---
title: num_gaps() | Tiger Data Docs
description: Count the number of gaps between live ranges
---

Since [1.16.0](https://github.com/timescale/timescaledb-toolkit/releases/tag/1.16.0)

Return the number of gaps between the periods of liveness. Additionally, if the aggregate is not live at the start or end of its covered interval, these are also considered gaps.

## Samples

Given a table called `liveness` containing weekly heartbeat aggregates in column `health` with timestamp column `date`, use this query to see how many times the system was down in a particular week:

```
SELECT num_gaps(health)
FROM liveness
WHERE date = '01-9-2022 UTC'
```

Returns:

```
 num_gaps
---------
 4
```

## Arguments

The syntax is:

```
num_gaps(
    agg HEARTBEATAGG
) RETURNS BIGINT
```

| Name | Type         | Default | Required | Description                                          |
| ---- | ------------ | ------- | -------- | ---------------------------------------------------- |
| agg  | HeartbeatAgg | -       | ✔        | A heartbeat aggregate to get the number of gaps from |

## Returns

| Column    | Type   | Description                          |
| --------- | ------ | ------------------------------------ |
| num\_gaps | bigint | The number of gaps in the aggregate. |