Method BatchWrite

src/txdb.cpp:84–143

}

bool CCoinsViewDB::BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) {
    CDBBatch batch(db);
    size_t count = 0;
    size_t changed = 0;
    size_t batch_size = (size_t)gArgs.GetArg("-dbbatchsize", nDefaultDbBatchSize);
    int crash_simulate = gArgs.GetArg("-dbcrashratio", 0);
    assert(!hashBlock.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) {
            assert(old_heads[0] == hashBlock);
            old_tip = old_heads[1];
        }
    }

    // In the first batch, mark the database as being in the middle of a
    // transition from old_tip to hashBlock.
    // 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, std::vector<uint256>{hashBlock, old_tip});

    for (CCoinsMap::iterator it = mapCoins.begin(); it != mapCoins.end();) {
        if (it->second.flags & CCoinsCacheEntry::DIRTY) {
            CoinEntry entry(&it->first);
            if (it->second.coin.IsSpent())
                batch.Erase(entry);
            else
                batch.Write(entry, it->second.coin);
            changed++;
        }
        count++;
        CCoinsMap::iterator itOld = it++;
        mapCoins.erase(itOld);
        if (batch.SizeEstimate() > batch_size) {
            LogPrint(BCLog::COINDB, "Writing partial batch of %.2f MiB\n", batch.SizeEstimate() * (1.0 / 1048576.0));
            db.WriteBatch(batch);
            batch.Clear();
            if (crash_simulate) {
                static FastRandomContext rng;
                if (rng.randrange(crash_simulate) == 0) {
                    LogPrintf("Simulating a crash. Goodbye.\n");
                    _Exit(0);
                }
            }
        }
    }

    // In the last batch, mark the database as consistent with hashBlock again.
    batch.Erase(DB_HEAD_BLOCKS);
    batch.Write(DB_BEST_BLOCK, hashBlock);

    LogPrint(BCLog::COINDB, "Writing final batch of %.2f MiB\n", batch.SizeEstimate() * (1.0 / 1048576.0));
    bool ret = db.WriteBatch(batch);
    LogPrint(BCLog::COINDB, "Committed %u changed transaction outputs (out of %u) to coin database...\n", (unsigned int)changed, (unsigned int)count);