Add finish_cloned to ArrayBuilder

[askoa]

Which issue does this PR close?

Closes #3154

Are there any user-facing changes?

Yes, users will get a new function finish_cloned to get snapshot of data in ArrayBuilder without resetting the builder.

[tustvold]

I wonder if instead of MutableBuffer: Clone and adding finish_cloned to BufferBuilder, etc... we could just make use of https://docs.rs/arrow-buffer/latest/arrow_buffer/struct.Buffer.html#method.from_slice_ref?

e.g.

let buffer = Buffer::from_slice_ref(self.values_builder.as_slice());

What do you think?

[askoa]

I wonder if instead of MutableBuffer: Clone and adding finish_cloned to BufferBuilder, etc... we could just make use of https://docs.rs/arrow-buffer/latest/arrow_buffer/struct.Buffer.html#method.from_slice_ref?

e.g.

let buffer = Buffer::from_slice_ref(self.values_builder.as_slice());

What do you think?

I made the change locally and getting below error

Error for BooleanBufferBuilder:

"the size for values of type `[u8]` cannot be known at compilation time\nthe trait `Sized` is not implemented for `[u8]`"

Error for BufferBuilder:

"the size for values of type `[T]` cannot be known at compilation time\nthe trait `Sized` is not implemented for `[T]`"

[tustvold]

Aah yeah, the signature for Buffer::from_slice_ref is a little strange... Buffer::from_slice_ref(&self.values_builder.as_slice()); should work

[askoa]

Aah yeah, the signature for Buffer::from_slice_ref is a little strange... Buffer::from_slice_ref(&self.values_builder.as_slice()); should work

The suggestion works. I'll send complete PR.

Edit: I think finish_cloned function needs to be added to null_buffer_builder as null_buffer_builder.bitmap_builder might not be accessible outside the struct.

[tustvold]

Edit: I think finish_cloned function needs to be added to null_buffer_builder as null_buffer_builder.bitmap_builder might not be accessible outside the struct.

I'd suggest adding something like

    /// Returns the packed bits
    pub fn as_slice(&self) -> Option<&[u8]> {
        Some(self.bitmap_builder?.as_slice())
    }

[tustvold]

Just some minor nits

[ursabot]

Benchmark runs are scheduled for baseline = 12a67b9 and contender = 6c466af. 6c466af is a master commit associated with this PR. Results will be available as each benchmark for each run completes.
Conbench compare runs links:
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ec2-t3-xlarge-us-east-2] ec2-t3-xlarge-us-east-2
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on test-mac-arm] test-mac-arm
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-i9-9960x] ursa-i9-9960x
[Skipped ⚠️ Benchmarking of arrow-rs-commits is not supported on ursa-thinkcentre-m75q] ursa-thinkcentre-m75q
Buildkite builds:
Supported benchmarks:
ec2-t3-xlarge-us-east-2: Supported benchmark langs: Python, R. Runs only benchmarks with cloud = True
test-mac-arm: Supported benchmark langs: C++, Python, R
ursa-i9-9960x: Supported benchmark langs: Python, R, JavaScript
ursa-thinkcentre-m75q: Supported benchmark langs: C++, Java