core/rawdb, triedb/pathdb: introduce trienode history#32596
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| value := h.nodes[owner][path] | ||
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| // key section | ||
| n := binary.PutUvarint(buf[0:], uint64(prefixLen)) // key length shared (varint) |
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I don't really get why this is needed
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Inside of the restart, these rules are applied:
- the first entry is always encoded with full key
- for all the subsequent entries, the key is encoded in a "compressed" format.
In which, only the difference between the key and preceding one is stored. Given
that we store the trie nodes here and the key is essentially the node path. By storing
the diff can effectively compress the entry key.
Therefore, a few additional metadata are tracked in the key section:
- shared key length
- unshared key length
- value length
These information can support us to recover the key from the byte stream.
| ) | ||
| for i, path := range h.nodeList[owner] { | ||
| key := []byte(path) | ||
| if i%trienodeDataBlockRestartLen == 0 { |
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Same with this, I don't understand why we need the block restarts and why the sharedPrefix will be 0 if we chunk
| if len(keySection) < int(8*nRestarts)+4 { | ||
| return nil, fmt.Errorf("key section too short, restarts: %d, size: %d", nRestarts, len(keySection)) | ||
| } | ||
| for i := 0; i < int(nRestarts); i++ { | ||
| o := len(keySection) - 4 - (int(nRestarts)-i)*8 | ||
| keyOffset := binary.BigEndian.Uint32(keySection[o : o+4]) | ||
| if i != 0 && keyOffset <= keyOffsets[i-1] { | ||
| return nil, fmt.Errorf("key offset is out of order, prev: %v, cur: %v", keyOffsets[i-1], keyOffset) |
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There are so many magic numbers here... its hard to comprehend
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The nodes from different tries are aggregated and concatenated within the key and value sections.
The offsets of the keys and values belonging to each trie are recorded in the header section.
For each trie, a list of internal chunks, called as restarts, is maintained.
At the end of the key section corresponding to a given trie, the offsets of these restarts are recorded.
These codes are for resolving the offsets of these restarts.
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There are two main reasons for maintaining these restarts:
(1) compress the entry key
Given that the key length of the entry (trie node) is not negligible. By maintaining the difference with the preceding one (usually parent node) can compress the key length effectively. Usually 1 byte diff is sufficient.
(2) enhance the lookup efficiency
The first entry in the restart is always stored with full key (no shared part with the preceding one). Therefore the binary search can be performed at the boundary of restarts.
MariusVanDerWijden
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Generally LGTM, small nits and a few questions
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It's a pull request based on the ethereum#32523 , implementing the structure of trienode history.
It's a pull request based on the ethereum#32523 , implementing the structure of trienode history.
It's a pull request based on the ethereum#32523 , implementing the structure of trienode history.
It's a pull request based on the ethereum#32523 , implementing the structure of trienode history.
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It's a pull request based on the #32523 , implementing the structure of trienode history.