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 (IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
        return false;
    }
    {
        LOCK(cs_wallet);
        WalletBatch batch(*database);
        for (int64_t nIndex : setInternalKeyPool) {
            batch.ErasePool(nIndex);
        }
        setInternalKeyPool.clear();
        for (int64_t nIndex : setExternalKeyPool) {
            batch.ErasePool(nIndex);
        }
        setExternalKeyPool.clear();
        for (int64_t nIndex : set_pre_split_keypool) {
            batch.ErasePool(nIndex);
        }
        set_pre_split_keypool.clear();
        m_pool_key_to_index.clear();
        if (!TopUpKeyPool()) {
            return false;
        }
        LogPrintf("CWallet::NewKeyPool rewrote keypool\n");
    }
    return true;
}
size_t CWallet::KeypoolCountExternalKeys()