CoollZzz opened a new pull request, #123:
URL: https://github.com/apache/iotdb-extras/pull/123
## Description
This PR improves Grafana table-model queries by supporting custom legend
formats and returning Grafana's native `No data` state when a time-series
result contains no plottable values.
### Support Grafana `legendFormat`
- Adds `legendFormat` to the frontend query model, table-model query editor,
and backend query parameters.
- Supports static legends and templates such as `{{instance}}` and
`{{nodeType}} - {{nodeId}}`.
- Resolves legend templates after converting long-form query results to wide
time-series frames, when the per-series labels are available.
- Maps common Prometheus label names to their IoTDB column aliases, such as
`nodeType` to `node_type` and `name` to `label_name`.
- Leaves the legend unchanged when `legendFormat` is empty or set to
Grafana's `__auto` sentinel.
- Applies the resolved value through `DisplayNameFromDS` without overwriting
other field configuration.
Resolving legends in the backend keeps imported Prometheus dashboards
compatible and avoids requiring panel-specific field overrides.
### Show `No data` for empty time-series results
Some IoTDB `HOP` and `rate` queries return timestamped rows whose numeric
values are all `NULL`, instead of returning zero rows. Grafana previously
received a non-empty frame for these results and rendered empty axes rather
than its `No data` state.
This PR treats a time-series result as having no plottable data when:
- the result contains zero rows; or
- every numeric value column contains only `NULL` values.
In these cases, the backend returns no frame, allowing Grafana to display
`No data`.
The behavior is limited to the `Time series` format. The `Table` format
still returns a frame so that column headers and `NULL` rows remain available
to table panels. This logic is implemented in the plugin instead of adding
query-specific SQL filters, so it also applies to future sparse aggregation
queries.
### Testability and coverage
The table query execution path is separated from response construction
through `executeTableQuery`. Tests can replace the query runner with an
in-memory result, allowing response semantics to be tested without a live IoTDB
RPC service.
Added coverage includes:
- static and templated legend formats;
- multiple placeholders and whitespace handling;
- Prometheus-to-IoTDB label aliases;
- missing and empty labels;
- the empty and `__auto` no-op formats;
- preservation of existing field configuration;
- legend application after long-to-wide conversion;
- zero-row time-series and table results;
- all-`NULL` numeric time-series results;
- partially populated numeric results; and
- `legendFormat` query deserialization and backward compatibility.
### Testing
- `go test -count=1 ./...`
- `go vet ./...`
- `npm run typecheck`
- `npm run test:ci`
- `npm run build`
- `git diff upstream/master --check`
<hr>
This PR has:
- [x] been self-reviewed.
- [x] added comments explaining the intent of non-obvious behavior.
- [x] added unit tests covering the new code paths.
- [ ] been tested in a test IoTDB cluster.
<hr>
##### Key changed/added classes (or packages if there are too many classes)
in this PR
- `connectors/grafana-plugin/pkg/plugin/table_query.go`
- `connectors/grafana-plugin/pkg/plugin/table_query_test.go`
- `connectors/grafana-plugin/pkg/plugin/plugin.go`
- `connectors/grafana-plugin/src/QueryEditor.tsx`
- `connectors/grafana-plugin/src/types.ts`
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