Re: On disable_cost

On Tue, Jul 2, 2024 at 1:40 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> FWIW, I disagree completely.  I think it's entirely natural to
> consider bitmap index scans to be a subset of index scans, so that
> enable_indexscan should affect both.  I admit that the current set
> of GUCs doesn't let you force a bitmap scan over a plain one, but
> I can't recall many people complaining about that.  I don't follow
> the argument that this definition is somehow unmaintainable, either.

Well... but that's not what the GUC does either. Not now, and not with
the patch.

What happens right now is:

- If you set enable_indexscan=false, then disable_cost is added to the
cost of index scan paths and the cost of index-only scan paths.

- If you set enable_indexonlyscan=false, then index-only scan paths
are not generated at all.

Bitmap scans are controlled by enable_bitmapscan.

--
Robert Haas
EDB: http://www.enterprisedb.com