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https://issues.apache.org/jira/browse/ARROW-1712?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16327454#comment-16327454
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ASF GitHub Bot commented on ARROW-1712:
---------------------------------------
wesm commented on issue #1481: ARROW-1712: [C++] Add method to BinaryBuilder to
reserve space for value data
URL: https://github.com/apache/arrow/pull/1481#issuecomment-358045671
@xuepanchen thank you for your contribution. We need to add a new method to
`BinaryBuilder` for this use case.
To give an example, suppose that we anticipate building an array with 1000
elements, each of which has an expected size of around 100 bytes. You would
want to write something like:
```
RETURN_NOT_OK(builder.Reserve(1000));
RETURN_NOT_OK(builder.ReserveData(100 * 1000));
```
(@xhochy do you have an opinion on what to call this?)
Please also add a method to return the capacity of the internal
`value_data_builder_` and add unit tests to `array-test.cc`. Thanks!
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> [C++] Add method to BinaryBuilder to reserve space for value data
> -----------------------------------------------------------------
>
> Key: ARROW-1712
> URL: https://issues.apache.org/jira/browse/ARROW-1712
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++
> Reporter: Wes McKinney
> Assignee: Panchen Xue
> Priority: Major
> Labels: pull-request-available
> Fix For: 0.9.0
>
>
> The {{Resize}} and {{Reserve}} methods only reserve space for the value
> offsets. When building binary/string arrays with a known size (or some
> reasonable estimate), it would be more efficient to reserve once at the
> beginning to prevent internal reallocations
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