This PR is the first step in the trienode history series.
It introduces the `nodeWithOrigin` struct in the path database, which tracks
the original values of dirty nodes to support trienode history construction.
Note, the original value is always empty in this PR, so it won't break the
existing journal for encoding and decoding. The compatibility of journal
should be handled in the following PR.
This pull request introduces a mechanism to improve state lookup
efficiency in pathdb by maintaining a lookup structure that eliminates
unnecessary iteration over diff layers.
The core idea is to track a mutation history for each dirty state entry
residing in the diff layers. This history records the state roots of all layers
in which the entry was modified, sorted from oldest to newest.
During state lookup, this mutation history is queried to find the most
recent layer whose state root either matches the target root or is a
descendant of it. This allows us to quickly identify the layer containing
the relevant data, avoiding the need to iterate through all diff layers from
top to bottom.
Besides, the overhead for state lookup is constant, no matter how many
diff layers are retained in the pathdb, which unlocks the potential to hold
more diff layers.
Of course, maintaining this lookup structure introduces some overhead.
For each state transition, we need to:
(a) update the mutation records for the modified state entries, and
(b) remove stale mutation records associated with outdated layers.
On our benchmark machine, it will introduce around 1ms overhead which is
acceptable.
This pull request ports some changes from the main state snapshot
integration one, specifically introducing the flat state tracking in
pathdb.
Note, the tracked flat state changes are only held in memory and won't
be persisted in the disk. Meanwhile, the correspoding state retrieval in
persistent state is also not supported yet. The states management in
disk is more complicated and will be implemented in a separate pull
request.
Part 1: https://github.com/ethereum/go-ethereum/pull/30752
