maokaihe/mini_lsm
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

finish week 1 day 6

Browse Source 
Signed-off-by: Alex Chi Z <iskyzh@gmail.com>
This commit is contained in:
Alex Chi Z
2024-01-21 17:40:47 +08:00
parent a2d8b3c865
commit fa35a7dc9e
16 changed files with 376 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
mini-lsm-book/src/week1-05-read-path.md
View File

@@ -47,18 +47,18 @@ type LsmIteratorInner =
So that our internal iterator of the LSM storage engine will be an iterator combining both data from the memtables and the SSTs.
Note that our SST iterator does not support passing a end bound to it. Therefore, we will need to handle the `end_bound` manually in `LsmIterator`. You will need to modify your `LsmIterator` logic to stop when the key from the inner iterator reaches the end boundary.
Note that our SST iterator does not support passing an end bound to it. Therefore, you will need to handle the `end_bound` manually in `LsmIterator`. You will need to modify your `LsmIterator` logic to stop when the key from the inner iterator reaches the end boundary.
Our test cases will generate some memtables and SSTs in `l0_sstables`, and you will need to scan all of these data out correctly in this task. You do not need to flush SSTs until next chapter. Therefore, you can go ahead and modify your `LsmStorageInner::scan` interface to create a merge iterator over all memtables and SSTs, so as to finish the read path of your storage engine.
Because `SsTableIterator::create` involves I/O operations and might be slow, we do not want to do this in the `state` critical region. Therefore, you should firstly take read the `state` and clone the `Arc` of the LSM state snapshot. Then, you should drop the lock. After that, you can go through all L0 SSTs and create iterators for each of them, then create a merge iterator to retrieve the data.
Because `SsTableIterator::create` involves I/O operations and might be slow, we do not want to do this in the `state` critical section. Therefore, you should firstly take read the `state` and clone the `Arc` of the LSM state snapshot. Then, you should drop the lock. After that, you can go through all L0 SSTs and create iterators for each of them, then create a merge iterator to retrieve the data.
```rust,no_run
fn scan(&self) {
let snapshot = {
let guard = self.state.read();
Arc::clone(&guard)
}
};
// create iterators and seek them
}
```
@@ -73,7 +73,7 @@ In this task, you will need to modify:
src/lsm_storage.rs
```
For get requests, it will be processed as lookups in the memtables, and then scans on the SSTs. You can create a merge iterator over all SSTs after probing all memtables. You can seek to the key that the user wants to lookup. There are two possibilities of the seek: the key is the same as what the user probes, and the key is not the same / does not exist. You should only return the value to the user when the key exists and is the same as probed. You should also reduce the critical region of the state lock as in the previous section. Also remember to handle deleted keys.
For get requests, it will be processed as lookups in the memtables, and then scans on the SSTs. You can create a merge iterator over all SSTs after probing all memtables. You can seek to the key that the user wants to lookup. There are two possibilities of the seek: the key is the same as what the user probes, and the key is not the same / does not exist. You should only return the value to the user when the key exists and is the same as probed. You should also reduce the critical section of the state lock as in the previous section. Also remember to handle deleted keys.
## Test Your Understanding