SET type (was Re: WAL versus Postgres)

Tom Lane writes:

> I have just been scanning some of the original Postgres papers
> (in an unsuccessful search to find out how one uses "set" attributes;
> anyone know?)

I've been playing around with that a while ago in the hope that this would
explain this table-as-datatype thing but several findings led me to
believe that this is long dead, removed, rotten code:

* SET uses textin/textout

* no functions defined with SET arguments or return values,
pg_proc.proretset is false for all rows

* the only entry point for defining sets is in parser/parser.c, which is
fittingly marked #ifdef SETS_FIXED


The function SetDefine in utils/adt/sets.c makes me think that a SET is
more or less a stored procedure without arguments. That is, you would
define some SET type in terms of a query from another table and then you
could use predicates like `value in set'. The syntax for this must have
gotten lost in the PostQUEL to SQL switch. All in all there's not much to
rescue from there, I believe.


-- 
Peter Eisentraut                  Sernanders väg 10:115
peter_e@gmx.net                   75262 Uppsala
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