﻿---
title: ES|QL FORK command
description: 
url: https://www.elastic.co/elastic/docs-builder/docs/2890/reference/query-languages/esql/commands/fork
products:
  - Elasticsearch
---

# ES|QL FORK command
<applies-to>
  - Elastic Cloud Serverless: Preview
  - Elastic Stack: Preview since 9.1
</applies-to>

The `FORK` processing command creates multiple execution branches to operate
on the same input data and combines the results in a single output table.

## Syntax

```esql
FORK ( <processing_commands> ) ( <processing_commands> ) ... ( <processing_commands> )
```


## Description

The `FORK` processing command creates multiple execution branches to operate
on the same input data and combines the results in a single output table. A discriminator column (`_fork`) is added to identify which branch each row came from.
Together with the [`FUSE`](https://www.elastic.co/elastic/docs-builder/docs/2890/reference/query-languages/esql/commands/fuse) command, `FORK` enables hybrid search to combine and score results from multiple queries. To learn more about using ES|QL for search, refer to [ES|QL for search](https://docs-v3-preview.elastic.dev/elastic/docs-builder/docs/2890/solutions/search/esql-for-search).
<note>
  `FORK` branches default to `LIMIT 1000` if no `LIMIT` is provided.
  In a future release, no implicit `LIMIT` will be added to `FORK` branches.
  To maintain the current behavior of the queries using `FORK`, it is recommended
  to include a `LIMIT` in each `FORK` branch.
</note>


## Output behavior

`FORK` merges its branch outputs into a single table, adding a `_fork` discriminator
column to each row to indicate which branch it came from.

### Branch identification

The `_fork` column takes values like `fork1`, `fork2`, `fork3`, corresponding to the
order branches are defined.

### Column handling

Branches can output different columns. Columns with the same name must have the same
data type across all branches; missing columns are filled with `null` values.

### Row ordering

Row order is preserved within each branch, but rows from different branches may be
interleaved. Use `SORT _fork` to group results by branch.

## Limitations

- `FORK` supports at most 8 execution branches.
- In versions older than 9.3.0 using remote cluster references and `FORK` is not supported.
- Using more than one `FORK` command in a query is not supported.


## Examples

The following examples show how to run parallel branches and combine their results.

### Run two branches and identify rows by branch

Each `FORK` branch returns one row. `FORK` adds a `_fork` column that indicates
which branch each row came from:
```esql
FROM employees
| FORK ( WHERE emp_no == 10001 )
       ( WHERE emp_no == 10002 )
| KEEP emp_no, _fork
| SORT emp_no
```


| emp_no:integer | _fork:keyword |
|----------------|---------------|
| 10001          | fork1         |
| 10002          | fork2         |


### Return row count alongside top results

Returns the total number of rows that match the query along with
the top five rows sorted by score:
```esql
FROM books METADATA _score
| WHERE author:"Faulkner"
| EVAL score = round(_score, 2)
| FORK (SORT score DESC, author | LIMIT 5 | KEEP author, score)
       (STATS total = COUNT(*))
| SORT _fork, score DESC, author
```


| author:text      | score:double | _fork:keyword | total:long |
|------------------|--------------|---------------|------------|
| Colleen Faulkner | 2.18         | fork1         | null       |
| William Faulkner | 2.18         | fork1         | null       |
| Danny Faulkner   | 2.02         | fork1         | null       |
| Paul Faulkner    | 2.02         | fork1         | null       |
| William Faulkner | 2.02         | fork1         | null       |
| null             | null         | fork2         | 18         |