| From: | Richard Guo <guofenglinux(at)gmail(dot)com> |
|---|---|
| To: | Amit Langote <amitlangote09(at)gmail(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: index paths and enable_indexscan |
| Date: | 2020-04-14 07:12:56 |
| Message-ID: | CAMbWs4-+zTPg8rQUMWwfSpC_heYVsUhHcc7Sf9fvCWKSynpWvA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Apr 14, 2020 at 2:44 PM Amit Langote <amitlangote09(at)gmail(dot)com>
wrote:
> Hi,
>
> Maybe I am missing something obvious, but is it intentional that
> enable_indexscan is checked by cost_index(), that is, *after* creating
> an index path? I was expecting that if enable_indexscan is off, then
> no index paths would be generated to begin with, because I thought
> they are optional.
>
I think the cost estimate of index paths is the same as other paths on
that setting enable_xxx to off only adds a penalty factor (disable_cost)
to the path's cost. The path would be still generated and compete with
other paths in add_path().
Thanks
Richard
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