>
> > They get the location they ask for, or a failure. Hunting around for
> > the new tuple seems like a real waste, and if someone vacuums, it is
> > gone, no?
>
> It is probably worse, since they might even get the wrong row,
> but that's the same in Informix and Oracle.
>
> In Informix:
>
> a: selects rowid
> b: updates row, row grows, does not fit in page, is relocated
> c: inserts rows, pysical location of rowid is reused
> a: selects row by rowid, gets differet row --> bummer
>
In my implementation,scan by old(updated) tupleid fails.
For example,
=> create table t (dt int4);CREATE=> insert into t values (1);INSERT 18601 1=> select ctid,* from t;ctid
|dt-----+--(0,1)|1(1 row)
=> select * from t where ctid='(0,1)';dt-- 1(1 row)
=> update t set dt=2;UPDATE 1=> select * from t where ctid='(0,1)';dt--(0 rows)
In order to get new tids,I provided functions currtid() and currtid2().
=> select currtid2('t','(0,1)');currtid2--------(0,2)(1 row)
=> select * from t where ctid='(0,2)';dt-- 2(1 row)
Of cource,this function is not effective after vacuum.
If you want to detect the change by vacuum,keep oids together with tids.
Regards.
Hiroshi Inoue
Inoue@tpf.co.jp