# Volume anomalies

The `elementary.volume_anomalies` test monitors the row count of your table over time per time bucket. If configured without a `timestamp_column`, it will count total table rows.

### How it works

1. Data is split into time buckets (daily by default, configurable with the `time_bucket` field).
2. Row count is computed per bucket for the last `training_period` days (14 days by default).
3. The test compares the row count of each bucket within the detection period (last 2 days by default, configured as `detection_period`) to the row count of previous time buckets.
4. The test only runs on completed time buckets. For example, with daily buckets, a test run in the middle of today would only count yesterday as a complete bucket.
5. If any anomalies are detected during the detection period, the test will fail.

### Configuration

{% tabs %}
{% tab title="Models" %}

```yml
models:
  - name: < model name >
    tests:
      - elementary.volume_anomalies:
          timestamp_column: < timestamp column >
          where_expression: < sql expression >
          time_bucket: # Daily by default
            period: < time period >
            count: < number of periods >
```

{% endtab %}

{% tab title="Models example" %}

```yml
models:
  - name: login_events
    config:
      elementary:
        timestamp_column: "loaded_at"
    tests:
      - elementary.volume_anomalies:
          where_expression: "event_type in ('event_1', 'event_2') and country_name != 'unwanted country'"
          time_bucket:
            period: day
            count: 1
          # optional - use tags to run elementary tests on a dedicated run
          tags: ["elementary"]
          config:
            # optional - change severity
            severity: warn

  - name: users
    # if no timestamp is configured, elementary will monitor without time filtering
    tests:
      - elementary.volume_anomalies:
          tags: ["elementary"]
```

{% endtab %}
{% endtabs %}

### Test configuration <a href="#test-configuration" id="test-configuration"></a>

No mandatory configuration, however it is highly recommended to configure a `timestamp_column`.

```yaml
tests:
  — elementary.volume_anomalies:
    timestamp_column: column name
    where_expression: sql expression
    anomaly_sensitivity: int
    anomaly_direction: [both | spike | drop]
    detection_period:
      period: [hour | day | week | month]
      count: int
    training_period:
      period: [hour | day | week | month]
      count: int
    time_bucket:
      period: [hour | day | week | month]
      count: int
    seasonality: day_of_week
    fail_on_zero: [true | false]
    ignore_small_changes:
      spike_failure_percent_threshold: int
      drop_failure_percent_threshold: int
    detection_delay:
      period: [hour | day | week | month]
      count: int
    anomaly_exclude_metrics: [SQL expression]
```