Ben Kietzman created ARROW-8022:
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Summary: [C++] Provide or Vendor a small_vector implementation
Key: ARROW-8022
URL: https://issues.apache.org/jira/browse/ARROW-8022
Project: Apache Arrow
Issue Type: Improvement
Components: C++
Affects Versions: 0.16.0
Reporter: Ben Kietzman
Assignee: Ben Kietzman
Fix For: 1.0.0
{{small_vector<>}} is a C++ utility class which does not use heap allocation
for small numbers of elements.
[Folly|https://github.com/facebook/folly/blob/master/folly/docs/small_vector.md],
[Boost|https://github.com/boostorg/container/blob/develop/include/boost/container/small_vector.hpp],
[Abseil|https://github.com/abseil/abseil-cpp/blob/master/absl/container/inlined_vector.h],
and [LLVM|https://llvm.org/doxygen/classllvm_1_1SmallVector.html] each provide
one.
In many cases a vector usually has few elements but might have many. If we use
std::vector we have to bother the allocator unless the vector is actually
empty. My specific use case for this is field lookup by name: I expect that
most schemas will have unique field names, but strictly speaking we support
duplicate field names. It would be ideal not incur a performance penalty for
99.9% of field lookups which yield 0 or 1 fields just to accommodate the case
where there may be multiple.
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