2 ms·
The difference is in the operations. With a b tree the software operates on 1 row at a time, but when represented as a series of bit, then in a 32 bit CPU you c
by jorgeleo 15y ago
The difference is in the operations. With a b tree the software operates on 1 row at a time, but when represented as a series of bit, then in a 32 bit CPU you can process 32 rows in 1 instruction. Which leads to bitmap index over GPU...
- nivertech 15y agoIt will be 64bit at a time using plain CPU instruction or 128-512bits at a time using SIMD or GPU. Also article describes a word-aligned bitmaps data structure, which uses RLE, so it will skip areas of all-zeros or all-ones.
- jorgeleo 15y agoYes, the only problem I found when writing my own bitmap index is they become cumbersome when asking the question: what value has this column for this row. RLE does not help there. But they are extremely fast when asking the question: what rows has this value on this column. And that is the whole concept, the ability to flip the question.