Re: [PATCHES] Re: BUG #4070: Join more then ~15 tables let postgreSQL produces wrong data

[Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>]

Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
> Tom Lane wrote:
>> Actually rows are supposed to be limited
>> to ~1600 columns, anyway, because of HeapTupleHeader limitations.

> The trick is that that limitation doesn't apply to the intermediate 
> virtual tuples we move around in the executor.

I'm really unwilling to design the system in such a way that whether a
query works depends on whether a particular executor node tries to
materialize tuples or not.

> Enforcing the limit for virtual tuples as well, and checking for the 
> limit in the planner is one option, but it would cripple the ability to 
> join extremely wide tables. For example, if you had 10 tables with 200 
> columns each, you couldn't join them together even for the purposes of 
> COUNT(*).

Huh?  Only if you actually tried to select all the columns.

I still haven't seen the actual bug description come by here, and the
pgsql-bugs archive hasn't got it either.

			regards, tom lane