feat: Use LazyLock for static schema caching in AvroSchema impl

[flxo]

Changed the generated get_schema() implementation to cache parsed schemas using std::sync::OnceLock instead of parsing on every call.

Performance improvement (measured with criterion on a MacBook Pro M4):

• Without cache: ~11.77 µs per call
• With cache: ~701 ns per call
• Speedup: ~16.8x faster

The cache uses lazy initialization with lock-free reads after the first access, providing significant performance gains for applications that frequently call get_schema() with minimal memory overhead.

Changes:

• src/templates.rs: Updated template to use std::sync::OnceLock
• tests/schemas/*: Updated expected test outputs
• Added benchmark to measure performance impact

The PR includes a criterion benchmark. I'm happy to remove that before merging but kept for now as reference.

[Kriskras99]

I did not expect that this would have so much of an impact because of the .clone(), good that you tried it out!

I would suggest using a LazyLock instead of a OnceLock, as a OnceLock is designed for use with different init functions while LazyLock is designed for use with a "static" init function.

Also, you should use ::std instead of std in case a user overrides the std name in their file.

[flxo]

I would suggest using a LazyLock instead of a OnceLock, as a OnceLock is designed for use with different init functions while LazyLock is designed for use with a "static" init function.

thanks for the hint. Valid point - I updated the PR.

Also, you should use ::std instead of std in case a user overrides the std name in their file.

Updated.

[lerouxrgd]

Thanks for this good PR too ! After fixing formatting it should be good to merge, let's keep the criterion benchmark :)

[lerouxrgd]

Thanks !

[flxo]

Thanks for merging and the crates.io release. I just noticed that a additional fn that returns &Schema could be beneficial. This would be in addition to the AvroSchema impl. For using apache-avro there's not an owned version of Schema needed and a ref is enough. This would avoid the clone.