Thanks, Tom.
Wouldn't this mean that cursors are noticeably non-optimal even for normal data sizes, since the entire data to be streamed from the table is always duplicated into another buffer and then streamed?
Wouldn't this mean that cursors are noticeably non-optimal even for normal data sizes, since the entire data to be streamed from the table is always duplicated into another buffer and then streamed?
> if you want the whole query result at once, why are you bothering with a cursor?
The PostgreSQL docs (https://www.postgresql.org/docs/9.6/static/plpgsql-cursors.html#AEN66551) clearly recommend cursors as a way to return a reference to a large result set from a function (as I understood, this is recommended precisely as a way to avoid tuple-based buffering of the data).
So following that advice, it's not unreasonable that I would actually have a cursor to a large dataset.
Then, I would ideally want to be able to fetch the data from that cursor without the entire data getting duplicated (even if only a bit at a time instead of all at once, which seems to be the best case behaviour) as I go.
Additionally, I thought that if I had a streaming use-case (which I do), and a streaming data-access layer (which I do), then since `SELECT * FROM large` is absolutely fine, end-to-end, in that situation, then by symmetry and the principle of least astonishment `FETCH ALL FROM cursor` might be fine too.
