Function fnv1a 

pub fn fnv1a(bytes: &[u8]) -> u64

FNV-1a-64 hash with a fixed seed (cross-process deterministic). Used to fingerprint an Arrow IPC schema block so a schema-less batch can be matched to the schema it was encoded against (see SCHEMA_HASH). The producer node, the consumer node, and the daemon’s dora topic debug path all hash the same schema-block bytes with this function, so the value must stay identical across crates — keep this the single source of truth.