Re: [PATCH 2/5] reftable/stack: add function to check if optimization is required

[Patrick Steinhardt <ps@pks.im>]

On Fri, Oct 31, 2025 at 03:22:22PM +0100, Karthik Nayak wrote:
> The reftable backend, performs auto-compaction as part of its regular

s/,//

> diff --git a/reftable/reftable-stack.h b/reftable/reftable-stack.h
> index d70fcb705d..a875149439 100644
> --- a/reftable/reftable-stack.h
> +++ b/reftable/reftable-stack.h
> @@ -123,6 +123,11 @@ struct reftable_log_expiry_config {
>  int reftable_stack_compact_all(struct reftable_stack *st,
>  			       struct reftable_log_expiry_config *config);
>  
> +/* Check if compaction is required. */
> +int reftable_stack_compaction_required(struct reftable_stack *st,
> +				       bool use_heuristics,
> +				       bool *required);
> +

I think the documentation here could be improved a bit. Somebody not
deeply familiar with reftables wouldn't know what `use_heuristics`
really is supposed to mean.

> diff --git a/reftable/stack.c b/reftable/stack.c
> index 49387f9344..18fa41cd5c 100644
> --- a/reftable/stack.c
> +++ b/reftable/stack.c
> @@ -1647,6 +1647,31 @@ static int stack_segments_for_compaction(struct reftable_stack *st,
>  	return 0;
>  }
>  
> +int reftable_stack_compaction_required(struct reftable_stack *st,
> +				       bool use_heuristics,
> +				       bool *required)
> +{
> +	struct segment seg;
> +	int err = 0;
> +
> +	if (st->merged->tables_len < 2) {
> +		*required = false;
> +		return 0;
> +	}
> +
> +	if (!use_heuristics) {
> +		*required = true;
> +		return 0;
> +	}
> +
> +	err = stack_segments_for_compaction(st, &seg);
> +	if (err)
> +		return err;
> +
> +	*required = segment_size(&seg) > 0;
> +	return 0;
> +}
> +

All of these conditions make sense.

Patrick