feat: Introduce new summary section for data metrics#47
Draft
Moritz Potthoff (MoritzPotthoffQC) wants to merge 8 commits into
Draft
feat: Introduce new summary section for data metrics#47Moritz Potthoff (MoritzPotthoffQC) wants to merge 8 commits into
Moritz Potthoff (MoritzPotthoffQC) wants to merge 8 commits into
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## main #47 +/- ##
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- Coverage 100.00% 99.64% -0.36%
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Files 14 14
Lines 1052 1117 +65
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+ Hits 1052 1113 +61
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Copilot started reviewing on behalf of
Moritz Potthoff (MoritzPotthoffQC)
July 17, 2026 12:09
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Pull request overview
This PR extends Diffly’s summary reporting to distinguish change metrics (computed over deltas) from data inspection metrics (describing left/right datasets), and renders the latter in a new dedicated “Data Inspection” section while also separating them in the JSON schema.
Changes:
- Add
Metric.kind("change"vs"data") and mark theNull%preset as a"data"metric. - Split per-column metric outputs into
metricsvsdata_metricsin the summary JSON, and render"data"metrics in a new “Data Inspection” section. - Update summary tests and regenerate pretty-output fixtures to reflect the new section/layout.
Reviewed changes
Copilot reviewed 36 out of 36 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| diffly/metrics/_common.py | Adds Metric.kind to classify metrics by rendering section. |
| diffly/metrics/data.py | Marks Null% preset as a "data" metric. |
| diffly/summary.py | Routes metric labels into change vs data lists; adds “Data Inspection” rendering and JSON schema changes. |
| tests/summary/test_summary.py | Adds coverage for metrics vs data_metrics JSON routing; updates expected JSON shape. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_True_top_True_slim_True_sample_rows_True_sample_pk_True.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_True_top_True_slim_True_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_True_top_True_slim_False_sample_rows_True_sample_pk_True.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_True_top_True_slim_False_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_True_top_False_slim_True_sample_rows_True_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_True_top_False_slim_True_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_True_top_False_slim_False_sample_rows_True_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_True_top_False_slim_False_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_False_top_True_slim_True_sample_rows_True_sample_pk_True.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_False_top_True_slim_True_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_False_top_True_slim_False_sample_rows_True_sample_pk_True.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_False_top_True_slim_False_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_False_top_False_slim_True_sample_rows_True_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_False_top_False_slim_True_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_False_top_False_slim_False_sample_rows_True_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_True_perfect_False_top_False_slim_False_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_True_top_True_slim_True_sample_rows_True_sample_pk_True.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_True_top_True_slim_True_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_True_top_True_slim_False_sample_rows_True_sample_pk_True.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_True_top_True_slim_False_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_True_top_False_slim_True_sample_rows_True_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_True_top_False_slim_True_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_True_top_False_slim_False_sample_rows_True_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_True_top_False_slim_False_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_False_top_True_slim_True_sample_rows_True_sample_pk_True.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_False_top_True_slim_True_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_False_top_True_slim_False_sample_rows_True_sample_pk_True.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_False_top_True_slim_False_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_False_top_False_slim_True_sample_rows_True_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_False_top_False_slim_True_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_False_top_False_slim_False_sample_rows_True_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
| tests/summary/fixtures/metrics_null_fraction/gen/pretty_False_perfect_False_top_False_slim_False_sample_rows_False_sample_pk_False.txt | Updates fixture output to move Null% into “Data Inspection”. |
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Moritz Potthoff (MoritzPotthoffQC)
marked this pull request as ready for review
July 17, 2026 13:56
Moritz Potthoff (MoritzPotthoffQC)
requested review from
EgeKaraismailogluQC,
Marius Merkle (MariusMerkleQC) and
Oliver Borchert (borchero)
as code owners
July 17, 2026 13:56
EgeKaraismailogluQC
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EgeKaraismailogluQC
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Thank you Moritz Potthoff (@MoritzPotthoffQC)! In general I am happy with the layout. I added a few comments. In addition to those, I think it would be nice to have at least one summary fixture where we render two or more data metrics rather than just one, just to see what that looks like (maybe I missed it?).
| @@ -716,6 +749,7 @@ class SummaryDataColumn: | |||
| n_total_changes: int | |||
| changes: list[SummaryDataColumnChange] | None | |||
| metrics: dict[str, Any] | None | |||
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?
Suggested change
| metrics: dict[str, Any] | None | |
| change_metrics: dict[str, Any] | None |
Comment on lines
+18
to
+20
| ``kind`` selects the summary section the metric is rendered in: ``"change"`` metrics | ||
| appear as columns in the "Columns" table, while ``"data"`` metrics get their own | ||
| "Data Inspection" section. |
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I think it could be nicer to also explain the semantic difference between change metrics and data metrics. Right now, it sounds like the only difference is where it gets rendered, but the underlying reason for why we present these two options is not clear.
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| fn: MetricFn | ||
| selector: cs.Selector | ||
| kind: Literal["change", "data"] = "change" |
Collaborator
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I think it could be good to not provide a default here to force the user to think about what kind of metric they implemented. Wdyt?
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Also, nothing prevents me from "registering" a change metric as a data metric and vice versa. Going a step further, I wish there was a way to infer kind from the type of fn automatically. Right now that does not work of course since both change metrics and data metrics are the same type. Something along these lines:
DataMetricFn = Callable[[pl.Expr], pl.Expr]and then rewrite:
def null_fraction_change(col: pl.Expr) -> pl.Expr:
return col.is_null().mean()
class Metric:
fn: ChangeMetricFn | DataMetricFn
#(property)
def kind(self) -> str:
return "data" if isinstance(DataMetricFn, self.fn) else "change"Metric would then also need to wrap .fn if it is a DataMetricFn to make it have the same interface. Could you follow my idea? Wdyt?
| from ._common import Metric, MetricFn | ||
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| def _make_data_metric(fn: MetricFn, selector: cs.Selector = cs.all()) -> Metric: |
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IMO this partial method does not add a lot of value, so it could be dropped. We could just add the kind parameter below in DEFAULT_DATA_METRICS. Wdyt?
Moritz Potthoff (MoritzPotthoffQC)
marked this pull request as draft
July 22, 2026 17:29
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Motivation
See this discussion: We want to display
datametrics in their own section in the summary.Changes
Data Inspectionthat gets all the data metrics