Re: pg_sequence catalog

Review for pg_sequence catalog

I like this change since it moves all the parts which should be 
transactional to the system catalogs while keeping the only 
non-transactional stuff in the sequence relations.

There was some discussion upthread about more compact representations 
for the sequences, but I feel that is a separate issue mostly unrelated 
to this patch.

I might play around more with it but it seems to work well so far.

As pointed out by Peter this patch also requires the changes to 
pg_upgrade. I have not looked at those patches.

= Functional review

- The patch applies and compiles and seems to work fine after some quick 
manual testing.

- The pg_dump tests fails due to the pg_dump code not being updated. I 
have attached a patch which fixes this.

= Benchmarks

I was a bit worried that the extra syscache lookups might slow down 
nextval(), but I got a measurable speed up on a very simple workload 
which consisted of only calls to nextval() to one sequence. The speedup 
was about 10% on my machine.

= Code

The changes to the code looks generally good.

 > @@ -1155,6 +1156,8 @@ doDeletion(const ObjectAddress *object, int flags)
 >                     else
 >                         heap_drop_with_catalog(object->objectId);
 >                 }
 > +               if (relKind == RELKIND_SEQUENCE)
 > +                   DeleteSequenceTuple(object->objectId);
 >                 break;
 >             }

I think it might be cleaner here to put this as a "else if" just like 
"relKind == RELKIND_INDEX".

= Documentation

The patch does not update catalogs.sgml which it should do.

Andreas