* Make `Page` always fully init
Per discussion on the snapshotting proposal,
this PR changes the type of `Page.row_data` to `[u8; _]`,
where previously it was `[MaybeUninit<u8>; _]`.
This turns out to be shockingly easy,
as our serialization codepaths never write padding bytes into a page.
The only place pages ever became `poison` was the initial allocation;
changing this to `alloc_zeroed` causes the `row_data` to always be valid at `[u8; _]`.
The majority of this diff is replacing `MaybeUninit`-specific operators
with their initialized equivalents,
and updating comments and documentation to reflect the new requirements.
This change also revealed a bug in the benchmarks
introduced when we swapped the order of sum tags and payloads
( https://github.com/clockworklabs/SpacetimeDB/pull/1063 ),
where benchmarks used a hardcoded offset for the tag which had not been updated.
* Update blake3
Blake3 only supports running under Miri as of 1.15.1, the latest version.
Prior versions hard-depended on SIMD intrinsics which Miri doesn't support.
* Address Mazdak's review.
Still pending his agreeing with me that `poison` is a better name than `uninit`.
* "Poison" -> "uninit"
Against my best wishes, for consistency with the broader Rust community's poor choices.
* Remove unnecessary `unsafe` blocks
* More unnecessary `unsafe`; remove forgotten SAFETY comments
2. Make `RowRef::row_hash` use the above.
3. Make `Table::insert` return a `RowRef`.
4. Use less unsafe because of 1-3.
5. Use `second-stack` to reuse temporary allocations in hashing and serialization.
- Arcing `TableSchema`, and this has benefits elsewhere too.
- Arc<[_]>ing the visitor program instructions.
The data behind the Arcs very rarely change,
which is the perfect case for an Arc.
- Move it and friends from sats to vm.
- MemTable now stores a Vec<PV>.
- Other related improvements.
Co-authored-by: Phoebe Goldman <phoebe@goldman-tribe.org>
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