Files
bitcoin/doc
merge-script c90c23d388 Merge bitcoin/bitcoin#35531: txindex: hash keys and pack positions to reduce disk usage
25bed560be test: add forward-compat functional test for txindex (sedited)
703304ed8c doc: add release notes for txindex disk usage and downgrading (Andrew Toth)
8e5320a2d2 tests: cover txindex hash prefix collisions and legacy fallback (Andrew Toth)
b75efa19ba txindex: skip bloom filters and legacy lookups for new databases (Andrew Toth)
004d7c098c txindex: hash key prefixes and pack block positions (Andrew Toth)
5a255970fd refactor: move txindex db constants and legacy key to txindex_key.h (Andrew Toth)
327660134c txindex: pass the full block to DB::WriteTxs (Andrew Toth)
42771e7998 txindex: use a new block locator for downgrade safety (Andrew Toth)
4b08baed72 txindex: return optional tx and block hash from FindTx (Andrew Toth)

Pull request description:

  The current txindex uses the full 32-byte txid as keys, which takes up about 66 GB of disk space today on mainnet. Using a 5-byte key prefix instead drops the disk usage to 26 GB - cutting the size to less than half.

  Using the full 32-bytes is unnecessary since a 5-byte salted siphash will produce collisions in about 1 in 1.1 trillion. Some collisions will occur, but the penalty is just an extra disk read, deserialization and hash.
  The tx position can be appended to the key instead of used as a value, and a LevelDB iterator can seek to the prefix and then scan for the correct tx. This is an almost identical approach to `txospenderindex`.

  Also instead of storing the file position of the block, we can store only the sequence of the connected block and offset of the transaction in the block. This can be packed into a 6-byte key suffix using 3-byte representations of the sequence and offset in the block. The block file can be recovered by the CBlockIndex that is already in memory. The sequence is mapped to the block hash in the db, so we can lookup the block hash to find the CBlockIndex during reads.

  If a tx is not found with this method, we fallback to looking up the legacy entry. With this method a user with an existing db can opt to erase the `indexes/txindex` folder and reindex, or keep the current index and new entries will be appended with the smaller footprint.

  The time to index was faster on my machine with this method, 1h19m vs current 1h50m.
  Lookups are roughly the same, around 0.2ms per lookup with `getrawtransaction`.
  When testing on mainnet, I got 894,549 2-way collisions, 395 3-way collision, and 1 4-way collision that worst case could cause an extra 3 false positives when reading.

ACKs for top commit:
  l0rinc:
    diff reACK 25bed560be
  sedited:
    ACK 25bed560be
  ajtowns:
    ACK 25bed560be

Tree-SHA512: a25c79ca7e722e2f372b65f5fc11c8b194ad49f2240b4881c7e606306aabbd3604aede3f1c33606b467486affac3a3f503638f513c896935cebbc02709cb60d8
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Bitcoin Core

Setup

Bitcoin Core is the original Bitcoin client and it builds the backbone of the network. It downloads and, by default, stores the entire history of Bitcoin transactions, which requires several hundred gigabytes or more of disk space. Depending on the speed of your computer and network connection, the synchronization process can take anywhere from a few hours to several days or more.

To download Bitcoin Core, visit bitcoincore.org.

Running

The following are some helpful notes on how to run Bitcoin Core on your native platform.

Unix

Unpack the files into a directory and run:

  • bin/bitcoin-qt (GUI) or
  • bin/bitcoind (headless)
  • bin/bitcoin (wrapper command)

The bitcoin command supports subcommands like bitcoin gui, bitcoin node, and bitcoin rpc exposing different functionality. Subcommands can be listed with bitcoin help.

Windows

Unpack the files into a directory, and then run bitcoin-qt.exe.

macOS

Drag Bitcoin Core to your applications folder, and then run Bitcoin Core.

Need Help?

Building

The following are developer notes on how to build Bitcoin Core on your native platform. They are not complete guides, but include notes on the necessary libraries, compile flags, etc.

Development

The Bitcoin repo's root README contains relevant information on the development process and automated testing.

Resources

Miscellaneous

License

Distributed under the MIT software license.