core/state/snapshot: clarify comment about snapshot repair (#23305)

Co-authored-by: Tyler Chambers <me@tylerchambers.net>
Co-authored-by: Felix Lange <fjl@twurst.com>
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Tyler Chambers 2021-08-10 05:16:53 -04:00 committed by GitHub
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@ -169,11 +169,17 @@ type Tree struct {
// store (with a number of memory layers from a journal), ensuring that the head
// of the snapshot matches the expected one.
//
// If the snapshot is missing or the disk layer is broken, the entire is deleted
// and will be reconstructed from scratch based on the tries in the key-value
// store, on a background thread. If the memory layers from the journal is not
// continuous with disk layer or the journal is missing, all diffs will be discarded
// iff it's in "recovery" mode, otherwise rebuild is mandatory.
// If the snapshot is missing or the disk layer is broken, the snapshot will be
// reconstructed using both the existing data and the state trie.
// The repair happens on a background thread.
//
// If the memory layers in the journal do not match the disk layer (e.g. there is
// a gap) or the journal is missing, there are two repair cases:
//
// - if the 'recovery' parameter is true, all memory diff-layers will be discarded.
// This case happens when the snapshot is 'ahead' of the state trie.
// - otherwise, the entire snapshot is considered invalid and will be recreated on
// a background thread.
func New(diskdb ethdb.KeyValueStore, triedb *trie.Database, cache int, root common.Hash, async bool, rebuild bool, recovery bool) (*Tree, error) {
// Create a new, empty snapshot tree
snap := &Tree{