Re: For cursors, there is FETCH and MOVE, why no TELL? - Mailing list pgsql-hackers
| From | Pavel Stehule |
|---|---|
| Subject | Re: For cursors, there is FETCH and MOVE, why no TELL? |
| Date | |
| Msg-id | CAFj8pRDsuTgf-FHvh0Q5ABy=aQtPMxFnG-__y+0BoewEwFuBsw@mail.gmail.com Whole thread Raw |
| In response to | Re: For cursors, there is FETCH and MOVE, why no TELL? (Marc Balmer <marc@msys.ch>) |
| Responses |
Re: For cursors, there is FETCH and MOVE, why no TELL?
|
| List | pgsql-hackers |
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);
}
/*
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@msys.ch>:
>
> 2015-02-09 10:37 GMT+01:00 Marc Balmer <marc@msys.ch <mailto:marc@msys.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?
--
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