hrishisd opened a new pull request, #37844:
URL: https://github.com/apache/arrow/pull/37844
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### Rationale for this change
This change prevents avoidable `OversizedAllocationException`s when
appending a variable-length vector with many small elements to a
variable-length vector with a few large elements.
When appending variable-length vectors, `VectorAppender` iteratively doubles
the offset and validity buffers until they can accommodate the combined
elements. In the previous implementation, each iteration would also double the
data buffer's capacity. This behavior is appropriate for vectors of fixed-size
types but can result in an oversized data buffers when appending many small
elements to a variable length vector with a large data buffer.
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### What changes are included in this PR?
The new behavior only resizes the offset and validity buffers when resizing
the target vector's buffers to ensure they can hold the total number of
combined elements.
The data buffer is resized based on the total required data size of the
combined elements.
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### Are these changes tested?
Yes. I added a unit test that results in an `OversizedAllocationException`
when run against the previous version of the code.
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### Are there any user-facing changes?
No.
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