Too Long; Didn't Read
Halo2 uses permutation argument technology to allow copy constraint on any number of columns. The algorithm mentioned in the Halo2 book is a little bit obscure. We will discuss the equality property between the elements of multiple columns of data on the table (2krows, index starts from 0), that is, copy constraint. The combination algorithm can refer to the details of the Algorithm in the book. For the main branch of the corresponding Halo2 code, commit is: a7cd600eb60b1528159b92af5e426adcc615de1a.