In this pull request, the state iterator is implemented. It's mostly a copy-paste
from the original state snapshot package, but still has some important changes
to highlight here:
(a) The iterator for the disk layer consists of a diff iterator and a disk iterator.
Originally, the disk layer in the state snapshot was a wrapper around the disk,
and its corresponding iterator was also a wrapper around the disk iterator.
However, due to structural differences, the disk layer iterator is divided into
two parts:
- The disk iterator, which traverses the content stored on disk.
- The diff iterator, which traverses the aggregated state buffer.
Checkout `BinaryIterator` and `FastIterator` for more details.
(b) The staleness management is improved in the diffAccountIterator and
diffStorageIterator
Originally, in the `diffAccountIterator`, the layer’s staleness had to be checked
within the Next function to ensure the iterator remained usable. Additionally,
a read lock on the associated diff layer was required to first retrieve the account
blob. This read lock protection is essential to prevent concurrent map read/write.
Afterward, a staleness check was performed to ensure the retrieved data was
not outdated.
The entire logic can be simplified as follows: a loadAccount callback is provided
to retrieve account data. If the corresponding state is immutable (e.g., diff layers
in the path database), the staleness check can be skipped, and a single account
data retrieval is sufficient. However, if the corresponding state is mutable (e.g.,
the disk layer in the path database), the callback can operate as follows:
```go
func(hash common.Hash) ([]byte, error) {
dl.lock.RLock()
defer dl.lock.RUnlock()
if dl.stale {
return nil, errSnapshotStale
}
return dl.buffer.states.mustAccount(hash)
}
```
The callback solution can eliminate the complexity for managing
concurrency with the read lock for atomic operation.
This pull request removes the destruct flag from the state snapshot to
simplify the code.
Previously, this flag indicated that an account was removed during a
state transition, making all associated storage slots inaccessible.
Because storage deletion can involve a large number of slots, the actual
deletion is deferred until the end of the process, where it is handled
in batches.
With the deprecation of self-destruct in the Cancun fork, storage
deletions are no longer expected. Historically, the largest storage
deletion event in Ethereum was around 15 megabytes—manageable in memory.
In this pull request, the single destruct flag is replaced by a set of
deletion markers for individual storage slots. Each deleted storage slot
will now appear in the Storage set with a nil value.
This change will simplify a lot logics, such as storage accessing,
storage flushing, storage iteration and so on.
* core/state/snapshot: implement storage iterator
* core/state/snapshot, tests: implement helper function
* core/state/snapshot: fix storage issue
If an account is deleted in the tx_1 but recreated in the tx_2,
the it can happen that in this diff layer, both destructedSet
and storageData records this account. In this case, the storage
iterator should be able to iterate the slots belong to new account
but disable further iteration in deeper layers(belong to old account)
* core/state/snapshot: address peter and martin's comment
* core/state: address comments
* core/state/snapshot: fix test
rjl493456442
Ikko Ashimine
Melvin Junhee Woo
Martin Michlmayr
Martin Holst Swende
Boqin Qin
Péter Szilágyi