is pq memory friendly?

[nuliknol]

I need to query retrieve 10 million records with lib/pq.
Is rows.Next() memory friendly or do I have to use cursors?

[timbunce]

Cursors, sadly. See #635 and #81 (now 5 years old).

[johto]

@timbunce You have that backwards. Those issues happen because pq uses a cursor underneath. If we read all the rows into memory first, we wouldn't have those issues.

In other words, there's no need to use a cursor explicitly.

[johto]

In other words, there's no need to use a cursor explicitly.

I guess I should clarify: there's no need to use a cursor explicitly if you're only worried about memory usage.

[timbunce]

Yes, you're right, I'd got it backwards. Thanks @johto!

[mbeirouti]

@johto are you saying pq uses a server side or client side cursor? I can't seem to find any reference in the code base to a server side cursor except in unused error messages and types, maybe I'm missing something..

[cbandy]

@mbeirouti it's implicit in the wire protocol. The unnamed portal acts like a server side cursor.

https://www.postgresql.org/docs/current/protocol-flow.html

[auror]

@mbeirouti Just to clarify,

1. Does this unnamed portal act as an explicit server side cursor i.e., DECLARE Cursor?
2. What are the significant differences b/w these two approaches?