Return Cow<[u8]> instead of &[u8] in storage abstraction layer #652
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TheQuantumPhysicist
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muursh,
erubboli,
iljakuklic and
stanislav-tkach
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TheQuantumPhysicist
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stanislav-tkach
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Jan 25, 2023
iljakuklic
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Jan 26, 2023
| @@ -34,7 +36,7 @@ pub trait PrefixIter<'i> { | |||
| /// Read-only database operations | |||
| pub trait ReadOps: for<'i> PrefixIter<'i> { | |||
| /// Get value associated with given key. | |||
| fn get(&self, idx: DbIndex, key: &[u8]) -> crate::Result<Option<&[u8]>>; | |||
| fn get(&self, idx: DbIndex, key: &[u8]) -> crate::Result<Option<Cow<[u8]>>>; | |||
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Maybe the Option<Cow<[u8]>> part deserves an alias. Cannot think of a suitable name though. Maybe DbData or DbValue? Not sure. Would also resolve the Clippy warnings about type complexity.
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Generally speaking, it's not possible to get a slice of bytes from all storage backends with arbitrary lifetime. This is because this assumes that all the data is readily available for reading directly from the database. This is more of a wish.
In this PR we return
Cow<[u8]>instead of&[u8]from the storage interface's get() function.Using an owned value would be the last resort if a storage layer does not provide solutions for getting values by reference.