Add Index::merge_from + Index::insert exploits stuff for perf.#4086
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Add Index::merge_from + Index::insert exploits stuff for perf.#4086
Index::merge_from + Index::insert exploits stuff for perf.#4086Conversation
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gefjon
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Jan 22, 2026
| /// The relation `key -> ptr` must not exist in the index. | ||
| /// Note that inserting `key -> ptr_other`, | ||
| /// where `ptr != ptr_other`, is legal. | ||
| fn insert_maybe_despecialize( |
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Why is this method not marked unsafe, when it has a Safety section in its docs and you're calling it with an unsafe block?
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| #[cfg(test)] | ||
| fn insert_for_test(&mut self, key: Self::Key, ptr: RowPointer) -> Result<(), RowPointer> { | ||
| // SAFETY: proof obligation checked inside the method for debug builds. |
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Does cfg(test) necessarily imply cfg(debug_assertions)?
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| // SAFETY: The intersection is empty, so `dst ++ src` is also a set. | ||
| dst.append(&mut src); |
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Do we need to potentially upgrade here to a Self::Large if the two sets combined meet some size threshold?
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Description of Changes
This PR:
Index::merge_from(&mut self, src: Self), which mergessrcintoself. This will be used to speed up merging of transactions.Index::insertto exploit a property for improved performance in itself and inIndex::merge_from.(key, ptr)occurs twice. This was always the case, but now it is a safety invariant and exploited for performance. This then is bubbled up toMutTxIdand friends.API and ABI breaking changes
None
Expected complexity level and risk
4 - This touches both
Index::insert,Table, andMutTxIdin terms ofunsafe.Testing
Index::insert.merge_from_is_unionis added that comprehensively exercisesIndex::{insert, merge_from, can_merge}together and for all index kinds and uniqueness.