Re: MOVE strangeness

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Sorry, I am not understanding. If he does:
> > ...
> > here, isn't he sitting at the start of the fourth row, no?
>
> No. He is sitting *on* the third row. If he now does FETCH 1, he will
> advance to and return the fourth row; on the other hand, if he does
> FETCH -1, he will back up to and return the second row.

OK, and it makes sense FETCH -1 will move back a row rather than
re-reading the row.

> The cursor must be considered to be positioned on its current row, not
> between rows, or the SQL-defined operations UPDATE WHERE CURRENT OF and
> DELETE WHERE CURRENT OF don't make any sense. (We don't support those
> yet, but we should someday.)

Yes, that's where the positioning makes sense.

> BTW, looking at Date and the SQL spec, I now realize that the recently
> made change to convert FETCH 0 into a no-op is wrong; per spec, FETCH
> RELATIVE 0 means "re-fetch the current row, if any". By analogy, MOVE 0
> should probably return "MOVE 1" if you are on a real row, "MOVE 0" if
> you are not, corresponding to the number of rows you'd have gotten from
> FETCH 0. Ugly, but ...

OK, I will fix those. I am working on it now. I think I am going to
have to break the internal representation that a zero fetch means fetch
all. Right now, we use INT_MAX for fetch all in PerformPortalFetch.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073