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Antoine Pitrou authored and Wes McKinney committed b1025c23be6
ARROW-6481: [C++] Avoid copying large ConvertOptions If you have N columns and a large subset of them are customized in ConvertOptions, copying ConvertOptions in each Converter or ColumnBuilder produces a quadratic explosion. With this PR, the reproducer in ARROW-6481 drops down from 8 seconds to 100 ms (on my machine). And it doesn't consume 8 GB RAM anymore. Closes #5334 from pitrou/ARROW-6481-large-convert-options and squashes the following commits: 967142e23 <Antoine Pitrou> ARROW-6481: Avoid copying large ConvertOptions Authored-by: Antoine Pitrou <antoine@python.org> Signed-off-by: Wes McKinney <wesm+git@apache.org>