Re: Arrays vs separate system catalogs

Tom Lane wrote:
> Peter Eisentraut <peter_e@gmx.net> writes:
> 
>>During my coding of the per-user/database settings, it occurred to me one
>>more time that arrays are evil.  Basically, the initial idea was to have a
>>column pg_database.datconfig that contains, say,
>>'{"geqo_threshold=55","enable_seqscan=off"}'.  Just inserting and deleting
>>in arrays is terrible, let alone querying them in a reasonable manner.
>>We're getting killed by this every day in the privileges and groups case.
>>
> 
>>What are people's thoughts on where (variable-length) arrays are OK in
>>system catalogs, and where a new system catalog should be created?
>>
> 
> Seems like an array is a perfectly fine representation, and what's
> lacking are suitable operators.  Maybe we should think about inventing
> some operators, rather than giving up on arrays.

IMHO making arrays and relations equivalent is a real challenge. But 
this would give the full power of SQL to arrays (subselects, aggregates, 
  easy insertion, deletion, selection, updates).

But if you manage to make an array accessible as a relation this would 
be a big step for mankind ;-)

(e.g. select * from pg_class.relacl where pg_class.relname='pg_stats';

insert into pg_class.relacl values 'christof=r' where 
pg_class.relname='pg_stats';

But at least the second example looks unSQLish to me
(I doubt the syntax "insert ... where" is legal))

Seemed a good idea first ... but I don't know whether it is worth the 
(syntactic, planning, non-standard) trouble.
     Christof Petig