[serprex]

WAL replay sent rows to batcher one at a time, adding channel overhead
for every row. Bootstrap already grouped rows into chunks.

Share bootstrap row buffer with WAL replay and allow chunks to span
transactions. Register transactions before sending rows, then report
row counts afterward so acknowledgments cannot arrive too early.

Flush buffered rows at size limits, input boundaries, idle, completion,
and errors. Send rows holding detoast memory permits immediately so
buffered memory cannot block later allocations. Keep failed transactions
incomplete so acknowledgments cannot advance past them.

Depends on #265.

Validation: cargo fmt --all -- --check, cargo clippy --workspace --all-targets --locked -- -D warnings, RUSTDOCFLAGS=-D warnings cargo doc --no-deps --lib --bins, full cargo nextest run --workspace --all-targets --locked against PG 17.

🤖 Generated with Claude Code

[serprex]

WalReplaySink::on_record(COMMIT) over synthetic inline Int4 rows into tail::spawn_null. Release, Rust 1.99.1, Ryzen 7 7840U, taskset -c 2,4,6, median total of 7 runs.

Parent 0cfa6db, 568d6b6 (prior push), a610259 (seqs held across commits, rows ship on buffer trigger, segment boundary, finish, or error).

Rows/commit	Int4 columns	Commits	Parent ms	568d6b6 ms	a610259 ms	a610259 vs parent
1	8	262,144	363	389	210	1.73×
32	8	32,768	387	292	240	1.61×
64	8	16,384	373	285	231	1.61×
1,024	8	1,024	362	235	223	1.62×
16,384	8	64	360	242	255	1.41×
1,024	64	1,024	588	431	414	1.42×
262,144	8	1	98	65	67	1.47×

16,384×64 reruns at 11 samples: 238–244 ms, noise.

cargo bench --bench wal_replay -- --rows 1 --transactions 262144 --columns 8 --repeats 7