---
id: 'functions'
title: 'Database Functions'
description: 'Creating and using Postgres functions.'
video: 'https://www.youtube.com/v/MJZCCpCYEqk'
---

Postgres has built-in support for [SQL functions](https://www.postgresql.org/docs/current/sql-createfunction.html).
These functions live inside your database, and you can call them from your app with [`rpc()`](../../reference/javascript/rpc).

## Quick demo

<YouTube id="MJZCCpCYEqk" title="Creating and calling Postgres functions" />

## Getting started

Create a database function from the Dashboard, or write the SQL yourself against a
[direct connection](../../guides/database/connecting-to-postgres).

To use the Dashboard:

1. Go to the **SQL Editor** section.
2. Click **New Query**.
3. Enter the SQL that creates or replaces your database function.
4. Click **Run**. You can also press `cmd+enter` or `ctrl+enter`.

## Basic functions [#simple-functions]

Create a basic database function that returns the string "hello world".

```sql
create or replace function hello_world() -- 1
returns text -- 2
language sql -- 3
as $$  -- 4
  select 'hello world';  -- 5
$$; --6

```

<details>
<summary>Show/Hide Details</summary>

At its most basic, a function has the following parts:

1. `create or replace function hello_world()`: The function declaration, where `hello_world` is the name of the function. Use `create` for a new function, `replace` for one that exists, or `create or replace` when the function might not exist yet.
2. `returns text`: The type of data the function returns. For a function that returns nothing, write `returns void`.
3. `language sql`: The language used inside the function body. This can also be a procedural language: `plpgsql`, `plpython`, etc.
4. `as $$`: The function wrapper. Anything inside the `$$` symbols is part of the function body.
5. `select 'hello world';`: A basic function body. The function returns the result of the last `select` statement in its body.
6. `$$;`: The closing symbols of the function wrapper.

</details>

<Admonition type="caution">

Overloaded functions aren't supported. Give every function a unique name.

</Admonition>

After you create the function, you can run it inside the database with SQL, or with one of the client libraries.

<Tabs
  scrollable
  size="small"
  type="underlined"
  defaultActiveId="sql"
  queryGroup="language"
>
<TabPanel id="sql" label="SQL">

```sql
select hello_world();
```

</TabPanel>
<TabPanel id="js" label="JavaScript">

```js
const { data, error } = await supabase.rpc('hello_world')
```

Reference: [`rpc()`](../../reference/javascript/rpc)

</TabPanel>
<$Show if="sdk:dart">
<TabPanel id="dart" label="Dart">

```dart
final data = await supabase
  .rpc('hello_world');
```

Reference: [`rpc()`](../../reference/dart/rpc)

</TabPanel>
</$Show>
<$Show if="sdk:swift">
<TabPanel id="swift" label="Swift">

```swift
try await supabase.rpc("hello_world").execute()
```

Reference: [`rpc()`](../../reference/swift/rpc)

</TabPanel>
</$Show>
<$Show if="sdk:kotlin">
<TabPanel id="kotlin" label="Kotlin">

```kotlin
val data = supabase.postgrest.rpc("hello_world")
```

Reference: [`rpc()`](../../reference/kotlin/rpc)

</TabPanel>
</$Show>
<$Show if="sdk:python">
<TabPanel id="python" label="Python">

```python
data = supabase.rpc('hello_world').execute()
```

Reference: [`rpc()`](../../reference/python/rpc)

</TabPanel>
</$Show>
<$Show if="sdk:csharp">
<TabPanel id="csharp" label="C#">

```c#
await supabase.Rpc("hello_world", null);
```

Reference: [`Rpc()`](../../reference/csharp/rpc)

</TabPanel>
</$Show>
</Tabs>

## Returning data sets

A database function can also return a data set from a [table](../../guides/database/tables) or a view.

For example, take a database holding some Star Wars data:

<Tabs
  scrollable
  size="small"
  type="underlined"
  defaultActiveId="data"
  queryGroup="example-view"
>
<TabPanel id="data" label="Data">

### Planets

```
| id  | name     |
| --- | -------- |
| 1   | Tatooine |
| 2   | Alderaan |
| 3   | Kashyyyk |
```

### People

```
| id  | name             | planet_id |
| --- | ---------------- | --------- |
| 1   | Anakin Skywalker | 1         |
| 2   | Luke Skywalker   | 1         |
| 3   | Princess Leia    | 2         |
| 4   | Chewbacca        | 3         |
```

</TabPanel>
<TabPanel id="sql" label="SQL">

```sql
create table planets (
  id serial primary key,
  name text
);

insert into planets
  (id, name)
values
  (1, 'Tattoine'),
  (2, 'Alderaan'),
  (3, 'Kashyyyk');

create table people (
  id serial primary key,
  name text,
  planet_id bigint references planets
);

insert into people
  (id, name, planet_id)
values
  (1, 'Anakin Skywalker', 1),
  (2, 'Luke Skywalker', 1),
  (3, 'Princess Leia', 2),
  (4, 'Chewbacca', 3);
```

</TabPanel>
</Tabs>

The following function returns all the planets:

```sql
create or replace function get_planets()
returns setof planets
language sql
as $$
  select * from planets;
$$;
```

Because this function returns a table set, you can apply filters and selectors to it. To get the first planet only:

<Tabs
  scrollable
  size="small"
  type="underlined"
  defaultActiveId="sql"
  queryGroup="language"
>
<TabPanel id="sql" label="SQL">

```sql
select *
from get_planets()
where id = 1;
```

</TabPanel>
<TabPanel id="js" label="JavaScript">

```js
const { data, error } = supabase.rpc('get_planets').eq('id', 1)
```

</TabPanel>
<$Show if="sdk:dart">
<TabPanel id="dart" label="Dart">

```dart
final data = await supabase
  .rpc('get_planets')
  .eq('id', 1);
```

</TabPanel>
</$Show>
<$Show if="sdk:swift">
<TabPanel id="swift" label="Swift">

```swift
let response = try await supabase.rpc("get_planets").eq("id", value: 1).execute()
```

</TabPanel>
</$Show>
<$Show if="sdk:kotlin">
<TabPanel id="kotlin" label="Kotlin">

```kotlin
val data = supabase.postgrest.rpc("get_planets") {
    filter {
        eq("id", 1)
    }
}
```

</TabPanel>
</$Show>
<$Show if="sdk:python">
<TabPanel id="python" label="Python">

```python
data = supabase.rpc('get_planets').eq('id', 1).execute()
```

</TabPanel>
</$Show>
</Tabs>

## Passing parameters

Create a function that inserts a new planet into the `planets` table and returns the new ID. This function uses the `plpgsql` language.

```sql
create or replace function add_planet(name text)
returns bigint
language plpgsql
as $$
declare
  new_row bigint;
begin
  insert into planets(name)
  values (add_planet.name)
  returning id into new_row;

  return new_row;
end;
$$;
```

You can run this function inside your database with a `select` query, or with the client libraries:

<Tabs
  scrollable
  size="small"
  type="underlined"
  defaultActiveId="sql"
  queryGroup="language"
>
<TabPanel id="sql" label="SQL">

```sql
select * from add_planet('Jakku');
```

</TabPanel>
<TabPanel id="js" label="JavaScript">

```js
const { data, error } = await supabase.rpc('add_planet', { name: 'Jakku' })
```

</TabPanel>
<$Show if="sdk:dart">
<TabPanel id="dart" label="Dart">

```dart
final data = await supabase
  .rpc('add_planet', params: { 'name': 'Jakku' });
```

</TabPanel>
</$Show>
<$Show if="sdk:swift">
<TabPanel id="swift" label="Swift">

Using `Encodable` type:

```swift
struct Planet: Encodable {
  let name: String
}

try await supabase.rpc(
  "add_planet",
  params: Planet(name: "Jakku")
)
.execute()
```

Using `AnyJSON` convenience` type:

```swift
try await supabase.rpc(
  "add_planet",
  params: ["name": AnyJSON.string("Jakku")]
)
.execute()
```

</TabPanel>
</$Show>
<$Show if="sdk:kotlin">
<TabPanel id="kotlin" label="Kotlin">

```kotlin
val data = supabase.postgrest.rpc(
    function = "add_planet",
    parameters = buildJsonObject { //You can put here any serializable object including your own classes
        put("name", "Jakku")
    }
)
```

</TabPanel>
</$Show>
<$Show if="sdk:python">
<TabPanel id="python" label="Python">

```python
data = supabase.rpc('add_planet', params={'name': 'Jakku'}).execute()
```

</TabPanel>
</$Show>
<$Show if="sdk:csharp">
<TabPanel id="csharp" label="C#">

```c#
await supabase.Rpc("add_planet", new Dictionary<string, object> { { "name", "Jakku" } });
```

</TabPanel>
</$Show>
</Tabs>

## Suggestions

### Database Functions vs Edge Functions

For data-intensive operations, use database functions. They run inside your database, and you can call them remotely with the [REST and GraphQL API](../api).

For use cases that need low latency, use [Edge Functions](../../guides/functions). They're globally distributed and you write them in TypeScript.

### Security `definer` vs `invoker`

Postgres runs a function either as the user _calling_ it (`invoker`) or as its _creator_ (`definer`). For example:

```sql
create function hello_world()
returns text
language plpgsql
security definer set search_path = ''
as $$
begin
  return 'hello world';
end;
$$;
```

Prefer `security invoker`, which is also the default. When you use `security definer`, you must set the `search_path`.

With an empty search path, `search_path = ''`, name the schema for every relation in the function body, such as `from public.table`. An empty search path limits the damage when the function can reach a schema you don't want the calling user to reach.

### Function privileges

By default, any role can run a database function. You can restrict execution in two ways:

1.  Revoke on a case-by-case basis. Revoke execute for the functions you want to protect, from both `public` and the role you're restricting:

    ```sql
    revoke execute on function public.hello_world from public;
    revoke execute on function public.hello_world from anon;
    ```

1.  Restrict execution by default, then grant access to the roles that need each function.

    To restrict every function that exists, revoke execute from both `public` and the role you want to restrict:

    ```sql
    revoke execute on all functions in schema public from public;
    revoke execute on all functions in schema public from anon, authenticated;
    ```

    To restrict every function created later, change the default privileges for both `public` and the role you want to restrict:

    ```sql
    alter default privileges in schema public revoke execute on functions from public;
    alter default privileges in schema public revoke execute on functions from anon, authenticated;
    ```

    You can then regrant permissions for a specific function to a specific role:

    ```sql
    grant execute on function public.hello_world to authenticated;
    ```

### Debugging functions

Add logs to help you debug a function. Logs matter most in a complex function.

Good targets to log include:

- Values of (non-sensitive) variables
- Returned results from queries

#### General logging

Use the `raise` keyword to write custom logs to the [Postgres logs](/dashboard/project/_/logs/postgres-logs) in the Dashboard. Three severity levels appear by default:

- `log`
- `warning`
- `exception` (error level)

```sql
create function logging_example(
  log_message text,
  warning_message text,
  error_message text
)
returns void
language plpgsql
as $$
begin
  raise log 'logging message: %', log_message;
  raise warning 'logging warning: %', warning_message;

  -- immediately ends function and reverts transaction
  raise exception 'logging error: %', error_message;
end;
$$;

select logging_example('LOGGED MESSAGE', 'WARNING MESSAGE', 'ERROR MESSAGE');
```

#### Error handling

You can create custom errors with the `raise exception` keywords.

A common pattern is to throw an error when a variable doesn't meet a condition:

```sql
create or replace function error_if_null(some_val text)
returns text
language plpgsql
as $$
begin
  -- error if some_val is null
  if some_val is null then
    raise exception 'some_val should not be NULL';
  end if;
  -- return some_val if it is not null
  return some_val;
end;
$$;

select error_if_null(null);
```

Value checking is common, so Postgres provides the `assert` keyword as a shorthand. It takes the following format:

```sql
-- throw error when condition is false
assert <some condition>, 'message';
```

For example:

```sql
create function assert_example(name text)
returns uuid
language plpgsql
as $$
declare
  student_id uuid;
begin
  -- save a user's id into the user_id variable
  select
    id into student_id
  from attendance_table
  where student = name;

  -- throw an error if the student_id is null
  assert student_id is not null, 'assert_example() ERROR: student not found';

  -- otherwise, return the user's id
  return student_id;
end;
$$;

select assert_example('Harry Potter');
```

You can also capture and modify an error message with the `exception` keyword:

```sql
create function error_example()
returns void
language plpgsql
as $$
begin
  -- fails: cannot read from nonexistent table
  select * from table_that_does_not_exist;

  exception
      when others then
          raise exception 'An error occurred in function <function name>: %', sqlerrm;
end;
$$;
```

#### Advanced logging

For a more complex function, or for harder debugging, log the following:

- Formatted variables
- Individual rows
- Start and end of function calls

```sql
create or replace function advanced_example(num int default 10)
returns text
language plpgsql
as $$
declare
    var1 int := 20;
    var2 text;
begin
    -- Logging start of function
    raise log 'logging start of function call: (%)', (select now());

    -- Logging a variable from a SELECT query
    select
      col_1 into var1
    from some_table
    limit 1;
    raise log 'logging a variable (%)', var1;

    -- It is also possible to avoid using variables, by returning the values of your query to the log
    raise log 'logging a query with a single return value(%)', (select col_1 from some_table limit 1);

    -- If necessary, you can even log an entire row as JSON
    raise log 'logging an entire row as JSON (%)', (select to_jsonb(some_table.*) from some_table limit 1);

    -- When using INSERT or UPDATE, the new value(s) can be returned
    -- into a variable.
    -- When using DELETE, the deleted value(s) can be returned.
    -- All three operations use "RETURNING value(s) INTO variable(s)" syntax
    insert into some_table (col_2)
    values ('new val')
    returning col_2 into var2;

    raise log 'logging a value from an INSERT (%)', var2;

    return var1 || ',' || var2;
exception
    -- Handle exceptions here if needed
    when others then
        raise exception 'An error occurred in function <advanced_example>: %', sqlerrm;
end;
$$;

select advanced_example();
```

## Resources

- Official Client libraries: [JavaScript](../../reference/javascript/rpc) and [Flutter](../../reference/dart/rpc)
- Community client libraries: [github.com/supabase-community](https://github.com/supabase-community)
- Postgres Official Docs: [Chapter 9. Functions and Operators](https://www.postgresql.org/docs/current/functions.html)
- Postgres Reference: [CREATE FUNCTION](https://www.postgresql.org/docs/9.1/sql-createfunction.html)

## Deep dive

### Create Database Functions

<YouTube id="MJZCCpCYEqk" title="Creating a Postgres function in the dashboard" />

### Call Database Functions using JavaScript

<YouTube id="I6nnp9AINJk" title="Calling a Postgres function from JavaScript" />

### Using Database Functions to call an external API

<YouTube id="rARgrELRCwY" title="Calling an external API from a Postgres function" />