[C++] FixedSizeListBuilder should have UnsafeAppend methods

[pitrou]

Describe the enhancement requested

The following methods are missing from FixedSizeListBuilder and would be useful for high-performance fixed-size-list array building:

• void UnsafeAppend()
• void UnsafeAppendNull()
• void UnsafeAppendNulls(int64_t length)

Ideally the PR should also grep through the source code and convert candidate call sites to the new APIs.

Component(s)

C++

[gauravrp]

Hi @pitrou
I would like to pick this up to get to know more on apache arrow, and this would be my first commit.
Would you suggest me picking this up?

[wgtmac]

@gauravrp Feel free to submit a PR for this!

[cramosme]

Hello, I am a student looking to make my first contribution. I saw that this issue was still open and didn't find a pull request that matched it. Is it okay if I work on this?

[pitrou]

@gauravrp Do you still want to work on this as you proposed above? If not, then @cramosme can take it up.

[gauravrp]

Hey @cramosme
Please feel free to pick this issue, and apologies for late replies.

[geonove]

@cramosme Are you still working on this? If not I would like to give this a try

[cramosme]

@geonove I submitted a PR, but hasn't been looked at yet. Not sure if I missed a step. If you would like to work on it, I can close it and let you give it a shot.

[geonove]

@cramosme I see, we came to a the same implementation 👍
You should link this issue in the PR, might have better chances to get it reviewed :)

[kou]

#46126 ?
Could you follow auto-generated comment #46126 (comment) to fix PR style?