Re: index-only scans

On Fri, Oct 7, 2011 at 11:40 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> Please find attached a patch implementing a basic version of
>> index-only scans.
>
> I'm making some progress with this, but I notice what seems like a
> missing feature: there needs to be a way to turn it off.  Otherwise
> performance comparisons will be difficult to impossible.
>
> The most obvious solution is a planner control GUC, perhaps
> "enable_indexonlyscan".  Anyone object, or want to bikeshed the name?
>

Currently I can't force an indexonlyscan over an indexscan, because of
the way the enable_* variables work.

Should setting enable_indexscan=off also disable index-only scans (the
current behavior) in addition to plain index scans?

By way of precedent, enable_indexscan=off does not disable Bitmap Index Scan.

Cheers,

Jeff