Liya Fan created ARROW-7213:
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Summary: [Java] Represent a data element of a vector as a tree of
ArrowBufPointer
Key: ARROW-7213
URL: https://issues.apache.org/jira/browse/ARROW-7213
Project: Apache Arrow
Issue Type: New Feature
Components: Java
Reporter: Liya Fan
Assignee: Liya Fan
For a fixed/variable width vector, each of its data element can be represented
as an ArrowBufPointer object, which represents a contiguous memory segment.
This makes many tasks easier and more efficient (without memory copy):
calculating hash code, comparing values, etc.
This cannot be achieved for complex vectors, because their values often reside
in more than one contiguous memory regions. However, it can be seen that the
contiguous memory regions for each data element forms a tree-like structure,
whose leaf nodes are the contiguous memory regions. For example, a data element
for a struct vector forms a tree, whose root corresponds to the struct vector,
while the child vectors corresponds to the child nodes of the tree root.
In this issue, we provide a data structure that represents each data element of
a vector as a tree, whose leaf nodes are ArrowBufPointers, representing
contiguous memory regions for the data element.
With this data structure, many tasks also becomes easier and more efficient:
calculating hash code, comparing vector elements (ordering & equality). In
addition, we can do something that could not have been done in the past, like
placing data elements into a hash table/hash set, etc.
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