Supabase•4w ago

Error trying to connect to postgres_changes in realtime

Hello I'm facing a problem here related to realtime database. I have a table called documents, I enabled RLS for everyone can select and also enabled realtime, but i try to connect to it many times in my code and it doesn't work, the status keep saying: CLOSED, CHANNEL_ERROR I tried changing to "broadcast" and it subscribed, only in postgres_changes it fails.

16 Replies

garyaustin•4w ago

So you close the channel in the useEffect? If so and you use the same channel name for two different pages as one is closing the other is opening and they step on each other. At least that is one situation I've seen for the Closing of the channel with useEffect involved.

SudsierSpace👍OP•4w ago

no let me show it all to be better for u

useEffect(() => {
        read().then(data => {
            if (data) setDocuments(data);
        })
        const channel = supabase.channel('documents')
        channel.on(
            "postgres_changes",
            { event: "*", schema: "public", table: "documents" },
            (payload) => {
                console.log("INSERT received:", payload);
            }
        )
        .subscribe((status) => {
            console.log("Status:", status);
        });
       
        setTimeout(() => {
            channel.send({
                type: "broadcast",
                event: "ping",
                payload: { msg: "Hello from client" },
            });
        }, 2000);
    }, [])

useEffect(() => {
        read().then(data => {
            if (data) setDocuments(data);
        })
        const channel = supabase.channel('documents')
        channel.on(
            "postgres_changes",
            { event: "*", schema: "public", table: "documents" },
            (payload) => {
                console.log("INSERT received:", payload);
            }
        )
        .subscribe((status) => {
            console.log("Status:", status);
        });
       
        setTimeout(() => {
            channel.send({
                type: "broadcast",
                event: "ping",
                payload: { msg: "Hello from client" },
            });
        }, 2000);
    }, [])

hm... so its better to use it outside?

garyaustin•4w ago

What is the purpose of the broadcast?

SudsierSpace👍OP•4w ago

the broadcast is when i create a doc i can listen to this event

garyaustin•4w ago

No. Broadcast is not the same as Postgres changes.

SudsierSpace👍OP•4w ago

oh sorry so let me change it at first i connected with .on("broadbast") that was alright no error

garyaustin•4w ago

There are two ways to do this. One is postgres_changes. You set those up on the tables with publications (a tab in the dashboard) an have to meet RLS.

SudsierSpace👍OP•4w ago

then i changed to .on("postgres_changes") and thats how it's now with error

garyaustin•4w ago

The other method that can be used is database broadcast where you use a private broadcast channel and a trigger function on the table to send table information.

SudsierSpace👍OP•4w ago

understand not much actually the trigger function do you have a suggestion for helping me like in the code etc let me search about this trigger you said there

garyaustin•4w ago

You have to pick a method. Postgres_changes is "easier". It is documented in the realtime docs as that. It requires realtime enabled on the table and that you meet RLS. It is slower than the next method. https://supabase.com/docs/guides/realtime/postgres-changes The other is is Broadcast with a trigger https://supabase.com/docs/guides/realtime/subscribing-to-database-changes#using-broadcast

SudsierSpace👍OP•4w ago

yes now i understand well So I should try this one and forget the postgres_changes bc of the error

garyaustin•4w ago

If I were doing a new app I would learn the Broadcast messages with the database trigger method as it is faster and more flexible. But it is a bit harder to learn and get going.

SudsierSpace👍OP•4w ago

yeah but anyways thanks a lot

garyaustin•4w ago

I don't know why your postgres_changes above was closing, but you can't do broadcast on that same channel.

SudsierSpace👍OP•4w ago

ook thank you

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Error trying to connect to postgres_changes in realtime

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