b26d254871
Adds a skill for authoring Tableau Next semantic models (SDMs) on Data 360: build from scratch, add data objects, define joins, enrich with calculated fields and metrics, and make models AI-ready. Smoke-tested against a live Data 360 org: SDM discovery, AI-readiness flip, dimension creation, metric creation, and description backfill all exercised end-to-end.
4.6 KiB
Empty-source handling
A data object can be "empty" for two very different reasons, and the right response differs. Authoring (a viz, a dashboard, a calc field, a metric) on either kind of empty source produces something that renders but shows nothing — the most expensive failure mode, because it looks like success. Diagnose which kind you have before building, and tell the user clearly.
Field-richness is not data-presence. An object can carry dozens of fields and
return zero rows. The field list proves the schema exists, not that data
does. Prove data presence by querying — python scripts/query_data.py --count <Object> — never by inspecting the field list.
The two empty states
1. Empty-of-rows (has fields, joinable, queries blank)
The object is fully defined: it has fields, it can participate in joins, a query against it succeeds — it just returns 0 rows.
- How it looks:
SELECT COUNT(*) FROM <object>→0. Schema/field discovery succeeds. No error. - What it means: the table exists and is materialized but currently holds no data (e.g. a filtered segment with no members yet, a freshly created DLO before its first ingest, a date-partitioned object with nothing in range).
- Response: treat as a real, query-confirmed empty. The data-presence gate
(
lib.query.assert_has_rows) hard-blocks here. Do not build on it; surface it (see User-facing wording below).
2. Unmaterialized / 0-field (cannot be joined; underlying table may not exist)
The object is declared but not actually backed by a queryable table.
- How it looks: discovery returns 0 fields, or a count query errors (rather than returning 0) — e.g. "table not found" / failed to resolve. It cannot be joined.
- What it means: the underlying physical table hasn't been created/populated yet. The object is a definition with nothing behind it.
- Response: this is indeterminate, not a confirmed 0-row count, so the gate warns rather than hard-blocks (a query failure must not be mistaken for a definite empty). Do not author on it — there is nothing to query. Resolve the upstream materialization first.
Distinguishing them quickly:
| Signal | Empty-of-rows | Unmaterialized / 0-field |
|---|---|---|
| Field discovery | returns fields | returns 0 fields |
COUNT(*) |
returns 0 (succeeds) |
errors (table not found) |
| Joinable? | yes | no |
| Gate behavior | hard-block (confirmed 0) | warn (indeterminate) |
DMO materialization is asynchronous — re-check before declaring empty
A DMO is empty until its DLO→DMO mapping materializes. After a mapping is
created (or data is freshly ingested), there is a lag before rows appear in the
DMO. A COUNT(*) of 0 immediately after mapping is expected and transient,
not a real empty.
- Before declaring a DMO empty, wait and re-check the count. If it goes from
0to non-zero, it was simply mid-materialization. - If it stays
0well past the expected materialization window, treat it as a genuine empty-of-rows (state 1) and surface it. - Discovery of the DLO→DMO mapping itself is the
data-cloud-connect-apiskill's job — use it to confirm a mapping exists before assuming the DMO will ever fill.
User-facing wording
When a build's sources come back empty, don't silently ship a blank result and don't silently pick a different source — tell the user what you found and offer a choice.
Some sources empty, others populated
"
<Object A>returned 0 rows, so a chart built on it would be blank.<Object B>and<Object C>have data (<n>and<m>rows). Want me to build the dashboard from the populated sources and drop<Object A>, or hold until<Object A>has data?"
Default: build from the populated sources, clearly noting which were dropped and why.
All sources empty
"Every source I checked for this dashboard returned 0 rows (
<Object A>: empty;<Object B>: empty). I can't build a meaningful dashboard on empty data — it would render 'No results to show' everywhere. This usually means either the data hasn't been ingested yet, or (for DMOs) the DLO→DMO mapping hasn't materialized. Do you want me to hold until data lands, or point me at a different, populated source?"
Default: stop and ask — do not proceed to a blank dashboard.
Unmaterialized source
"
<Object>isn't queryable yet (it has no fields / the table doesn't resolve), which usually means it hasn't been materialized. I can't author on it until the upstream data lands. Want me to use a different source, or check back after materialization?"