IndexedDB: Defer delete calls when there is a running upgrade

content/browser/indexed_db/indexed_db_database.cc

Index: content/browser/indexed_db/indexed_db_database.cc
diff --git a/content/browser/indexed_db/indexed_db_database.cc b/content/browser/indexed_db/indexed_db_database.cc
index 97f47a04d14cd726d5f86b16f2b6c7a9502a7995..caa39cba7db71e5b50353b952ed9e12bb6b204c6 100644
--- a/content/browser/indexed_db/indexed_db_database.cc
+++ b/content/browser/indexed_db/indexed_db_database.cc
@@ -233,6 +233,7 @@ IndexedDBDatabase::~IndexedDBDatabase() {
   DCHECK(transactions_.empty());
   DCHECK(pending_open_calls_.empty());
   DCHECK(pending_delete_calls_.empty());
+  DCHECK(blocked_delete_calls_.empty());
 }
 
 size_t IndexedDBDatabase::GetMaxMessageSizeInBytes() const {
@@ -1600,7 +1601,7 @@ size_t IndexedDBDatabase::RunningUpgradeCount() const {
 }
 
 size_t IndexedDBDatabase::PendingDeleteCount() const {
-  return pending_delete_calls_.size();
+  return pending_delete_calls_.size() + blocked_delete_calls_.size();
 }
 
 void IndexedDBDatabase::ProcessPendingCalls() {
@@ -1616,31 +1617,58 @@ void IndexedDBDatabase::ProcessPendingCalls() {
     DCHECK_EQ(1u, ConnectionCount());
     // Fall through would be a no-op, since transaction must complete
     // asynchronously.
+    DCHECK(IsUpgradeRunning());
     DCHECK(IsDeleteDatabaseBlocked());
     DCHECK(IsOpenConnectionBlocked());
     return;
   }
 
-  if (!IsDeleteDatabaseBlocked()) {
+  if (IsUpgradeRunning()) {
+    DCHECK_EQ(ConnectionCount(), 1UL);
+    return;
+  }
+
+  // These delete calls were blocked by a running upgrade, and did not even
+  // get as far as broadcasting OnVersionChange (if needed).
+  {
     PendingDeleteCallList pending_delete_calls;
     pending_delete_calls_.swap(pending_delete_calls);
     while (!pending_delete_calls.empty()) {
-      // Only the first delete call will delete the database, but each must fire
-      // callbacks.
       std::unique_ptr<PendingDeleteCall> pending_delete_call(
           pending_delete_calls.front());
       pending_delete_calls.pop_front();
-      DeleteDatabaseFinal(pending_delete_call->callbacks());
+      DeleteDatabase(pending_delete_call->callbacks());
     }
-    // delete_database_final should never re-queue calls.
+    // DeleteDatabase should never re-queue these calls.
     DCHECK(pending_delete_calls_.empty());
+    // Fall through when complete, as pending deletes/opens may be unblocked.
+  }
+
+  // These delete calls broadcast OnVersionChange (if needed) but were blocked
+  // by open connections.
+  if (!IsDeleteDatabaseBlocked()) {
+    PendingDeleteCallList blocked_delete_calls;
+    blocked_delete_calls_.swap(blocked_delete_calls);
+    while (!blocked_delete_calls.empty()) {
+      // Only the first delete call will delete the database, but each must fire
+      // callbacks.
+      std::unique_ptr<PendingDeleteCall> pending_delete_call(
+          blocked_delete_calls.front());
+      blocked_delete_calls.pop_front();
+      DeleteDatabaseFinal(pending_delete_call->callbacks());
+    }
+    // DeleteDatabaseFinal should never re-queue these calls.
+    DCHECK(blocked_delete_calls_.empty());
     // Fall through when complete, as pending opens may be unblocked.
   }
 
+  // These open calls were blocked by a pending/running upgrade or a pending
+  // delete.
   if (!IsOpenConnectionBlocked()) {
     PendingOpenCallList pending_open_calls;
     pending_open_calls_.swap(pending_open_calls);
     while (!pending_open_calls.empty()) {
+      // This may re-queue open calls if an upgrade is necessary.
       OpenConnection(pending_open_calls.front());
       pending_open_calls.pop_front();
     }
@@ -1674,18 +1702,22 @@ void IndexedDBDatabase::TransactionCreated(IndexedDBTransaction* transaction) {
   transactions_[transaction->id()] = transaction;
 }
 
+bool IndexedDBDatabase::IsUpgradeRunning() const {
+  return transaction_coordinator_.IsRunningVersionChangeTransaction();
+}
+
+bool IndexedDBDatabase::IsUpgradePendingOrRunning() const {
+  return pending_run_version_change_transaction_call_ || IsUpgradeRunning();
+}
+
 bool IndexedDBDatabase::IsOpenConnectionBlocked() const {
-  return !pending_delete_calls_.empty() ||
-         transaction_coordinator_.IsRunningVersionChangeTransaction() ||
-         pending_run_version_change_transaction_call_;
+  return IsUpgradePendingOrRunning() || !blocked_delete_calls_.empty();

[cmumford, 2016/06/23 21:44:19]

nit: blocked_delete_calls_.empty() is constant time and faster - check it first?

[jsbell, 2016/06/23 22:26:50]

IsUpgradePendingOrRunning() should be constant time too - at most one
transaction needs to be checked for IsUpgradeRunning().

But yeah, I can flip it.

 }
 
 void IndexedDBDatabase::OpenConnection(
     const IndexedDBPendingConnection& connection) {
   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
@@ -1812,6 +1844,7 @@ void IndexedDBDatabase::RunVersionChangeTransactionFinal(
                     object_store_ids,
                     blink::WebIDBTransactionModeVersionChange);
 
+  DCHECK(transaction_coordinator_.IsRunningVersionChangeTransaction());
   transactions_[transaction_id]->ScheduleTask(
       base::Bind(&IndexedDBDatabase::VersionChangeOperation,
                  this,
@@ -1823,6 +1856,12 @@ void IndexedDBDatabase::RunVersionChangeTransactionFinal(
 
 void IndexedDBDatabase::DeleteDatabase(
     scoped_refptr<IndexedDBCallbacks> callbacks) {
+  // If there's a running upgrade, the delete calls should be deferred so that
+  // "versionchange" is seen after "success" fires.
+  if (IsUpgradeRunning()) {
+    pending_delete_calls_.push_back(new PendingDeleteCall(callbacks));
+    return;
+  }
 
   if (IsDeleteDatabaseBlocked()) {
     for (const auto* connection : connections_) {
@@ -1834,14 +1873,14 @@ void IndexedDBDatabase::DeleteDatabase(
     // OnBlocked will be fired at the request when one of the other
     // connections acks that the OnVersionChange was ignored.
 
-    pending_delete_calls_.push_back(new PendingDeleteCall(callbacks));
+    blocked_delete_calls_.push_back(new PendingDeleteCall(callbacks));
     return;
   }
   DeleteDatabaseFinal(callbacks);
 }
 
 bool IndexedDBDatabase::IsDeleteDatabaseBlocked() const {
-  return !!ConnectionCount();
+  return IsUpgradePendingOrRunning() || !!ConnectionCount();
 }
 
 void IndexedDBDatabase::DeleteDatabaseFinal(
@@ -1880,15 +1919,15 @@ void IndexedDBDatabase::ForceClose() {
 }
 
 void IndexedDBDatabase::VersionChangeIgnored() {
-  if (pending_run_version_change_transaction_call_)
+  if (pending_run_version_change_transaction_call_) {
     pending_run_version_change_transaction_call_->callbacks()->OnBlocked(
         metadata_.version);
+  }
 
-  for (const auto& pending_delete_call : pending_delete_calls_)
+  for (const auto& pending_delete_call : blocked_delete_calls_)
     pending_delete_call->callbacks()->OnBlocked(metadata_.version);
 }
 
-
 void IndexedDBDatabase::Close(IndexedDBConnection* connection, bool forced) {
   DCHECK(connections_.count(connection));
   DCHECK(connection->IsConnected());
@@ -1924,7 +1963,7 @@ void IndexedDBDatabase::Close(IndexedDBConnection* connection, bool forced) {
 
   // TODO(jsbell): Add a test for the pending_open_calls_ cases below.
   if (!ConnectionCount() && !pending_open_calls_.size() &&
-      !pending_delete_calls_.size()) {
+      !blocked_delete_calls_.size()) {

[cmumford, 2016/06/23 21:44:19]

Nit: I know you're sticking with existing pattern, but
blocked_delete_calls_.empty() is more readable, and std::list::size() might not
be constant time.

[jsbell, 2016/06/23 22:26:50]

Whoops, yeah, I'll use empty(). That was ported from webkit code. :P

(std::list::size() is apparently constant since C++11)

     DCHECK(transactions_.empty());
     backing_store_ = NULL;
     factory_->ReleaseDatabase(identifier_, forced);