[IndexedDB] Adding txn, value, and key size metrics

content/browser/indexed_db/leveldb/leveldb_transaction.cc

Index: content/browser/indexed_db/leveldb/leveldb_transaction.cc
diff --git a/content/browser/indexed_db/leveldb/leveldb_transaction.cc b/content/browser/indexed_db/leveldb/leveldb_transaction.cc
index 252059f0ad415929d31a8be204790fa22564e216..0f939403b1e09de07eb2588ec1a2db3f96fbcc72 100644
--- a/content/browser/indexed_db/leveldb/leveldb_transaction.cc
+++ b/content/browser/indexed_db/leveldb/leveldb_transaction.cc
@@ -54,11 +54,14 @@ void LevelDBTransaction::Set(const StringPiece& key,
     record->key.assign(key.begin(), key.end() - key.begin());
     record->value.swap(*value);
     record->deleted = deleted;
+    size_ += sizeof(Record) + key.size() * 2 + value->size();

[pwnall, 2017/05/23 23:01:09]

This book-keeping looks subtle enough to require tests. Can you add some quick
unit tests today? If not, it seems fine to land this now and potentially fix
later.

FWIW, I was about to suggest the following plan, and my idea fell flat on its
face because LevelDB doesn't report WriteBatch size.

1) Forward the WriteBatch size getter in LevelDBWriteBatch --
https://cs.chromium.org/chromium/src/content/browser/indexed_db/leveldb/level...

2) Change LevelDBTransaction::Commit to return the WriteBatch size in an
out-parameter --
https://cs.chromium.org/chromium/src/content/browser/indexed_db/leveldb/level...

3) Log the value in IndexedDBBackingStore::Transaction::CommitPhaseTwo
--https://cs.chromium.org/chromium/src/content/browser/indexed_db/indexed_db_backing_store.cc?l=4242

[dmurph, 2017/05/24 02:01:58]

BAsed on our convo, recording right before the journal commit, and I'll follow
up with blob metrics in a new CL.

     data_[record->key] = std::move(record);
     NotifyIterators();
     return;
   }
+  size_ += value->size();
   it->second->value.swap(*value);
+  size_ -= value->size();
   it->second->deleted = deleted;
 }
 
@@ -375,10 +378,12 @@ void LevelDBTransaction::TransactionIterator::Delete() {
   DCHECK(IsValid());
   if (current_ == data_iterator_.get()) {
     data_iterator_->Delete();
+    transaction_->size_ -= data_iterator_->Value().size();

[pwnall, 2017/05/23 23:01:10]

IIUC, this removes the record from the map, so I think you need to subtract
sizeof(Record) + key.size() * 2 + value->size().

[dmurph, 2017/05/24 02:01:58]

Added tests. Offline convo - record isn't removed from map, just the value.

   } else {
     std::unique_ptr<Record> record = base::MakeUnique<Record>();
     record->key = Key().as_string();
     record->deleted = true;
+    transaction_->size_ += sizeof(Record) + record->key.size() * 2;
     transaction_->data_[record->key] = std::move(record);
   }
 }