Christophe Pettus a écrit :
On Feb 4, 2021, at 09:21, Denis Laxalde <denis.laxa...@dalibo.com> wrote:
Well, maybe I'm missing something... In the examples above, (written
down explicitly to understand where IO happens), if I shut down postgres
between 'await conn.execute()' and 'await cur.fetchall()', the first
example breaks but the second doesn't. Perhaps the autocommit mention
was misleading; it's enough to insert 'await conn.commit()' before
'await cur.fetchall()' to reproduce. So (and again, unless I'm missing
something), if this is not "by design", maybe this is bug?
You're relying on private knowledge, not an API guarantee, as to "where I/O
happens" here. Like any expectation based on private knowledge, you can get tripped
up by that.
Well, that's just an exercise for me to understand where things happen.
Of course, I'd expect an 'await' expression to possibly involve I/O in
real life.
If it comes down to "cursor isn't a good name for this class," that's probably
true, but we're a decade past making that decision.
That, and the fact that fetch*() methods do not fetch actually. (For the
synchronous case, I'm quite convinced now this is too late to change.)
As far as the async interface is concerned, I think there is no adoption
issue because there's no precedent use from psycopg2. So we could
expose two API: cursorless querying ('await conn.execute()') and have a
single server-side cursor class.
Right now, switching from using just a client-side cursor object to server-side
cursor preserves largely preserves the API. I think that's a valuable feature
that's worth retaining.
Worth retaining, maybe. Is it worth imposing the 'await cursor.fetch*()'
pattern to everybody when it does not appear needed? I'm not so sure, as
this would be at the cost of readability and clarity. (On the other
hand, if I were to migrate some code to use server-side cursors, I would
probably do it on a case-by-case basis; so if the cursor wasn't there in
the first place, adding it would be little trouble in contrast to
deciding where a server-side cursor is needed or not.)
