> ## Documentation Index
> Fetch the complete documentation index at: https://developers.askparable.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Quality

> SPC, checks, and table health live at providers_quality.summary.* and per-table history sidecars.

Quality is a query catalog, not a fifth data pool. Provider tables in
[providers](/data/providers) hold the rows. Quality
holds measurements about those tables: statistical process control
(SPC), Gate 2 checks, shape stats, and catalog health.

Address the latest snapshot across the workspace, or the history of one
table:

| Surface                     | Address                                           | Use when                                             |
| --------------------------- | ------------------------------------------------- | ---------------------------------------------------- |
| Latest, all provider tables | `providers_quality.summary.{table}`               | Workspace-wide health, failing checks, SPC breaches. |
| History, one table          | `providers_quality.{connector}.{table}__{suffix}` | How a check or series changed over runs.             |

Only **main** provider tables get quality sidecars. Identity tables
(`providers.identity.*`), [artifacts](/data/artifacts),
and [parables](/data/parables) do not.

Run the SQL below over Flight SQL. Clients are on
[Querying the lake](/data#querying-the-lake).

## What each measurement is

**Checks** (Gate 2) compare a table to thresholds from the tap's quality
config and schema roles. Each row is one check on one table. Status is
`PASS`, `FAIL`, or `SKIPPED`. Skipped is not a pass -- the rule lacked a
required role (business key, event time, and so on) or window, so it
did not evaluate. Business-key columns are `x-transformDedupKey` on the
tap schema; see
[How taps project into tables](/connectors/tap-projection).

| Check ID                   | What it measures                                           |
| -------------------------- | ---------------------------------------------------------- |
| `null_rate`                | Required-column null rate vs `maxRate`.                    |
| `dupe_rate`                | Duplicate rate on business-key columns vs `maxRate`.       |
| `timestamp_coverage`       | Event-time values inside the expected window vs `minRate`. |
| `temporal_order`           | `effective_from` after `effective_to` vs `maxViolations`.  |
| `no_future_timestamp`      | Metadata timestamps in the future vs `maxViolations`.      |
| `timeline_gaps`            | Event-time gaps vs `maxGapDays`.                           |
| `string_pattern_rate`      | Values matching a pattern vs `maxRate`.                    |
| `referential_integrity`    | Orphan rate to a referenced column vs `maxOrphanRate`.     |
| `row_count_not_suspicious` | Row count is not one of the configured `suspiciousCounts`. |

Checks run when a table is promoted and again on a scheduled cadence.
The `lifecycle` column tells you which.

**SPC** is a Shewhart control chart on platform-owned series (row
count, column null percent, and similar). It is not a substitute for
the checks above. Each series has a rolling mean, standard deviation,
2-sigma warning limits, and 3-sigma control limits.

| Series status          | Meaning                                    |
| ---------------------- | ------------------------------------------ |
| `IN_BOUNDS`            | Latest point is inside the warning limits. |
| `WARNING`              | Outside 2-sigma, inside 3-sigma.           |
| `OUT_OF_BOUNDS`        | Outside the 3-sigma control limits.        |
| `INSUFFICIENT_HISTORY` | Fewer points than the configured minimum.  |

Tracked series kinds: `TABLE_ROW_COUNT`, `COLUMN_NULL_PCT`,
`COLUMN_VALIDATION_FAILURE_PCT`, `COLUMN_DISTINCT_COUNT`, `COLUMN_AVG`.

**Stats** are the shape snapshot each run uses (row count, column
count, bytes). **Health** is the catalog annotation for that table
(state, reason, watermark). Health is computed from annotations, not
from the same rollup path as checks and SPC.

## Latest across the workspace

Start here. These four tables are the current result per provider
table.

| Table                                      | Contents                           |
| ------------------------------------------ | ---------------------------------- |
| `providers_quality.summary.quality_checks` | Latest Gate 2 check per table.     |
| `providers_quality.summary.spc_results`    | Latest SPC series per table.       |
| `providers_quality.summary.table_stats`    | Latest row / column / byte counts. |
| `providers_quality.summary.table_health`   | Health state and watermark.        |

Failing checks for Google Workspace:

```sql theme={null}
SELECT
  connector,
  table_name,
  check_id,
  check_status,
  observed,
  threshold,
  comparator,
  captured_at
FROM providers_quality.summary.quality_checks
WHERE connector = 'google'
  AND check_status = 'FAIL'
ORDER BY captured_at DESC
```

`observed` is the measured rate or count. `threshold` is the configured
limit. `comparator` is how they were compared.

Every check that did not pass (fail or skip):

```sql theme={null}
SELECT
  connector,
  table_name,
  check_id,
  check_status,
  observed,
  threshold
FROM providers_quality.summary.quality_checks
WHERE check_status IN ('FAIL', 'SKIPPED')
ORDER BY connector, table_name, check_id
```

SPC series that have a warning, a control-limit breach, or recorded
violations:

```sql theme={null}
SELECT
  connector,
  table_name,
  series_id,
  series_kind,
  latest_value,
  mean,
  stddev,
  series_status,
  overall_status,
  captured_at
FROM providers_quality.summary.spc_results
WHERE has_violations = true
   OR series_status IN ('WARNING', 'OUT_OF_BOUNDS')
ORDER BY captured_at DESC
```

Largest provider tables by row count:

```sql theme={null}
SELECT
  connector,
  table_name,
  row_count,
  column_count,
  total_byte_size,
  captured_at
FROM providers_quality.summary.table_stats
ORDER BY row_count DESC
LIMIT 20
```

Stale watermarks:

```sql theme={null}
SELECT
  connector,
  table_name,
  health_state,
  health_reason,
  watermark,
  watermark_stale,
  computed_at
FROM providers_quality.summary.table_health
WHERE watermark_stale = true
```

## History for one table

Suffixes map to a result kind:

| Suffix     | History of                                                  |
| ---------- | ----------------------------------------------------------- |
| `__checks` | Gate 2 checks (one row per check per run).                  |
| `__spc`    | SPC series (one row per series per run).                    |
| `__stats`  | Shape stats.                                                |
| `__runs`   | Maintenance runs (compaction / vacuum), not quality scores. |

Google Workspace directory users:

```sql theme={null}
SELECT
  captured_at,
  check_id,
  check_status,
  observed,
  threshold,
  lifecycle,
  overall_status
FROM providers_quality.google.users__checks
ORDER BY captured_at DESC
LIMIT 20
```

How row-count SPC for that table moved:

```sql theme={null}
SELECT
  captured_at,
  series_id,
  series_kind,
  latest_value,
  mean,
  upper_control3_sigma,
  lower_control3_sigma,
  series_status
FROM providers_quality.google.users__spc
WHERE series_kind = 'TABLE_ROW_COUNT'
ORDER BY captured_at DESC
LIMIT 20
```

History tables keep every run. They also expose `result_id`, `run_id`,
`evidence_json` (checks), and `violations_json` (SPC) when you need the
payload behind a fail.

<Note>
  Older sidecar files may store status as `Fail` or `OutOfBounds`. Newer
  rows use `FAIL` and `OUT_OF_BOUNDS`. Summary tables go through typed
  decode and use the uppercase values. On `__checks` / `__spc`, filter
  both casings if a query comes back empty.
</Note>