Re: vacuumlo issue

MUHAMMAD ASIF <anaeem.it@hotmail.com> writes:
> We have noticed the following issue with vacuumlo database that have millions of record in pg_largeobject i.e.
>    WARNING:  out of shared memoryFailed to remove lo 155987:    ERROR:  out of shared memory   HINT:  You might need
toincrease max_locks_per_transaction.
 
> Why do we need to increase max_locks_per_transaction/shared memory for
> clean up operation,

This seems to be a consequence of the 9.0-era decision to fold large
objects into the standard dependency-deletion algorithm and hence
take out locks on them individually.

I'm not entirely convinced that that was a good idea.  However, so far
as vacuumlo is concerned, the only reason this is a problem is that
vacuumlo goes out of its way to do all the large-object deletions in a
single transaction.  What's the point of that?  It'd be useful to batch
them, probably, rather than commit each deletion individually.  But the
objects being deleted are by assumption unreferenced, so I see no
correctness argument why they should need to go away all at once.
        regards, tom lane