[Java] Add ListVector#setInitialCapacity overload that takes an exact inner capacity

[lidavidm]

Describe the enhancement requested

ListVector (or really, its abstract base class) adds an overload of setInitialCapacity that also preallocates the inner vector based on the "density" of the list items. However sometimes you know the number of inner elements up front, so it would be clearer (and less error-prone) to just tell the vector this fact.

You could do this by manipulating the inner vector directly but given we have the other overload, this one also makes sense.

Component(s)

Java

[jduo]

take

[jduo]

Not sure if I follow this issue. There is already setInitialCapacity(int numRecords) on both BaseRepeatedValueVector and ListVector so I'm not clear on what's missing.

[lidavidm]

There's a setInitialCapacity (linked above) that also sets the child vector's capacity at the same time, but only works off an estimate of the child vector's capacity; it would make sense to also have a version that is exact

[jduo]

This seems like adding a setInitialCapacity(int, int) overload for specifying the exact number of elements in each inner list.

[lidavidm]

Yes, except I think the latter parameter would be the total number of elements across all lists

[jduo]

Hmm, that seems error prone though. That there's a setInitialCapacity(int, double) where the last parameter is the density/elements per list and another that's setInitialCapacity(int, int) where the last parameter is the total number of elements across all lists.

[lidavidm]

Fair point; we could give the latter a different name? Or we could cancel this and have @davisusanibar document how to explicitly set the list and child capacities separately.

[jduo]

I'm favoring creating a separate method setInitialTotalCapacity() or something along those lines.

[lidavidm]

Sounds good to me.