Data warehouse/SQL alerts/Conditions

Conditions

Operators, ranges, warn levels, baseline comparisons and guards — one per column.

Each column of your result set can carry its own condition, with its own threshold, severity, alert and state.

Operators

Operators are words, not symbols.

Operator	Fires when	Needs
`gt`	value > threshold	One value
`gte`	value ≥ threshold	One value
`lt`	value < threshold	One value
`lte`	value ≤ threshold	One value
`eq`	value = threshold	One value
`neq`	value ≠ threshold	One value
`between`	threshold ≤ value ≤ max	Two values
`outside`	value < threshold or value > max	Two values

Important

between and outside need both ends. A band with one end set matches nothing — the rule saves cleanly and never fires. The editor marks a half-written band in red and refuses to leave it silently incomplete.

Which band do you want?

outside is the one most conditions actually want. A replication lag of 0 is as suspicious as one of 900 — it means the clock or the query is wrong, not that the mirror is perfect. A corridor catches both ends:

text

outside 1 … 60      →  fires below 1 and above 60
between 1 … 60      →  fires while the value sits inside the band

Comparison modes

A condition does not have to compare against a fixed number.

Mode	Compares	Use for
Absolute	The value itself	Most conditions
Delta %	Change since the last reading, as a percentage	Spikes and drops
Delta absolute	Change since the last reading	Counters
Ratio of	Value as a percentage of a baseline column	"actual vs expected"
Diff from	Value minus a baseline column	"how far behind are we"

Ratio and diff modes read the baseline from another column of the same row, which means the expectation is computed by your query and can be as clever as you like:

sql

SELECT
    subject,
    actual_so_far,
    expected_so_far,                                   -- the baseline
    round(100.0 * actual_so_far / expected_so_far, 1) AS pct_of_expected
FROM ...

Set the condition on actual_so_far with mode ratio of expected_so_far and a threshold of lt 70, and the alert says "412 against an expected 900" — both numbers, because "40% of expected" alone sends the reader to a dashboard before they can judge whether it matters.

Note

A change-based condition needs a previous reading. The first evaluation of a new rule records the value and does not fire — otherwise every such rule would alert on its first run, comparing against a zero that was never measured.

Warn levels

Most conditions support a warn threshold alongside the main one. The rule fires at warning when the value crosses the milder level, and escalates itself to the configured severity when it crosses the main one.

For ranges, the warn band must sit inside the critical band for outside, and outside it for between. The editor tells you when it does not — a warn level on the wrong side of the main threshold never fires.

Guards

Mark a condition a guard and it is evaluated before the measurements. If a guard fails, the measurements are not reported.

Use guards for anything that decides whether the data is worth believing:

sql

SELECT
    dateDiff('minute', max(_ingested_at), now()) AS mirror_lag_min,  -- guard: outside 0…30
    count()                                      AS rows_today,
    countIf(status='failed')                     AS failed            -- measurement
FROM warehouse.orders

A stale mirror then reports "the data is 4 hours old" instead of "failures fell to zero".

Per-condition severity and routing

Each condition has its own severity and its own alert. One query can raise a warning about volume and a critical about failures in the same run, and they recover independently.

Units and labels

Give a condition a unit (ms, %, min) and a label. The unit is appended to the value in messages; the label is what the alert calls it. A condition on p95_ms labelled "checkout latency" with unit ms produces "checkout latency is 812 ms (threshold ≥ 500)", which is a sentence.

Enabling and disabling

A condition can be disabled without deleting it. A disabled condition is not evaluated and does not hold state — useful while you are tuning a threshold and do not want the rule paging in the meantime.

Where this behaviour lives: backend/internal/domain/dwh_metrics.go. If the code and this page disagree, the code is right — please fix the page.

Part of Data warehouse — Querying the warehouse, and alerting on what the query returns.