---
title: schema.tagKeys() function
description: schema.tagKeys() returns a list of tag keys for all series that match the predicate.
url: https://docs.influxdata.com/flux/v0/stdlib/influxdata/influxdb/schema/tagkeys/
estimated_tokens: 1355
product: Flux
version: v0
---

# schema.tagKeys() function

-   Flux 0.88.0+
-   View InfluxDB support

`schema.tagKeys()` returns a list of tag keys for all series that match the `predicate`.

Results include a single table with a single column, `_value`.

##### Function type signature

```js
(
    bucket: string,
    ?predicate: (
        r: {
            A with
            _value: B,
            _time: time,
            _stop: time,
            _start: time,
            _measurement: string,
            _field: string,
        },
    ) => bool,
    ?start: C,
    ?stop: D,
) => stream[E] where E: Record
```

For more information, see [Function type signatures](/flux/v0/function-type-signatures/).

## Parameters

### bucket

(Required) Bucket to return tag keys from.

### predicate

Predicate function that filters tag keys. Default is `(r) => true`.

### start

Oldest time to include in results. Default is `-30d`.

### stop

Newest time include in results. The stop time is exclusive, meaning values with a time equal to stop time are excluded from the results. Default is `now()`.

Relative start times are defined using negative durations. Negative durations are relative to `now()`. Absolute start times are defined using time values.

## Examples

### Query tag keys in an InfluxDB bucket

```js
import "influxdata/influxdb/schema"

schema.tagKeys(bucket: "example-bucket")
```

#### Not supported in the Flux REPL

`schema` functions can retrieve schema information when executed within the context of InfluxDB, but not from the [Flux REPL](/influxdb/cloud/tools/repl/).

#### Related

-   [Explore your data schema with Flux](/influxdb/v2/query-data/flux/explore-schema/)
-   [SHOW TAG KEYS in InfluxQL](/influxdb/v1/query_language/explore-schema#show-tag-keys)

[metadata](/flux/v0/tags/metadata/)