StringBuilder.appendRepeated
void appendRepeated(scope const(char)[] value, size_t n) @safe pure nothrowAppends one string n times in one bulk pass (the unpivot amending ADR-2026-10-18-07: bulk producers live INSIDE the builder layer so hot paths never hand-assemble chunks). The payload tiles through copy-doubling, the offsets are arithmetic and the validity run is set in one call - byte-identical to n append calls, without the per-element header traffic (the unpivot variable column allocated ~100 MB through it at 2M rows).
Parameters
value | the string to repeat (an empty value repeats empty windows; use appendNull for null slots) |
n | the number of repetitions |