Can not distinguish between "does not exist" and "has no value" #726

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1. Elbehery commented on Apr 17, 2024

   

   Elbehery

   on Apr 17, 2024

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   @ceving Get returns nil if the key does not exist, or the value is a nested bucket

   this could be a feature cc @ahrtr @fuweid @tjungblu @ivanvc
2. ahrtr commented on Apr 17, 2024

   

   ahrtr

   on Apr 17, 2024

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   For the case of "does not exist", bucket.Get returns nil.

   For the case "has no value", bucket.Get returns []byte{}, which is obviously not nil.

   The only known minor problem is that even you write a nil value for a key, when you read it back in a separate transaction, it still returns []byte{}.

   👍React with 👍1Reacted by Thomas Jungblut
3. ahrtr commented on Apr 17, 2024

   

   ahrtr

   on Apr 17, 2024

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   For example,

   func TestBucket_Get_NonExistent(t *testing.T) {
   	db := btesting.MustCreateDB(t)
   
   	if err := db.Update(func(tx *bolt.Tx) error {
   		b, err := tx.CreateBucket([]byte("widgets"))
   		if err != nil {
   			t.Fatal(err)
   		}
   		return b.Put([]byte("foo"), nil)
   	}); err != nil {
   		t.Fatal(err)
   	}
   
   	db.View(func(tx *bolt.Tx) error {
   		b := tx.Bucket([]byte("widgets"))
   		if v := b.Get([]byte("foo")); v != nil {
   			t.Fatal("expected nil value")  // The test case will fail here.
   		}
   		return nil
   	})
   }
   
   
4. ahrtr commented on Apr 17, 2024

   

   ahrtr

   on Apr 17, 2024

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   In short, no matter what value you write into bbolt, when you read it back, you will always get []byte{} as long as len(value) == 0 is true.

   The only exception is that when you write a nil value, and you will still get a nil value when you read it back in the same transaction.

   Will raise a PR to add a known issue.
5. ahrtr commented on Apr 18, 2024

   

   ahrtr

   on Apr 18, 2024

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   Completed in #730
6. ahrtr

   closed this as completedon Apr 18, 2024