But wait,if they already have functions why do they need edge functions?

Supabase Functions: Your PostgreSQL Toolbox

Supabase functions, also known as database functions, are essentially PostgreSQL stored procedures. They are executable blocks of SQL code that can be called from within SQL queries.

Edge Functions: Beyond the Database

In contrast, Edge functions are server-side TypeScript functions that run on the Deno runtime. They are similar to Firebase Cloud Functions but offer a more flexible and open-source alternative.

Supabase: A PostgreSQL Platform

Beyond its role as an open-source alternative to Firebase, Supabase has evolved into a comprehensive PostgreSQL platform. It provides first-class support for PostgreSQL functions, integrating them seamlessly into its built-in utilities and allowing you to create and manage custom functions directly from the Supabase dashboard.

Structure of a basic postgres functon

Breakdown:

1. CREATE FUNCTION: This keyword indicates that we're defining a new function.
2. my_function(): This is the name of the function. You can choose any meaningful name you prefer.
3. RETURNS int: This specifies the return type of the function. In this case, the function will return an integer value.
4. AS $$: This begins the function body, enclosed within double dollar signs ($$) to delimit it.
5. BEGIN: This marks the start of the function's executable code.
6. RETURN 42;: This statement specifies the value that the function will return. In this case, it's the integer 42.
7. END;: This marks the end of the function's executable code.
8. $$ LANGUAGE sql;: This specifies the language in which the function is written. In this case, it's SQL.

Purpose:

This function defines a simple SQL function named my_function that returns the integer value 42. It's a basic example to demonstrate the structure and syntax of a function definition in PostgreSQL.

Key points to remember:

• You can replace my_function with any desired function name.
• The return type can be any valid data type, such as text, boolean, date, or a user-defined type.
• The function body can contain complex logic, including conditional statements, loops, and calls to other functions.
• The $$ delimiters are used to enclose the function body in a language-independent manner.
• Postgres functions can also be called by postgres TRIGGERS which are like functions but react to specific events like insert, update or delete on a table
• to execute this function

• to list this function

• to drop this function

Supabase postgres functions

Built-in functions

Supabase makes use of postgres functions to perform certain tasks within your database.

short list of exampales includes

Supabase functions view on the dashboard To view some of these functions in Supabase, you can check under database > functions

Useful Supabase PostgreSQL Functions

Creating a user_profile Table on User Signup

Supabase stores user data in the auth.users table, which is private and should not be accessed or modified directly. A recommended approach is to create a public users or user_profiles table and link it to the auth.users table.

While this can be done using client-side SDKs by chaining a create user request with a successful signup request, it's more reliable and efficient to handle it on the Supabase side. This can be achieved using a combination of a TRIGGER and a FUNCTION.

• Add custom claims on jwt creation (RBAC) supabse has a detailed article and video on this .

we need 2 tabbles

• public.roles and public.role_permissions

example of user role

| id | user_id | role |
| --- | --- | --- |
| 1 | user-1 | admin |
| 2 | user-2 | moderator |

example of a role permission table

| id | role | permission |
| --- | --- | --- |
| 1 | admin | channels.update |
| 2 | admin | messages.update |
| 3 | admin | messages.delete |
| 4 | admin | messages.delete |
| 5 | moderator | channels.update |
| 6 | moderator | messages.update |

user with user_id = user-1 will have admin and moderator roles and can delete channels and messages

users with user_id = user-2 can only update channels and messages with the moderator role

then create a function that will be called to authorize on RLS policies

Improved Text:

Creating RPC Endpoints

Supabase functions can be invoked using the rpc function. This is especially useful for writing custom SQL queries when the built-in PostgreSQL APIs are insufficient, such as calculating vector cosine similarity using pg_vector.

```sql
create or replace function match_documents (
query_embedding vector(384),
match_threshold float,
match_count int
)
returns table (
id bigint,
title text,
body text,
similarity float
)
language sql stable
as $$
select
documents.id,
documents.title,
documents.body,
1 - (documents.embedding <=> query_embedding) as similarity
from documents
where 1 - (documents.embedding <=> query_embedding) > match_threshold
order by (documents.embedding <=> query_embedding) asc
limit match_count;
$$;

ts const { data: documents } = await supabaseClient.rpc('match_documents', { query_embedding: embedding, // Pass the embedding you want to compare match_threshold: 0.78, // Choose an appropriate threshold for your data match_count: 10, // Choose the number of matches })

sql -- check if user with roles authenticated or anon submitted an updatedat column and replace it with the current time , if not (thta is an admin) allow it CREATE or REPLACE function public.omit_updated__at () returns trigger as $$ BEGIN IF auth.role() IS NOT NULL AND auth.role() IN ('anon', 'authenticated') THEN NEW.updated_at = now(); END IF; RETURN NEW; END; $$ language plpgsql;
```

Summary

With a little experimentation, you can unlock the power of Supabase functions and their AI-powered SQL editor. This lowers the barrier to entry for the niche knowledge required to get this working.

Why choose Supabase functions?

• Extend Supabase's API: Supabase can only expose so much through its API. Postgres, however, is a powerful database. Any action you can perform with SQL statements can be wrapped in a function and called from the client or by a trigger.
• Reduce the need for dedicated backends: Supabase functions can fill the simple gaps left by the client SDKs, allowing you to focus on shipping.
• Avoid vendor lock-in: Supabase functions are just Postgres. If you ever need to move to another hosting provider, these functionalities will continue to work.