`TxoSpenderIndex` uses LevelDB values only as presence markers. `FindSpender` iterates over keys and loads the spending transaction from the disk position stored in each key.
Write new entries with a zero-byte span instead of a serialized empty string, so rebuilt indexes avoid one extra byte per spender entry.
Existing indexes remain readable because the lookup path does not deserialize the marker value.
`BaseIndex` currently uses the same name for logs, `getindexinfo`, prune locks, and the sync thread.
Linux truncates system thread names to 15 visible bytes after the `b-` prefix, so long indexer names are clipped in system tools.
Pass a separate thread name explicitly at each `BaseIndex` call site and shorten the OS-visible indexer names to `txidx`, `blkfltbscidx`, `coinstatsidx`, and `txospenderidx`.
Add an `Assume` to `ThreadRename()` so future OS-visible thread names keep fitting the same Linux limit.
The public index names, `getindexinfo` keys, command-line options, and on-disk paths stay unchanged.
Co-authored-by: winterrdog <winterrdog@users.noreply.github.com>
Co-authored-by: Hodlinator <172445034+hodlinator@users.noreply.github.com>
Co-authored-by: sedited <seb.kung@gmail.com>
Co-authored-by: MarcoFalke <*~=`'#}+{/-|&$^_@721217.xyz>
Adds an outpoint -> txid index, which can be used to find which transactions spent a given output.
We use a composite key with 2 parts (suggested by @romanz): hash(spent outpoint) and tx position, with an empty value.
To find the spending tx for a given outpoint, we do a prefix search (prefix being the hash of the provided outpoint), and for all keys that match this prefix
we load the tx at the position specified in the key and return it, along with the block hash, if does spend the provided outpoint.
To handle reorgs we just erase the keys computed from the removed block.
This index is extremely useful for Lightning and more generally for layer-2 protocols that rely on chains of unpublished transactions.
If enabled, this index will be used by `gettxspendingprevout` when it does not find a spending transaction in the mempool.
