Struct Open 

pub struct Open {
    pub node: u32,
    pub seq: u64,
    pub sealed: Sealed,
}

A snapshot of the open, unsealed block: rows that have been acknowledged but not yet published, in the same Arrow shape the read path already knows.

This is the read-your-writes repair the write-ahead log made necessary (ARCHITECTURE section 4). With the log on, an export is acknowledged when its bytes reach the page cache, which is well before the block that will hold them is sealed and renamed into place — so without this, a client that just got a 200 and queried immediately would see nothing for up to max_block_age.

seq is the sequence the block will publish under, and that is what makes the whole thing cheap. A snapshot holds the builder’s rows from row zero, in the order they will be written, so row n of the snapshot is row n of the eventual block. A cursor handed out over open data is therefore still exactly correct after the seal, and the read path can drop the snapshot the moment a real block turns up under the same (node, seq) — no rebasing, no dedupe by content, no second identity for a row.

Fields

node: u32

seq: u64

sealed: Sealed