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https://issues.apache.org/jira/browse/ARROW-17824?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jin Shang reassigned ARROW-17824:
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Assignee: Jin Shang
> [C++][Gandiva] Implement preallocation for variable length output buffer
> -------------------------------------------------------------------------
>
> Key: ARROW-17824
> URL: https://issues.apache.org/jira/browse/ARROW-17824
> Project: Apache Arrow
> Issue Type: Improvement
> Components: C++ - Gandiva
> Affects Versions: 9.0.0
> Reporter: Jin Shang
> Assignee: Jin Shang
> Priority: Major
>
> When the output type of an expression is of variable length, e.g. string,
> Gandiva would realloc the output buffer to make space for new outputs for
> each row. When num of rows is high some memory allocators perform poorly.
> We can use the std::vector like approach to amortize the allcation cost.
> First allocate some initial space depending on the input size. Each time we
> run out of space, double the buffer size. In the end shrink it to fit the
> actual size.
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