Horton

Re: On disable_cost

Greg Sabino Mullane <htamfids@gmail.com>

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From: Greg Sabino Mullane <htamfids@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Zhenghua Lyu <zlyu@vmware.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-04-03T20:03:44Z
Lists: pgsql-hackers 
On Wed, Apr 3, 2024 at 3:21 PM Robert Haas <robertmhaas@gmail.com> wrote:

> It's also pretty clear to me that the fact that enable_indexscan
> and enable_indexonlyscan work completely differently from each other
> is surprising at best, wrong at worst, but here again, what this patch
> does about that is not above reproach.


Yes, that is wrong, surely there is a reason we have two vars. Thanks for
digging into this: if nothing else, the code will be better for this
discussion, even if we do nothing for now with disable_cost.

Cheers,
Greg

Commits

  1. Doc: add detail about EXPLAIN's "Disabled" property

  2. Adjust EXPLAIN's output for disabled nodes

  3. Fix order of parameters in a cost_sort call

  4. Show number of disabled nodes in EXPLAIN ANALYZE output.

  5. Treat number of disabled nodes in a path as a separate cost metric.

  6. Remove grotty use of disable_cost for TID scan plans.