In the log I see things like:

    2017-09-13 03:54:33 init message: Rescanning...
    2017-09-13 03:54:33 Rescanning last 68616 blocks (from block 416339)...
    2017-09-13 03:54:40 AddToWallet xxxxx  update
    2017-09-13 03:55:33 Still rescanning. At block 418849. Progress=0.549138

I would be interested to see the wallet file name on each of these log lines.

Would there be any interest in merging such a PR?
{
    if (!EraseIC(std::make_pair(std::string("watchmeta"), dest))) {
        return false;
    }
    return EraseIC(std::make_pair(std::string("watchs"), dest));
}
bool WalletBatch::WriteBestBlock(const CBlockLocator& locator)
{
    WriteIC(std::string("bestblock"), CBlockLocator()); 
    return WriteIC(std::string("bestblock_nomerkle"), locator);
}
bool WalletBatch::ReadBestBlock(CBlockLocator& locator)
{
    if (m_batch.Read(std::string("bestblock"), locator) && !locator.vHave.empty()) return true;
    return m_batch.Read(std::string("bestblock_nomerkle"), locator);
}
bool WalletBatch::WriteOrderPosNext(int64_t nOrderPosNext)
{
    return WriteIC(std::string("orderposnext"), nOrderPosNext);
}
bool WalletBatch::ReadPool(int64_t nPool, CKeyPool& keypool)
{
    return m_batch.Read(std::make_pair(std::string("pool"), nPool), keypool);
}
bool WalletBatch::WritePool(int64_t nPool, const CKeyPool& keypool)