[Issue #493] Align the location of column byte buffer in pxl file. #495
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bianhq
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Jul 14, 2023
pixels-core/src/main/java/io/pixelsdb/pixels/core/PixelsWriterImpl.java
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Unaligned read causes error for SIMD instructions. For example, is the address of a long column vector is 0x0c, it would have unalign read (the address should be the multiple of 8). In the normal instruction it would affect the performance adversely, but we don't know how much performance degrade would happen, but at least here is no correctness issue. However, if we use SIMD, the unalign read is erroneous, so we have to fix it.
We add a parameter in pixels.properties so that we can adjust the alignment value. The default one is 32. It is aligned for avx2(256 bit) SIMD instruction.
Closes #493.