Re: improving foreign key locks

Florian Pflug <fgp@phlo.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_KEYset.
 

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