Re: User Defined Functions/AM's inherently slow?

On Jan 17, 2004, at 10:22 PM, Tom Lane wrote:

> Eric Ridge <ebr@tcdi.com> writes:
>> I've created a stub AM that literally does nothing.
>
> It's not possible for an index AM to "do nothing", at least not for an
> indexscan.  It has to return tuple pointers.  What are you doing for
> that?

costestimate: {PG_RETURN_VOID();
}

beginscan: {Relation index = (Relation) PG_GETARG_POINTER(0);int keysz = PG_GETARG_INT32(1);ScanKey    scankey =
(ScanKey)PG_GETARG_POINTER(2);IndexScanDesc scan = RelationGetIndexScan(index, keysz, scankey);
 
PG_RETURN_POINTER(scan);
}

rescan: {PG_RETURN_VOID();
}

gettuple: {PG_RETURN_BOOL(false);
}

endscan: {PG_RETURN_VOID();
}

I think the above is about as close to "nothing" as one can get.

In trying to track down some performance issues with my real AM, I 
decided to make this stub AM just to see what the overhead is... then I 
started seeing these crazy results.

eric