issue: #45486
This commit refactors the chunk writing system by introducing a
two-phase
approach: size calculation followed by writing to a target. This enables
efficient group chunk creation where multiple fields share a single mmap
region, significantly reducing the number of mmap system calls and VMAs.
- Optimize `mmap` usage: single `mmap` per group chunk instead of per
field
- Split ChunkWriter into two phases:
- `calculate_size()`: Pre-compute required memory without allocation
- `write_to_target()`: Write data to a provided ChunkTarget
- Implement `ChunkMmapGuard` for unified mmap region lifecycle
management
- Handles `munmap` and file cleanup via RAII
- Shared via `std::shared_ptr` across multiple chunks in a group
Signed-off-by: Shawn Wang <shawn.wang@zilliz.com>
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Signed-off-by: Shawn Wang <shawn.wang@zilliz.com>
4b14ab14e3