Crate melblkidx

Block indexer for Melscan (and possibly more)

The block indexer pulls blocks from the network one by one using a Client and indexes them.

SQLite schema overview

coins table

The main data structure is a SQLite table that tracks the state of all coins seen with the following columns:

• create_txhash: hash of the creating transaction
• create_index: index at the creating transaction (e.g. which output was it)
• create_height: height of the creating transaction
• spend_txhash: hash of the spending transaction
• spend_index: index at the spending transaction (e.g. which input was it)
• spend_height: height of the spending transaction
• value: value being spent (big-endian blob)
• denom: denomination (blob)
• covhash: address (string)
• additional_data: (blob)

The spending information is denormalized into this table to improve the performance of e.g. balance queries (“which coins were created”)

“Tricky” cases (Melswap transactions, mostly) are handled by actually asking for more information from the network, rather than by reimplementating all the nuances of the state transition function. This is a big reason why we use a pull-based rather than an I/O-free, push-based API.

headvars table

• height
• blkhash
• fee_pool
• fee_multiplier
• dosc_speed

stakes table

stores all stakedocs ever, which is all we really need

• txhash
• pubkey
• e_start
• e_post_end
• staked

txvars table

• txhash
• kind
• fee
• covenants (JSON)
• data
• sigs (JSON)

Query API

Query facts about coins

// iterator over all coins with value above 100 µMEL
let i: impl Iterator<Item = CoinInfo> =
    indexer.query_coins()
        .value_range(CoinValue(100)..)
        .denom(Denom::Mel)
        .iter()

pub struct CoinInfo {
    pub create_txhash: TxHash,
    pub create_index: u8,
    pub create_height: BlockHeight,
    pub coin_data: CoinData,
    pub spend_info: Option<CoinSpendInfo>
}

pub struct CoinSpendInfo {
    pub spend_txhash: TxHash,
    pub spend_index: u8,
    pub spend_height: BlockHeight
}

Structs

• BalanceTracker
  Tracks the balance (sum of values) of all coins fulfilling some condition specified by the given CoinQuery, that are alive at a given height. Intelligently caches and plans around previous queries to avoid scanning all coins.
• CoinInfo
  Info about a coin.
• CoinQuery
  A half-built query on the coins table
• CoinSpendInfo
  Info about how the coin was spent.
• HeightInfo
  Miscellenous info about height
• Indexer
  An asynchronous Melodeon block indexer.