even check for data loss
+    // so there'd better not be any.
+    DCHECK(!data_loss);
     pending_open_calls_.push_back(new PendingOpenCall(
         callbacks, database_callbacks, transaction_id, version));
     return;
   }
 
   if (metadata_.id == kInvalidId) {
     // The database was deleted then immediately re-opened; OpenInternal()
     // recreates it in the backing store.
     if (OpenInternal()) {
       DCHECK_EQ(metadata_.int_version,
@@ skipping 36 matching lines @@
       return;
     }
     // Spec says: If no version is specified and no database exists, set
     // database version to 1.
     version = 1;
   }
 
   if (version > metadata_.int_version) {
     database_callbacks_set_.insert(database_callbacks);
     RunVersionChangeTransaction(
-        callbacks, database_callbacks, transaction_id, version);
+        callbacks, database_callbacks, transaction_id, version, data_loss);
     return;
   }
   if (version < metadata_.int_version) {
     callbacks->OnError(IndexedDBDatabaseError(
         WebKit::WebIDBDatabaseExceptionVersionError,
         ASCIIToUTF16("The requested version (") + Int64ToString16(version) +
             ASCIIToUTF16(") is less than the existing version (") +
             Int64ToString16(metadata_.int_version) + ASCIIToUTF16(").")));
     return;
   }
   DCHECK_EQ(version, metadata_.int_version);
   database_callbacks_set_.insert(database_callbacks);
   callbacks->OnSuccess(this, this->metadata());
 }
 
 void IndexedDBDatabase::RunVersionChangeTransaction(
     scoped_refptr<IndexedDBCallbacksWrapper> callbacks,
     scoped_refptr<IndexedDBDatabaseCallbacksWrapper> database_callbacks,
     int64 transaction_id,
-    int64 requested_version) {
+    int64 requested_version,
+    bool data_loss) {
 
   DCHECK(callbacks.get());
   DCHECK(database_callbacks_set_.has(database_callbacks));
   if (ConnectionCount() > 1) {
+    DCHECK(!data_loss);
     // Front end ensures the event is not fired at connections that have
     // close_pending set.
     for (DatabaseCallbacksSet::const_iterator it =
              database_callbacks_set_.begin();
          it != database_callbacks_set_.end();
          ++it) {
       if (it->get() != database_callbacks.get())
         (*it)->OnVersionChange(metadata_.int_version, requested_version);
     }
     // TODO(jsbell): Remove the call to on_blocked and instead wait
     // until the frontend tells us that all the "versionchange" events
     // have been delivered.  http://crbug.com/100123
     callbacks->OnBlocked(metadata_.int_version);
 
     DCHECK(!pending_run_version_change_transaction_call_);
     pending_run_version_change_transaction_call_.reset(new PendingOpenCall(
         callbacks, database_callbacks, transaction_id, requested_version));
     return;
   }
-  RunVersionChangeTransactionFinal(
-      callbacks, database_callbacks, transaction_id, requested_version);
+  RunVersionChangeTransactionFinal(callbacks,
+                                   database_callbacks,
+                                   transaction_id,
+                                   requested_version,
+                                   data_loss);
 }
 
 void IndexedDBDatabase::RunVersionChangeTransactionFinal(
     scoped_refptr<IndexedDBCallbacksWrapper> callbacks,
     scoped_refptr<IndexedDBDatabaseCallbacksWrapper> database_callbacks,
     int64 transaction_id,
-    int64 requested_version) {
+    int64 requested_version,
+    bool data_loss) {
 
   std::vector<int64> object_store_ids;
   CreateTransaction(transaction_id,
                     database_callbacks,
                     object_store_ids,
                     indexed_db::TRANSACTION_VERSION_CHANGE);
   scoped_refptr<IndexedDBTransaction> transaction =
       transactions_[transaction_id];
 
   transaction->ScheduleTask(
       new VersionChangeOperation(this,
                                  transaction_id,
                                  requested_version,
                                  callbacks,
-                                 database_callbacks),
+                                 database_callbacks,
+                                 data_loss),
       new VersionChangeAbortOperation(
           this, metadata_.version, metadata_.int_version));
 
   DCHECK(!pending_second_half_open_);
 }
 
 void IndexedDBDatabase::DeleteDatabase(
     scoped_refptr<IndexedDBCallbacksWrapper> callbacks) {
 
   if (IsDeleteDatabaseBlocked()) {
@@ skipping 110 matching lines @@
 
 void IndexedDBDatabase::VersionChangeAbortOperation::Perform(
     IndexedDBTransaction* transaction) {
   IDB_TRACE("VersionChangeAbortOperation");
   DCHECK(!transaction);
   database_->metadata_.version = previous_version_;
   database_->metadata_.int_version = previous_int_version_;
 }
 
 }  // namespace content