Move the txid duplicates check into BuildMerkleTree, where it can be done
much more efficiently (without needing to build a full txid set to detect
duplicates).
The previous version (using the std::set<uint256> to detect duplicates) was
also slightly too weak. A block mined with actual duplicate transactions
(which is invalid, due to the inputs of the duplicated transactions being
seen as double spends) would trigger the duplicates logic, resulting in the
block not being stored on disk, and rerequested. This change fixes that by
only triggering in the case of duplicated transactions that can actually
result in an identical merkle root.
Instead of storing CCoins entries directly in CCoinsMap, store a CCoinsCacheEntry
which additionally keeps track of whether a particular entry is:
* dirty: potentially different from its parent view.
* fresh: the parent view is known to not have a non-pruned version.
This allows us to skip non-dirty cache entries when pushing batches of changes up,
and to remove CCoins entries about transactions that are fully spent before the
parent cache learns about them.
All direct modifications are now done through ModifyCoins, and BatchWrite is
used for pushing batches of queued modifications up, so we don't need the
low-level SetCoins and SetBestBlock anymore in the top-level CCoinsView class.
Replace the mutable non-copying GetCoins method with a ModifyCoins, which
returns an encapsulated iterator, so we can keep track of concurrent
modifications (as iterators can be invalidated by those) and run cleanup
code after a modification is finished.
This also removes the overloading of the 'GetCoins' name.
There is no reason to store thousands of orphan transactions;
normally an orphan's parents will either be broadcast or
mined reasonably quickly.
This pull drops the maximum number of orphans from 10,000 down
to 100, and adds a command-line option (-maxorphantx) that is
just like -maxorphanblocks to override the default.
Prevent denial-of-service attacks by banning
peers that send us invalid orphan transactions
and only storing orphan transactions given to
us by a peer while the peer is connected.
2c2cc5d Remove some unnecessary c_strs() in logging and the GUI (Philip Kaufmann)
f7d0a86 netbase: Use .data() instead of .c_str() on binary string (Wladimir J. van der Laan)
The efficient version of CCoinsViewCache::GetCoins only works for known-to-exist
cache entries, requiring a separate HaveCoins call beforehand. This is
inefficient as both perform a hashtable lookup.
Replace the non-mutable GetCoins with AccessCoins, which returns a potentially-NULL
pointer. This also decreases the overloading of GetCoins.
Also replace some copying (inefficient) GetCoins calls with equivalent AccessCoins,
decreasing the copying.
Bypassing the main coins cache allows more thorough checking with the same
memory budget.
This has no effect on performance because everything ends up in the child
cache created by VerifyDB itself.
It has bugged me ever since #4675, which effectively reduced the
number of checked blocks to reduce peak memory usage.
- Pass the coinsview to use as argument to VerifyDB
- This also avoids that the first `pcoinsTip->Flush()` after VerifyDB
writes a large slew of unchanged coin records back to the database.
