Re: improving foreign key locks

Florian Pflug <fgp(at)phlo(dot)org> writes:
> On Dec1, 2010, at 17:17 , Tom Lane wrote:
>> There's not enough space in the infomask to record which columns (or
>> which unique index) are involved. And if you're talking about data that
>> could remain on disk long after the unique index is gone, that's not
>> going to be good enough.

> We'd distinguish two cases
> A) The set of locked columns is a subset of the set of columns mentioned in
> *any* unique index. (In other words, for every locked column there is a
> unique index which includes that column, though not necessarily one index
> which includes them all)
> B) The set of locked columns does not satisfy (A)

How's that fix it? The on-disk flags are still falsifiable by
subsequent index changes.

> Creating indices shouldn't pose a problem, since it would only enlarge the set of locked columns for rows with HEAP_XMAX_SHARED_LOCK_KEY set.

Not with that definition. I could create a unique index that doesn't
contain some column that every previous unique index contained.

regards, tom lane