jjbskir commented on a change in pull request #9142:
URL: https://github.com/apache/arrow/pull/9142#discussion_r555825490
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File path: docs/source/java/vector.rst
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@@ -217,6 +217,55 @@ to be declared is that writer/reader is not as efficient
as direct access
}
}
+Building ListVector
+==================
+
+A :class:`ListVector` is a vector that holds a list of values for each index.
Working with one you need to handle the same steps as mentioned above (create >
allocate > mutate > set value count > access > clear), but the details of how
you accomplish this are slightly different since you need to both create the
vector and set the list of values for each index.
+
+For example, the code below shows how to build a :class:`ListVector` of int's
using the writer :class:`UnionListWriter`. We build a vector from 0 to 9 and
each index contains a list with increasing values [[0, 0, 0, 0, 0], [0, 1, 2,
3, 4], [0, 2, 4, 6, 8], …, [0, 9, 18, 27, 36]].
+
Review comment:
Hey yea that is a possibility. We can always write in the docs that the
values can be added in arbitrary order. Or instead of using a for loop to add
the values we can have some predefined arrays we want to add in that have
arbitrary order like: [[1, 2, 3], [3, 2, 1], [10, 30, 20]]. Also looking at the
[tests for
ListVector](https://github.com/apache/arrow/blob/25c736d48dc289f457e74d15d05db65f6d539447/java/vector/src/test/java/org/apache/arrow/vector/TestListVector.java)
it looks like they all use ascending order.
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