. - Issue - bitcoin/bitcoin

(EDITED)

List of implementation changes:

new database layout:
- 2 leveldb's (coins/ and blktree/ subdirs), replacing blkindex.dat
- separate directory (blocks/) with block data (in the usual format, but smaller files) and undo data
database keys are of the form (char,key) instead of (string,key) for reasons of compactness
there is no txid-to-diskpos index anymore, only blkid-to-diskpos and txid-to-unspent-outputs
- this makes getrawtransaction only work on unspent outputs (and slower)
  - an optional txid-to-diskpos index is planned
some new very specialized serializers are added (compact variable-length integer, compact amount, compact txout)
block index does not store hashBlockNext anymore - this is reconstructed from hashBestBlock at startup
at startup, automatically reorg to the best block in blktree/blocks
new RPCs: gettxoutsetinfo and gettxout operate on the coins database
no more CTxIndex in-scope: instead, a global pcoinsTip (representing the coin db) and pblocktree (representing the blktree db)
- intended to be moved to separate modules/classes, properly encapsulated
blktree database contains statistics about the block file (size, which blocks in it, times, heights, undo stats, ...)
blktree database contains flag per block that determines the degree of validation it had, to allow future headers-first mode
block files are pre-allocated (in batches of 16 MiB, the files grow to max 128 MIB), to reduce fragmentation
transaction hashes are cached, and typically never calculated more than once

Included in the pullreq, but technically separate:

Originally posted by @sipa in #1677 (comment)

Hello, is there any formula or performance tests to choose the size of 128 MB as chunksize in blk*.data files?