alt Hacker NewsAlmost literally what I stated. Consider a row in Postgres table or similar. Convert the entire WHERE clause across all columns in that table into a very short sequence of SIMD instructions against the same memory. All of the columns, regardless of type, are evaluated simultaneously using SIMD. For many complex constraints you can match rows in single digit clock cycles even across many unrelated types. This is much faster than using secondary indexes in many cases.
It isn’t hypothetical, I’ve shipped systems that worked this way. You can match search patterns across a random dozen columns across a schema of hundreds of columns at essentially full memory bandwidth.
OK, I thought it couldn't be that, because that should be doable with std::simd or a SIMD abstraction. Well, unless you JIT it, in which case intrinsics wouldn't help either.
> You can match search patterns across a random dozen columns across a schema of hundreds of columns at essentially full memory bandwidth
Do I underatand it correctly, that this would only work, if you have multiple of the same comparisons (e.g. equality check with same sized data) in the WHERE clause and the relevant collumns are within one multiple of the SIMD width of each other?