Variable-length column store should support dictionaries, just like row-store does: this is mostly a code change in reconciliation, but it also requires a change to the on-page format because a dictionary cell on the page will now be a type-byte + an optional RLE + page-offset. Currently, row-store is overloading the flag in the type byte that says there's a 64B value in the cell to be the page-offset, and that will have to change: row-store dictionary cells will be type-byte + page-offset, column-store dictionary cells will be type-byte with 64B flag + RLE + page-offset.