This commit prunes several unused functions from the Db interface and the
underlying implementations. For the most part these are holdovers from
the original sqlite implementation. It also removes the types associated
with those functions since they are no longer needed. The following
functions and types have been removed:
- InvalidateCache
- InvalidateBlockCache
- InvalidateTxCache
- SetDBInsertMode
- InsertMode type and associated constants
- NewIterateBlocks
- BlockIterator interface
The reasons for removing these are broken out below.
- Neither of two current implementations implement these functions nor
does any of the fully functional code using the interface invoke them.
- After contemplating and testing caching of blocks and transactions at
this layer, it doesn't seem to provide any real benefit unless very
specific assumptions about the use case are made. Making those
assumptions can make other use cases worse. For example, assuming a
large cache is harmful to memory-constrained use cases. Leaving it up
to the caller to choose when to cache block and transactions allows much
greater flexibility.
- The DB insert mode was an artifact of the original sqlite implementation
and probably should have only been exposed specifically on the
implementation as opposed through generic interface. If a specific
implementation wishes to provide functionality such as special modes,
that should be done through type assertions.
This commit introduces two new functions to the btcdb.Db interface named
FetchBlockHeightBySha and FetchBlockHeaderBySha.
The FetchBlockHeightBySha function is useful since previously it was only
possible to get the height of block by fetching the entire block with
FetchBlockBySha and pulling the height out of the returned btcutil.Block.
The FetchBlockHeaderBySha function will ultimately make it much more
efficient to fetch block headers. Currently, due to the database design
in the ldb backend, the entire block has to be loaded anyways, so the only
current benefit is to avoid the deserialize on all of the transactions.
However, ultimately btcdb will gain a more efficient backend which can
also avoid reading all of the extra transaction data altogether.
This commit adds a new backend driver which conforms to the btcdb
interface to provide a memory only database. This is primarily useful for
testing purposes as normal operations require a persistent block storage
mechanism.
