Re: [HACKERS] Re: varchar() troubles

> 
> > Pretty sure only after but it's hard to tell for sure. My trees for 971204
> > and 971222 both core dump on inserts to varchar, but I can't remember what
> > else I was doing with the trees at the time.
> 
> I now recall that the varchar code was broken during this time (for who knows
> how long?), as I discovered when trying to reproduce the tutorial results for
> the documentation.
> 
> The problem was that some things were copied using VARSIZE rather than
> subtracting out VARHDRSZ first (actually, I think it might have use
> sizeof(int) and other dangers too). I patched that near the end of the year
> and my 980101.d tree and 980106.d tree do not exhibit the symptom:
> 
> postgres=> create table t (v varchar(80),i int);
> CREATE
> postgres=> insert into t values ('hi', 1);
> INSERT 643562 1
> postgres=> select * from t;
> v |i
> --+-
> hi|1
> (1 row)

I have found that ExecEvalVar() uses a descriptor that has the attr
length set to the maximum, instead of -1.  The ExecTypeFromTL() comment
says:

/* ----------------------------------------------------------------
 *      ExecTypeFromTL
 *
 *      Currently there are about 4 different places where we create
 *      TupleDescriptors.  They should all be merged, or perhaps
 *      be rewritten to call BuildDesc().
 *

Clearly stating that the tuple descriptors in the system are created in
several places.  Some places have the length set wrong.  I am going to
have to take a look at all those places, and make sure they have
consistent behaviour.

-- 
Bruce Momjian
maillist@candle.pha.pa.us