Re: For cursors, there is FETCH and MOVE, why no TELL? - Mailing list pgsql-hackers

From Marc Balmer
Subject Re: For cursors, there is FETCH and MOVE, why no TELL?
Date
Msg-id 54D884EA.1060808@msys.ch
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In response to Re: For cursors, there is FETCH and MOVE, why no TELL?  (Pavel Stehule <pavel.stehule@gmail.com>)
Responses Re: For cursors, there is FETCH and MOVE, why no TELL?  (Pavel Stehule <pavel.stehule@gmail.com>)
Re: For cursors, there is FETCH and MOVE, why no TELL?  (Pavel Stehule <pavel.stehule@gmail.com>)
List pgsql-hackers
> 
> 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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