I was baffled previously, because any time that `free` was called on a
type from an extension, it would hang even when I knew it wasn't in use
any longer, and hadn't been double free'd.
After #737 was merged, I tried it again and noticed that it would no
longer hang... but only for extensions that were staticly linked.
Then I realized that we are using a global allocator, that likely wasn't
getting used in the shared library that is built separately that won't
inherit from our global allocator in core, causing some symbol mismatch
and the subsequent hanging on calls to `free`.
This PR adds the global allocator to extensions behind a feature flag in
the macro that will prevent it from being used in `wasm` and staticly
linked environments where it would conflict with limbos normal global
allocator. This allows us to properly free the memory from returning
extension functions over FFI.
This PR also changes the Extension type to a union field so we can store
int + float values inline without boxing them.
any additional tips or thoughts anyone else has on improving this would
be appreciated 👍Closes#803
This patch adds some libSQL vector extension functions such as
`vector()` and `vector_distance_cos()`, which can be used for exact
nearest neighbor search as follows:
```
limbo> SELECT embedding, vector_distance_cos(embedding, '[9, 9, 9]')
...> FROM movies ORDER BY vector_distance_cos(embedding, '[9, 9, 9]');
[4, 5, 6]|0.013072490692138672
[1, 2, 3]|0.07417994737625122
```
