Great, thank you both for the info.
On 8/6/24 22:25, Tom Lane wrote:
> Maciek Sakrejda writes:
>> In a blog post [1], Bruce Momjian notes that expression indexes can
>> help with planning even if they're not used directly. But the examples
>> cited in that post are vague (i.e., they improve stats, but it's not
>> clear how they coul
Maciek Sakrejda writes:
> Thanks, but I was asking specifically about _unused_ indexes
> (according to pg_stat_user_indexes). Bruce's blog post showed how they
> can still influence rowcount estimates, but can they do that (1) even
> if they don't end up being used by the query plan and (2) in a w
On Tue, Aug 6, 2024 at 1:25 PM Tom Lane wrote:
> The planner has no info about the values of sqrt(x1), so you get a
> default estimate (one-third) of the selectivity of the WHERE clause.
> But watch this:
>
> regression=# create index on foo (sqrt(x1));
> CREATE INDEX
> regression=# analyze foo;
>
Maciek Sakrejda writes:
> In a blog post [1], Bruce Momjian notes that expression indexes can
> help with planning even if they're not used directly. But the examples
> cited in that post are vague (i.e., they improve stats, but it's not
> clear how they could change plans), and Bruce's answer to
