Hi, On Wed, 24 Dec 2025 at 18:08, KAZAR Ayoub <[email protected]> wrote: > > Hello, > Following the same path of optimizing COPY FROM using SIMD, i found that COPY > TO can also benefit from this. > > I attached a small patch that uses SIMD to skip data and advance as far as > the first special character is found, then fallback to scalar processing for > that character and re-enter the SIMD path again... > There's two ways to do this: > 1) Essentially we do SIMD until we find a special character, then continue > scalar path without re-entering SIMD again. > - This gives from 10% to 30% speedups depending on the weight of special > characters in the attribute, we don't lose anything here since it advances > with SIMD until it can't (using the previous scripts: 1/3, 2/3 specials > chars). > > 2) Do SIMD path, then use scalar path when we hit a special character, keep > re-entering the SIMD path each time. > - This is equivalent to the COPY FROM story, we'll need to find the same > heuristic to use for both COPY FROM/TO to reduce the regressions (same > regressions: around from 20% to 30% with 1/3, 2/3 specials chars). > > Something else to note is that the scalar path for COPY TO isn't as heavy as > the state machine in COPY FROM. > > So if we find the sweet spot for the heuristic, doing the same for COPY TO > will be trivial and always beneficial. > Attached is 0004 which is option 1 (SIMD without re-entering), 0005 is the > second one.
Patches look correct to me. I think we could move these SIMD code portions into a shared function to remove duplication, although that might have a performance impact. I have not benchmarked these patches yet. Another consideration is that these patches might need their own thread, though I am not completely sure about this yet. One question: what do you think about having a 0004-style approach for COPY FROM? What I have in mind is running SIMD for each line & column, stopping SIMD once it can no longer skip an entire chunk, and then continuing with the next line & column. -- Regards, Nazir Bilal Yavuz Microsoft
