---
title: schema.fieldKeys() function
description: >
  `schema.fieldKeys()` returns field keys in a bucket.
menu:
  flux_v0_ref:
    name: schema.fieldKeys
    parent: influxdata/influxdb/schema
    identifier: influxdata/influxdb/schema/fieldKeys
weight: 301
flux/v0/tags: [metadata]
---

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`schema.fieldKeys()` returns field keys in a bucket.

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

**Note**: FieldKeys is a special application of `tagValues()` that returns field
keys in a given bucket.

##### 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
```

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

## Parameters

### bucket
({{< req >}})
Bucket to list field keys from.



### predicate

Predicate function that filters field 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 field keys from an InfluxDB bucket

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

schema.fieldKeys(bucket: "example-bucket")

```