---
title: "list_reverse"
slug: "dev-database-reference-sql-functions-lists-list-reverse"
updated: 2026-10-30T18:19:11Z
published: 2026-10-30T18:19:11Z
canonical: "docs.vastdata.com/dev-database-reference-sql-functions-lists-list-reverse"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.vastdata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# list_reverse

*Applies to VAST Cluster 5.5.*

*[Functions](/develop/docs/dev-database-reference-sql-functions-index) › [List, struct and map functions](/develop/docs/dev-database-reference-sql-functions-lists-and-structs) › Combine and change lists.* Returns the elements of a list in reverse order. `array_reverse` is the same function.

## Syntax

```
list_reverse(list)
array_reverse(list)
```

| Argument | Type | Description |
| --- | --- | --- |
| `list` | A list of any type | The list to reverse. |

**Returns:** a list of the same type.

**Aliases:** `array_reverse`.

## Set up the examples

The examples connect with the ADBC driver, as in [VAST Query Engine (ADBC)](/develop/docs/dev-database-integrations-adbc), and work in a schema called `docs_sql_fn_lists_list_reverse`. Set `QE_ENDPOINT`, `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY` and `VASTDB_BUCKET` ([SQL reference](/develop/docs/dev-database-reference-sql-index#example-connect-and-use-a-transaction)), and run the blocks in order in one Python session. Below each block is the output you should see.

This block connects, defines the `run()` and `plan()` helpers, and creates a table of four routes, each with a list of stops (`stops`, in travel order) and a list of distances (`legs`). Route 2 has a NULL stop, route 3 has empty lists, and route 4 has no values:

```
import os
import re

import adbc_driver_manager
import adbc_driver_manager.dbapi as dbapi
import adbc_driver_vastdb

BUCKET = os.environ["VASTDB_BUCKET"]
SCHEMA = f'"{BUCKET}/docs_sql_fn_lists_list_reverse"'

conn = dbapi.connect(
    driver=adbc_driver_vastdb.get_driver_path(),
    db_kwargs={
        "vast.db.endpoint": os.environ["QE_ENDPOINT"],
        "vast.db.access_key": os.environ["AWS_ACCESS_KEY_ID"],
        "vast.db.secret_key": os.environ["AWS_SECRET_ACCESS_KEY"],
    },
    autocommit=True,
)

def server_message(e):
    """The server's message in a driver error, without the request ID or the echoed statement."""
    text = re.sub(r"\[req=0x[0-9a-f]+\]: ", "", str(e))
    found = (re.search(r'message: "(.*?)", request_id', text, re.S)
             or re.search(r"description: (.*)\)", text, re.S))
    message = found.group(1) if found else text.strip().splitlines()[-1]
    message = re.sub(r"^Plan query: '.*?' failed with: ", "", message, flags=re.S)
    message = re.split(r"\\n|\n", message)[0].replace('\\"', '"')
    return message.replace(BUCKET, "<bucket>")

def run(sql):
    """Run one statement. Print the rows it returns, or the error."""
    try:
        with conn.cursor() as cur:
            cur.execute(sql)
            rows = cur.fetchall() if cur.description else []
    except (adbc_driver_manager.Error, OSError) as e:
        print(f"{type(e).__name__}: {server_message(e)}")
    else:
        print(rows)

def plan(sql):
    """Print the plan without its ~N Rows lines: the table's row count, which can still be 0 just after an insert."""
    with conn.cursor() as cur:
        cur.execute("EXPLAIN " + sql)
        steps = cur.fetchall()[0][1]
    print("\n".join(line for line in steps.splitlines() if "Rows" not in line))

TABLE = f"{SCHEMA}.routes"
run(f"CREATE SCHEMA IF NOT EXISTS {SCHEMA}")
run(f"CREATE TABLE IF NOT EXISTS {TABLE} (id BIGINT, stops VARCHAR[], legs DOUBLE[])")
run(f"INSERT INTO {TABLE} VALUES "
    "(1, ['depot', 'mill', 'port'], [0.5, 2.5, 4.0]), "
    "(2, ['port', NULL, 'depot'], [2.0, 1.0]), "
    "(3, [], []), "
    "(4, NULL, NULL)")
```

```
[]
[]
[(4,)]
```

## What it does

`list_reverse` returns the same elements, last first: `list_reverse([1, 2, 3])` is `[3, 2, 1]`. It doesn't sort: NULL elements and repeated values stay where they are, counted from the other end. `list_reverse([1, NULL, 3])` is `[3, NULL, 1]`.

On a list of lists, only the outer list is reversed: `list_reverse([[1, 2], [3]])` is `[[3], [1, 2]]`.

It takes lists only. To reverse a string, use [reverse](/develop/docs/dev-database-reference-sql-functions-string-reverse).

## NULLs and edge cases

| Input | Result |
| --- | --- |
| `NULL` | `NULL` |
| `[]` | `[]` |
| `[1, NULL, 3]` | `[3, NULL, 1]` |
| `[[1, 2], [3]]` | `[[3], [1, 2]]` |
| `array_value(1, 2)` (a fixed-size array) | `[2, 1]` |
| A `VARCHAR` or `BLOB` | Error: `Not implemented Error: Slice with steps has not been implemented for string types` |
| A number, date or boolean | Error: `ARRAY_SLICE can only operate on LISTs and VARCHARs` |

The same cases, as the cluster returns them. They use the helpers from [Set up the examples](/develop/docs/dev-database-reference-sql-functions-lists-list-reverse#set-up-the-examples):

```
run("SELECT list_reverse(NULL), list_reverse([]), list_reverse([1, NULL, 3]), list_reverse([[1, 2], [3]]), "
    "list_reverse(array_value(1, 2))")
run("SELECT list_reverse('abc')")
run("SELECT list_reverse(123)")
```

```
[(None, [], [3, None, 1], [[3], [1, 2]], [2, 1])]
InternalError: Not implemented Error: Slice with steps has not been implemented for string types, you can consider rewriting your query as follows:
InternalError: Binder Error: ARRAY_SLICE can only operate on LISTs and VARCHARs
```

## Examples

Each route's stops and distances for the way back. Route 2's NULL stop stays in the middle:

```
run(f"SELECT id, list_reverse(stops), array_reverse(legs) FROM {TABLE} ORDER BY id LIMIT 10")
```

```
[(1, ['port', 'mill', 'depot'], [4.0, 2.5, 0.5]), (2, ['depot', None, 'port'], [1.0, 2.0]), (3, [], []), (4, None, None)]
```

The last stop of each route is the first element of the reversed list:

```
run(f"SELECT id, list_reverse(stops)[1] FROM {TABLE} ORDER BY id LIMIT 10")
```

```
[(1, 'port'), (2, 'depot'), (3, None), (4, None)]
```

Find the routes whose way back is `port`, `mill`, `depot`:

```
run(f"SELECT id FROM {TABLE} WHERE list_reverse(stops) = ['port', 'mill', 'depot'] ORDER BY id LIMIT 10")
```

```
[(1,)]
```

## How it runs in VAST

The Query Engine runs on the cluster's CNodes, and a query on a table starts with a scan in VAST DataBase (`VAST_SCAN`). The scan reads a list column whole, and VAST DataBase doesn't evaluate list functions, so `list_reverse()` is always computed by the Query Engine:

- **In the `SELECT` list,** the scan reads the list column and the Query Engine computes `list_reverse()` for each row it returns.
- **In `WHERE`,** the scan sends the list for every row, and a `FILTER` step in the Query Engine computes the condition and keeps the rows that match. No rows are skipped in storage.

The plan of the `WHERE` example shows the `FILTER` step above the scan:

```
plan(f"SELECT id FROM {TABLE} WHERE list_reverse(stops) = ['port', 'mill', 'depot']")
```

```
┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│ (array_slice(stops, [], []│
│ , -1) = ['port', 'mill',  │
│         'depot'])         │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│           stops           │
│             id            │
│                           │
└───────────────────────────┘
```

## Make it faster

- **Compare with a reversed constant instead.** `list_reverse(stops) = [&apos;port&apos;, &apos;mill&apos;, &apos;depot&apos;]` is the same as `stops = [&apos;depot&apos;, &apos;mill&apos;, &apos;port&apos;]`, which saves reversing every row's list. A condition on a list still runs in a `FILTER` step either way:

```
plan(f"SELECT id FROM {TABLE} WHERE stops = ['depot', 'mill', 'port']")
```

```
┌───────────────────────────┐
│         PROJECTION        │
│    ────────────────────   │
│             #1            │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│           FILTER          │
│    ────────────────────   │
│ (stops = ['depot', 'mill',│
│          'port'])         │
│                           │
└─────────────┬─────────────┘
┌─────────────┴─────────────┐
│         VAST_SCAN         │
│    ────────────────────   │
│    Function: VAST_SCAN    │
│                           │
│        Projections:       │
│           stops           │
│             id            │
│                           │
└───────────────────────────┘
```

- **Take the last element directly.** `stops[-1]` or [list_last](/develop/docs/dev-database-reference-sql-functions-lists-list-last) returns the last element without building a reversed list.
- **Pair a list condition with a pushed-down condition** on a plain column, such as `id &gt; 1`, so the list condition runs only on the rows that pass it.

## Limitations and errors

- **Lists only.** A `VARCHAR` or `BLOB` fails with `Not implemented Error: Slice with steps has not been implemented for string types`; use [reverse](/develop/docs/dev-database-reference-sql-functions-string-reverse) for a string. A number, date or boolean fails with `ARRAY_SLICE can only operate on LISTs and VARCHARs`.
- **Not a sort.** To order the elements from largest to smallest, use [list_reverse_sort](/develop/docs/dev-database-reference-sql-functions-lists-list-reverse-sort) or `list_sort(l, &apos;DESC&apos;)`.
- **One level.** Inner lists keep their order. To reverse them too, apply it to each: `list_transform(l, x -&gt; list_reverse(x))`.

```
run("SELECT reverse('abc'), list_transform([[1, 2], [3]], x -> list_reverse(x))")
```

```
[('cba', [[2, 1], [3]])]
```

## Similar functions

| Function | Result for `[3, 1, NULL, 3, 10]` |
| --- | --- |
| `list_reverse(l)` | `[10, 3, NULL, 1, 3]` |
| [list_reverse_sort](/develop/docs/dev-database-reference-sql-functions-lists-list-reverse-sort): sorts, largest first | `[10, 3, 3, 1, NULL]` |
| [list_sort](/develop/docs/dev-database-reference-sql-functions-lists-list-sort) with `&apos;DESC&apos;` | `[10, 3, 3, 1, NULL]` |
| [list_sort](/develop/docs/dev-database-reference-sql-functions-lists-list-sort): sorts, smallest first | `[1, 3, 3, 10, NULL]` |

```
run("SELECT list_reverse(l), list_reverse_sort(l), list_sort(l, 'DESC'), list_sort(l) "
    "FROM (SELECT [3, 1, NULL, 3, 10] AS l)")
```

```
[([10, 3, None, 1, 3], [10, 3, 3, 1, None], [10, 3, 3, 1, None], [1, 3, 3, 10, None])]
```

Clean up:

```
run(f"DROP TABLE IF EXISTS {TABLE}")
run(f"DROP SCHEMA IF EXISTS {SCHEMA}")
conn.close()
```

```
[]
[]
```

## See also

- [list_reverse_sort](/develop/docs/dev-database-reference-sql-functions-lists-list-reverse-sort): sort a list in descending order.
- [reverse](/develop/docs/dev-database-reference-sql-functions-string-reverse): reverse a string.
- [List, struct and map functions](/develop/docs/dev-database-reference-sql-functions-lists-and-structs): all the list functions.
- [Where filters run](/develop/docs/dev-database-reference-sql-select#where-filters-run) and [pushdowns](/develop/docs/dev-database-reference-pushdowns).
- [EXPLAIN](/develop/docs/dev-database-reference-sql-explain): how to read a plan.