Looking for a quick way to increment a value in a supabase table?

Supabase functions

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The supabase sdk allows you to do a range of things with the table however it doesn't let you execute custom sql. However, it does let you trigger postgres function with the rpc method https://supabase.com/docs/reference/javascript/rpc

We can combine this with postgres function that can update a table field of choice to easily increment values

Example

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You have a table metric like this:

| id | user_id | count_a | count_b | | --- | ------- | ------- | ------- | | 1 | 1 | 0 | 0 | | 2 | 2 | 0 | 0 |

and you want to simply increment a column from a backend call

We can define a postgres function which takes a user_id and the field/column you want to increment

CREATE OR REPLACE FUNCTION increment(user_id_to_inc INT, field_name TEXT)
RETURNS VOID AS
$func$
BEGIN
    EXECUTE format('INSERT INTO metric (user_id, %I)
    VALUES ($1, 1) ON CONFLICT (user_id) DO UPDATE
    SET %I = metric.%I + 1 WHERE metric.user_id = $1', field_name, field_name, field_name, field_name)
    USING user_id_to_inc;
END
$func$ LANGUAGE plpgsql;

Note: There needs to be unique constraint on user_id and any field name that you want to increment must have a default of 0

Supabase SQL editor

We need to add the postgres function into the supabase dashboard

Go to the sql editor on supabase

Create a new query, copy in the function and run query

We can now call this function from our application

Here is an example of invoking the postgres from typescript using the supabase sdk

export async function incrementCountForUser(
  userID: number,
  count_field: string
) {
  const field_to_increment = `count_${count_field}`; // count_a or count_b
  const { data, error } = await supabaseBrowser.rpc("increment", {
    user_id_to_inc: userID,
    field_name: field_to_increment,
  });
  if (error) {
    console.log(error);
  }
}