This commit modifies the code to make use of the new btcd APIs that allow
fetching of transaction lists which either do or do not include fully
spent transactions. It is more efficient to avoid fetching fully spent
transactions from the database when they aren't needed.
This commit adds a quick check to the transaction store fetch code which
simply returns an empty store if no hashes were requested rather than
bothering the db with an empty list.
This commit modifies the transaction lookup code to use a set instead of a
slice (list). This allows the lookup to automatically prevent duplicate
requests to the database.
Previously, the code simply added every referenced transaction to a list
without checking for duplicates, which led to multiple requests against
the database for the same transaction. It also meant the request list
could grow quite large with all of the duplicates using far more memory
than required.
While the end result was accurate, operating that way is not as efficient
as only requesting unique transactions.
Several of the functions require a map of contextual transaction data to
use as a source for referenced transactions. This commit exports the
underlying TxData type and creates a new type TxStore, which is a map of
points to the under TxData. In addition, this commit exposes a new
function, FetchTransactionStore, which returns a transaction store
(TxStore) containing all of the transactions referenced by the passed
transaction, as well as the existing transaction if it already exists.
This paves the way for subsequent commits which will expose some of the
functions which depend on this transaction store.
This commit modifies the code to choose sane defaults for the backing
arrays for slices that involve a lot of appends such block locators, hash
processing, and needed transactions. This is an optimization to avoid
the overhead of growing the backing arrays and copying the data multiple
times in the most common case. This also prevents a leak in Go GC which
will likely ultimatley be fixed, but the efficiecy gains alone are worth
the change.
Rather than removing disconnected transactions from the node viewpoint
transaction store, clear the entry instead. This is needed for the
connect code to update transactions that were removed on the other side of
a chain fork.
This commit updates the calls into btcutil, btcscript, and btcwire for the
latest API changes which remove the need for the protocol version for
serialization and deserialization of blocks and transactions.
It is acceptable for a transaction input in a block to reference the
output of another transaction in the same block only if the referenced
transaction comes before the transaction referencing it.
