Tinkv example: is this a bug?

zeroexcuses · February 11, 2022, 2:29pm

iFaceless/tinkv/blob/master/examples/basic.rs#L19-L20


      
          store.set(k.as_bytes(), v.as_bytes())?;
          store.set(k.as_bytes(), v.as_bytes())?;

Am I missing something, or does this line look like a useless duplicate ?

jer · February 11, 2022, 3:34pm

The rest of the files explicitly checks the timing of TOTAL_KEYS * 2 writes.
So no, it's not useless.
Probably with the idea of timing the write of a non-existing key and then an existing key.

zeroexcuses · February 11, 2022, 4:41pm

I think you are spot on with it writing twice on purpose.
For bitcask, I think there is no difference between writing to non-existing key vs writing of existing key (both writes go to the segment-log). The only difference ends up during the compact phase:

github.com

iFaceless/tinkv/blob/master/examples/basic.rs#L55


      
          
          
    let value = store.get("hello".as_bytes())?;
              assert_eq!(value, Some("tinkv 2".as_bytes().to_vec()));
          
          
    store.remove("hello".as_bytes())?;
              println!("after remove: {:?}", store.stats());
          
          
    let value_not_found = store.get("hello".as_bytes())?;
              assert_eq!(value_not_found, None);
          
          
    store.compact()?;
              println!("after compaction: {:?}", store.stats());
          
          
    let v = store.get("key_1".as_bytes())?.unwrap();
              println!("key_1 => {:?}", String::from_utf8_lossy(&v));
          
          
    Ok(())
          }

With just one write, there would be no garbage to collect, but writing it twice makes the first one 'garbage' to be collected (not copied).

system · May 12, 2022, 4:42pm

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Tinkv example: is this a bug?

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