refactor(storage): store direct value entry index in imm iter #15417
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MrCroxx
approved these changes
Mar 6, 2024
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| /// Return an exclusive offset of the values of key of index `i` | ||
| fn value_end_offset<'a>( | ||
| i: usize, | ||
| entries: &'a [SharedBufferKeyEntry], | ||
| values: &'a [VersionedSharedBufferValue], | ||
| ) -> usize { | ||
| entries | ||
| .get(i + 1) | ||
| .map(|entry| entry.value_offset) | ||
| .unwrap_or(values.len()) | ||
| } | ||
|
|
||
| fn values<'a>( | ||
| i: usize, | ||
| entries: &'a [SharedBufferKeyEntry], | ||
| values: &'a [VersionedSharedBufferValue], | ||
| ) -> &'a [VersionedSharedBufferValue] { | ||
| &values[entries[i].value_offset | ||
| ..entries | ||
| .get(i + 1) | ||
| .map(|entry| entry.value_offset) | ||
| .unwrap_or(values.len())] | ||
| &values[entries[i].value_offset..value_end_offset(i, entries, values)] |
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Should we make them member functions of SharedBufferKeyEntry to simplify the definition? It seems they are called nowhere else besides SharedBufferKeyEntry.
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What's changed and what's your intention?
Previously in #15300, we store all versions of values in a single vec. However, the
current_value_idxof imm iter still means the index of current value in the sub-slice of values of current key. In this PR, we change to letcurrent_value_idxbe the direct index to the single vec of values of all keys, so that we can get the current value directly without computing the index.A bug of backward iter is fixed by the way in this PR. In our previous implementation, for a single key, the backward iter iterates its value from older epoch to newer. However, backward only means the key direction. For difference versions of a single key, we should iterate from newer epoch to older one as what forward iter does.
This PR is separated from #15300 because it needs careful review.
Checklist
./risedev check(or alias,./risedev c)Documentation
Release note
If this PR includes changes that directly affect users or other significant modifications relevant to the community, kindly draft a release note to provide a concise summary of these changes. Please prioritize highlighting the impact these changes will have on users.