Re: Batching in executor

On Thu, Jan 29, 2026 at 8:35 AM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
>
> Hi,
>
> Here is v5 of the patch series.
>
> Patches 0001-0003 add the core batching infrastructure. 0001 adds the
> batch table AM API with heapam implementation, 0002 wires up SeqScan
> to use it (still returning one slot at a time), and 0003 adds EXPLAIN
> (BATCHES). I'd love to hear people's thoughts around TupleBatch
> structure added in 0002. I thought about making it a separate patch so
> that 0002 will still populate the single ScanState.ss_scanTupleSlot,
> but that means we'd still have to call the TAM callback to populate
> the tuple in the TAM's batch struct into the slot, defeating the whole
> point. With TupleBatch, you have executor_batch_rows number of slots
> which are filled in one TAM callback (materialize_all) call. So I
> decided to keep the TupleBatch and related things in 0002.
>
> For scans without quals, batching shows 20-30% improvement with no
> visible regressions when batching is disabled (batch_rows=0):
>
> SELECT * FROM t LIMIT n (no qual)
>
> Rows Master batch=0 %diff batch=64 %diff
> ------ -------- ------- ----- -------- -----
> 1M 12.42 ms 11.96 ms 3.7% 8.56 ms 31.0%
> 3M 38.95 ms 38.92 ms 0.1% 28.59 ms 26.6%
> 10M 153.64 ms 150.28 ms 2.2% 112.95 ms 26.5%
>
> (%diff: positive = faster than master, negative = slower)

Oops, I meant SELECT * FROM t LIMIT 1 OFFSET n (no qual).

--
Thanks, Amit Langote