add zlib_crc32_fixed

[BiteTheDDDDt]

What problem does this PR solve?

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

Release note

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Check List (For Author)

• Test

  • Regression test
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  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
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• Behavior changed:

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• Does this need documentation?

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Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
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[hello-stephen]

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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
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4. Which code was refactored and why was this part of the code refactored?
5. Which functions were optimized and what is the difference before and after the optimization?

[BiteTheDDDDt]

run buildall

[Copilot]

Pull request overview

This PR introduces a fixed-size, zlib-compatible CRC32 hashing fast path and wires it into vectorized column CRC updates to reduce hashing overhead for common primitive widths.

Changes:

• Add HashUtil::zlib_crc32_fixed() implementing a slicing-by-4 CRC32 for 1/2/4/8-byte values (fallback to zlib for other sizes).
• Refactor ColumnVector::update_crcs_with_value() to route through a new _zlib_crc32_hash() helper and use zlib_crc32_fixed() for non-date/datetime types.
• Adjust memcpy_fixed() to use memcpy and std::assume_aligned for aligned copies.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
be/src/vec/common/memcpy_small.h	Switch fixed-size copy helper to memcpy (with optional alignment hints).
be/src/vec/columns/column_vector.h	Declare new _zlib_crc32_hash() helper used by CRC batch updates.
be/src/vec/columns/column_vector.cpp	Refactor CRC batch update logic to use _zlib_crc32_hash() and zlib_crc32_fixed().
be/src/util/hash_util.hpp	Add zlib_crc32_fixed() slicing-by-4 implementation and use it for null hashing.

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[Copilot]

zlib_crc32_fixed is a function template and defines static constexpr CRC32SliceBy4Table tbl inside the template. This will instantiate (and potentially emit) a separate 4x256 CRC table for every distinct T used across the codebase, increasing compile time and binary size. Consider moving the slice-by-4 table to a non-templated shared singleton (e.g., an inline/constinit static in HashUtil, or a file-scope table) and have the template reuse it.

[hello-stephen]

BE UT Coverage Report

Increment line coverage 100.00% (64/64) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	52.71% (19451/36904)
Line Coverage	36.19% (181107/500370)
Region Coverage	32.60% (140719/431703)
Branch Coverage	33.62% (60950/181272)

[hello-stephen]

BE Regression && UT Coverage Report

Increment line coverage 100.00% (64/64) 🎉

Increment coverage report
Complete coverage report

Category	Coverage
Function Coverage	71.70% (25926/36159)
Line Coverage	54.30% (271041/499131)
Region Coverage	51.66% (225278/436083)
Branch Coverage	53.16% (96734/181976)

[BiteTheDDDDt]

run buildall

[BiteTheDDDDt]

run buildall

[BiteTheDDDDt]

run buildall