[Java][ListView] Implementation of the ListView

[davisusanibar]

Describe the enhancement requested

C++, Go, and Python all support ListView. The goal of this enhancement is to expand the Arrow Java format input for ListView.

This could be an initial proposal for ListViewVector based on current LisVector implementation:

Using ListViewVector:

...
// values = [12, -7, 25, 0, -127, 127, 50]
// offsets = [0, 7, 3, 0]
// sizes = [3, 0, 4, 0]
// data to get thru listview: [[12,-7,25], null, [0,-127,127,50], []]
...
listViewVector.allocateNew();
inVector.allocateNew();

inVector.setSafe(0, 12);
inVector.setSafe(1, -7);
inVector.setSafe(2, 25);
inVector.setSafe(3, 0);
inVector.setSafe(4, -127);
inVector.setSafe(5, 127);
inVector.setSafe(6, 50);

listViewVector.startNewValue(0, 0); // (0=index, 0=offset)
listViewVector.endValue(0, 3); //(0=index, 3=number of items)

listViewVector.setNull(1);

listViewVector.startNewValue(2, 3);
listViewVector.endValue(2, 4);

listViewVector.startNewValue(3, 0);
listViewVector.endValue(3, 0);

listViewVector.setValueCount(4);

...

assertEquals(inVector.toString(), "[12, -7, 25, 0, -127, 127, 50]");
assertEquals(listViewVector.toString(), "[[12,-7,25], null, [0,-127,127,50], []]");

Using Writers:

// values = [12, -7, 25, 0, -127, 127, 50]
// offsets = [0, 7, 3, 0]
// sizes = [3, 0, 4, 0]
// data to get thru listview: [[12,-7,25], null, [0,-127,127,50], []]
...
UnionListViewWriter writer = inVector.getWriter();
writer.allocate();

writer.setPosition(0);
writer.startList(0); // (0=offset)
writer.bigInt().writeBigInt(12);
writer.bigInt().writeBigInt(-7);
writer.bigInt().writeBigInt(25);
writer.endList(3); // (3=number of items)


writer.setPosition(2);
writer.startList(3);
writer.bigInt().writeBigInt(0);
writer.bigInt().writeBigInt(-127);
writer.bigInt().writeBigInt(127);
writer.bigInt().writeBigInt(50);
writer.endList(4);

writer.setPosition(3);
writer.startList(0);
writer.endList(0);

writer.setValueCount(4);

...

assertEquals(inVector.getDataVector().toString(), "[12, -7, 25, 0, -127, 127, 50]");
assertEquals(inVector.toString(), "[[12,-7,25], null, [0,-127,127,50], []]");

Component(s)

Java

[vibhatha]

Closing this issue in favor of apache/arrow-java#102