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add key abstraction and prepare for MVCC (#28)

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* add key abstraction and prepare for MVCC

Signed-off-by: Alex Chi <iskyzh@gmail.com>

* a little bit type exercise

Signed-off-by: Alex Chi <iskyzh@gmail.com>

* refactor tests

Signed-off-by: Alex Chi <iskyzh@gmail.com>

* fix clippy warnings

Signed-off-by: Alex Chi <iskyzh@gmail.com>

* refactor starter code

Signed-off-by: Alex Chi <iskyzh@gmail.com>

* final touch docs

Signed-off-by: Alex Chi <iskyzh@gmail.com>

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Signed-off-by: Alex Chi <iskyzh@gmail.com>
This commit is contained in:
Alex Chi Z
2024-01-25 10:59:08 +08:00
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parent 2fefe3e505
commit a3a92359e1
42 changed files with 824 additions and 281 deletions
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mini-lsm-book/src/week1-02-merge-iterator.md
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@@ -94,7 +94,9 @@ let Some(mut inner_iter) = self.iters.peek_mut() {
If `next` returns an error (i.e., due to disk failure, network failure, checksum error, etc.), it is no longer valid. However, when we go out of the if condition and return the error to the caller, `PeekMut`'s drop will try move the element within the heap, which causes an access to an invalid iterator. Therefore, you will need to do all error handling by yourself instead of using `?` within the scope of `PeekMut`.
We want to avoid dynamic dispatch as much as possible, and therefore we do not use `Box<dyn StorageIterator>` in the system. Instead, we prefer static dispatch using generics.
We want to avoid dynamic dispatch as much as possible, and therefore we do not use `Box<dyn StorageIterator>` in the system. Instead, we prefer static dispatch using generics. Also note that `StorageIterator` uses generic associated type (GAT), so that it can support both `KeySlice` and `&[u8]` as the key type. We will change `KeySlice` to include the timestamp in week 3 and using a separate type for it now can make the transition more smooth.
Starting this section, we will use `Key<T>` to represent LSM key types and distinguish them from values in the type system. You should use provided APIs of `Key<T>` instead of directly accessing the inner value. We will add timestamp to this key type in part 3, and using the key abstraction will make the transition more smooth. For now, `KeySlice` is equivalent to `&[u8]`, `KeyVec` is equivalent to `Vec<u8>`, and `KeyBytes` is equivalent to `Bytes`.
## Task 3: LSM Iterator + Fused Iterator