On Fri, 2022-10-14 at 13:52 +0200, Dominique Devienne wrote: > On Wed, Oct 5, 2022 at 8:17 PM Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > > Laurenz Albe <laurenz.albe@xxxxxxxxxxx> writes: > > > On Wed, 2022-10-05 at 16:38 +0200, Dominique Devienne wrote: > > > Yes, you have to use PQcmdTuples(), and you have to convert the string to an integer. > > > But don't worry: the result will *not* be "INSERT 0 5", it will be just "5" > > Thanks. What's the leading 0 though, then? > I guessed it might be the number of rows returned, but it isn't, see below: > > postgres=# create table foo (id serial primary key, v int); > CREATE TABLE > postgres=# insert into foo (v) values (1), (2) returning id; > id > ---- > 1 > 2 > (2 rows) > > INSERT 0 2 That 0 is the OID of the newly inserted tuple. Since there are no more tables WITH OIDS, the number is always 0, but is left in the output for compatibility reasons. > > Yeah, just applying atoi() or atol() to the result should be enough. > > Thanks too. Since I'm in C++, I used <charconv> instead, and > discovered it can be empty something, not 0. > I guess atoi() would have hidden that distinction, and worked anyway > (returning 0). > > In the same topic, I've noticed an INSERT returns PGRES_COMMAND_OK, > while an INSERT-RETURNING returns PGRES_TUPLES_OK. So there's no way > to use the status to distinguish a SELECT from anything else? A RETURNING clause > makes any statement supporting it an hybrid of a command and a query, > but then how > does one know the exact "kind" of the statement? > > E.g. So how does psql show INSERT in either cases? By parsing the SQL > itself, client-side? > Or is there a libpq API on PGresult that would allow to get the type > of statement the result is from? The command tag is not what you look at. You simply check the result from an INSERT statement. If it is PGRES_TUPLES_OK, it must have been INSERT ... RETRUNING. Yours, Laurenz Albe -- Cybertec | https://www.cybertec-postgresql.com
