Structured ByteView Access (underlying StringView/BinaryView representation)

[tustvold]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

There have been a couple of proposals to improve the ergonomics of interacting with byte views

• Add ByteView::try_new #5735
• Encapsulate View logic for GenericByteViewArray #5619

The current design of the byte views assumes calling sites know the structure of the u128, #5735 tweaks this a little bit but the onus is still on the user to understand the layout of the views.

Describe the solution you'd like

TBD

Describe alternatives you've considered

Additional context

[alamb]

Related discussion #5654 (comment)

I think this basically means the intention is that we (well @tustvold ) plans to replace u128 in ByteViewArray with an actual structured type of some sort

[alamb]

#5796 is up for feedback

[tustvold]

#5786 provides a high-level interface for constructing views, which mirrors the high-level interface exposed by ByteViewArray for accessing them.

This means users shouldn't ever need to deal with the underlying representation. I think we therefore could just close this ticket.

For completeness I have spent some time trying to come up with a better abstraction than u128 and have struggled.

There are a couple of major challenges:

• String prefixes are not necessarily valid unicode
• Certain operations exploit the layout in ways LLVM seems unable to come up with, e.g.
  • Compare the length and prefix in a single u64 comparison
  • Elide length checking once checked length and prefix together

That isn't to say a better abstraction isn't possible, but it is fiddly and the major forcing function of construction is resolved by #5786. I think a smaller incremental PR like #5735 may therefore be all we need for the time being. We can always revisit in 3 months time when we look to do the next breaking release.

[alamb]

I like the plan of going with what we have (which is now a bit nicer) and waiting another three months for any breaking change

We can always add things on top of the u128s (e.g. similar to #5619) if we need something more ergonomic

[alamb]

@tustvold do you have any more plans for this issue in the next week? I think @XiangpengHao is going to be helping work on ByteView features over the next few days but also that that shouldn't really affect this ticket

[tustvold]

I do not intend to do anything further with this ticket at this time, no