Method BatchWrite

src/txdb.cpp:122–186

}

void CCoinsViewDB::BatchWrite(CoinsViewCacheCursor& cursor, const uint256& block_hash)
{
    CDBBatch batch(*m_db);
    size_t count = 0;
    const size_t dirty_count{cursor.GetDirtyCount()};
    assert(!block_hash.IsNull());

    uint256 old_tip = GetBestBlock();
    if (old_tip.IsNull()) {
        // We may be in the middle of replaying.
        std::vector<uint256> old_heads = GetHeadBlocks();
        if (old_heads.size() == 2) {
            if (old_heads[0] != block_hash) {
                LogError("The coins database detected an inconsistent state, likely due to a previous crash or shutdown. You will need to restart bitcoind with the -reindex-chainstate or -reindex configuration option.\n");
            }
            assert(old_heads[0] == block_hash);
            old_tip = old_heads[1];
        }
    }

    if (dirty_count > WARN_FLUSH_COINS_COUNT) LogWarning("Flushing large (%d entries) UTXO set to disk, it may take several minutes", dirty_count);
    LOG_TIME_MILLIS_WITH_CATEGORY(strprintf("write coins cache to disk (%d out of %d cached coins)",
        dirty_count, cursor.GetTotalCount()), BCLog::BENCH);

    // In the first batch, mark the database as being in the middle of a
    // transition from old_tip to block_hash.
    // A vector is used for future extensibility, as we may want to support
    // interrupting after partial writes from multiple independent reorgs.
    batch.Erase(DB_BEST_BLOCK);
    batch.Write(DB_HEAD_BLOCKS, Vector(block_hash, old_tip));

    for (auto it{cursor.Begin()}; it != cursor.End();) {
        if (it->second.IsDirty()) {
            CoinEntry entry(&it->first);
            if (it->second.coin.IsSpent()) {
                batch.Erase(entry);
            } else {
                batch.Write(entry, it->second.coin);
            }
        }
        count++;
        it = cursor.NextAndMaybeErase(*it);
        if (batch.ApproximateSize() > m_options.batch_write_bytes) {
            LogDebug(BCLog::COINDB, "Writing partial batch of %.2f MiB\n", batch.ApproximateSize() / double(1_MiB));

            m_db->WriteBatch(batch);
            batch.Clear();
            if (m_options.simulate_crash_ratio) {
                static FastRandomContext rng;
                if (rng.randrange(m_options.simulate_crash_ratio) == 0) {
                    LogError("Simulating a crash. Goodbye.");
                    _Exit(0);
                }
            }
        }
    }

    // In the last batch, mark the database as consistent with block_hash again.