Constant VERSION 

pub const VERSION: u16 = crate::format::SEGMENT_FORMAT_VERSION; // 1u16

Current segment format version.

v1 is the first format that exists. The layout changed several times before release; those generations were superseded before anyone could hold one, and their readers were deleted with them, so the count starts at the version that ships rather than at the number of edits it took to get there.

The version is checked for equality, not <=. Two layouts can differ in a way no tolerant reader bridges — one that named the time column timestamp against one that names it _time yields a batch whose time column nothing looks for, which is zero rows and no error — so a file this reader did not write is refused rather than guessed at.