ParquetSortKeyAttribute

Remarks

<para> The marker is opt-in on purpose. Both overloads are public API on the generated extension class, and emitting them for every eligible column would grow a wide model's surface by two methods per column whether or not anyone ever looks that column up. Declaring the lookup keys keeps the emitted API to the ones the model author actually wants. </para> <para> A marked member must be a flat, non-nullable root column of a totally ordered type whose Parquet statistics order matches <c>Comparer&lt;T&gt;.Default</c>: the integral types, <c>float</c>, <c>double</c>, or <see cref="DateTime"/>. Marking anything else is a compile-time error (PARQ014) rather than a silent no-op. <c>string</c> is deliberately excluded — Parquet orders <c>BYTE_ARRAY</c> statistics bytewise while <c>string.CompareTo</c> is culture-sensitive, so the two orders can disagree and pruning could drop matching rows. </para> <para> Marking a member changes nothing about the file that is written; pruning is a read-time optimisation that reads the footer statistics the writer already emits. It pays off only when the data is actually written in that column's order. </para>