DDSketch maintenance rejects 0 and negative inputs that asap_sketchlib supports #527

Problem

DDSketchAccumulatorUpdater::validate_single_input (crates/asap-physical-operators/src/summary_kernels/factory.rs:140) accepts only values that are finite, > 0.0, and within [min_indexable, max_indexable]. Everything else fails with "DDS maintenance input is outside its positive representable domain".

build_summary (operators/summary/mod.rs:445) propagates that error with ?, so a single 0 sample fails the whole summary update. Downstream in ASAPQuery-backend, this permanently breaks the DDS worker until it is restarted (ProjectASAP/ASAPQuery-backend#773). Real metrics contain zeros all the time. In the network-control demo, idle tasks report network_mbps = 0.

Why the check can go

The pinned asap_sketchlib (5f03ccbd, and current main) handles the full signed domain in DDSketch::try_add:

• 0 and magnitudes below min_indexable go to zero_count
• negative values go to negative_store
• the only rejections are non-finite values and |v| > max_indexable, and try_add reports those as errors itself

So the planner-side check is stricter than the sketch, and it rejects valid input.

Proposal

Relax the check to match sketchlib, i.e. value.is_finite() && value.abs() <= maximum, or call try_add and map its error. Add a test showing that 0, negative, and sub-min_indexable inputs are accepted and that quantiles over them are correct.

The quantile-ratio certificate (quantile_input_domain, see #446) needs a denominator domain that excludes zero. That is a planning-time property, separate from maintenance, and per-sample validation should not enforce it.