Query events with Pool

[jtuu]

With a client we can use the "row" event of a query.
client.query("select id from table").on("row", row => console.log(row))

{ id: 1 }
{ id: 2 }
{ id: 3 }
{ id: 4 }
{ id: 5 }

But with a pool we can't do this.
pool.query("select id from table").on("row", row => console.log(row))
TypeError: pool.query(...).on is not a function

Is it possible to use the query events with pool?

[lebreRafael]

I'm facing the same problem here. I don't want to refactor all code using loops instead of .on('row') to change pg.client to pg.pool

[RenanBardy]

I have the same error in my application. Is there any way to fix this?

[brianc]

The pool supports returning a client if you want to do something like that:

pool.connect(function(err, client, done) {
  var query = client.query('whatever')
  query.on('row', //etc)
  //...etc
})

That API ^^ has existed for years and is still there. 😄

pool.query is a helper method for the most common operation which is "I want to run a query and get the rows back." If you want to do something "fancier" with a client (transactions, row events, listen/notify, pg-query-stream, etc) then pool.query isn't for you. I don't really want to extend the pool.query method with even more functionality...

Curious: why are you using query.on('row') in the first place?

[lebreRafael]

@brianc I'm using query.on('row') because I need to do something for each line returned and with the row event I don't need to write loops in my code.

[jtuu]

@brianc Thank you for the example, it helped me. I get that pool.query is supposed to be a helper method but perhaps it should use a different name to avoid confusion/inconsistency between client.query and pool.query. Btw I use query.on('row') to "stream" data through websocket in realtime.

[charmander]

Discouraged for Client.prototype.query as well in pg 7.

[jcuenod]

I know this is an old thread but I'm wanted to do something like what @jtuu is describing.

I want to use pool so I don't have to manage a warm pool of db connections (which is what I understand the point of pool to be). I want to stream results to clients though and the row event seems like a much better option that polling the cursor.

What is the best way of accomplishing this?

[charmander]

I want to stream results to clients though and the row event seems like a much better option that polling the cursor.

@jcuenod That’s not what the row event did, but it’s an easy mistake to make (and why it’s not part of the public API now). You will probably want to use a cursor, but it doesn’t have to be directly.

[bluenote10]

If you want to do something "fancier" with a client (transactions, row events, listen/notify, pg-query-stream, etc) then pool.query isn't for you. I don't really want to extend the pool.query method with even more functionality...

@brianc Thanks for the clarification, that really makes sense. A quick question about the exact semantics: When using client.on('notification', callback) on a client acquired from a pool, is it safe to release this client back to the pool and still get notify updates, or does this require holding on to the client indefinitely?