Re: For cursors, there is FETCH and MOVE, why no TELL?

Hi

the patch can be very simple:

diff --git a/src/backend/commands/portalcmds.c
b/src/backend/commands/portalcmds.c
new file mode 100644
index 2794537..20b9206
*** a/src/backend/commands/portalcmds.c
--- b/src/backend/commands/portalcmds.c
*************** PerformPortalFetch(FetchStmt *stmt,
*** 181,189 ****

/* Return command status if wanted */
if (completionTag)
! snprintf(completionTag, COMPLETION_TAG_BUFSIZE, "%s %ld",
stmt->ismove ? "MOVE" : "FETCH",
! nprocessed);
}

/*
--- 181,190 ----

/* Return command status if wanted */
if (completionTag)
! snprintf(completionTag, COMPLETION_TAG_BUFSIZE, "%s %ld
%ld",
stmt->ismove ? "MOVE" : "FETCH",
! nprocessed,
! portal->portalPos);
}

/*

2015-02-09 10:59 GMT+01:00 Marc Balmer <marc(at)msys(dot)ch>:

> >
> > 2015-02-09 10:37 GMT+01:00 Marc Balmer <marc(at)msys(dot)ch <mailto:
> marc(at)msys(dot)ch>>:
> >
> > Currently there are FETCH and the (non standard) MOVE commands to
> work
> > on cursors.
> >
> > (I use cursors to display large datasets in a page-wise way, where
> the
> > user can move per-page, or, when displaying a single record, per
> record.
> > When the user goes back from per-record view to page-view, I have to
> > restore the cursor to the position it was on before the user changed
> to
> > per-record view.)
> >
> > I have to "manually" keep track of the cursor position, but in some
> > cases it would definitely be easier to just query the current cursor
> > position directly from the database and later use "MOVE ABSOLUTE" to
> > rewind it to that position. That could be achieved e.g. by a
> > hypothetical "TELL <cursor-name>" command. It does, however, not
> exist
> > and I have not found an alternative. Is there a way to query the
> > current cusros position at all? If not, does a TELL command sound
> like
> > a good or bad idea?
> >
> >
> > It sounds like good idea.
> >
> > Do we need a new statement? We can implement returning the position to
> > MOVE statement. It returns a delta, but it can returns a absolute
> > position too.
>
> On second thought, a new statement is not needed at all. As Heikki
> noticed in hsi reply, it could either be a new function or have move to
> return the current position somehow(tm). Or a nw option to move, maybe
> "MOVE NOT" (don't move the cursor but return it's position?
>
>
> --
> Sent via pgsql-hackers mailing list (pgsql-hackers(at)postgresql(dot)org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-hackers
>