Re: pg_stat_statements and "IN" conditions

On 2023-Feb-09, Dmitry Dolgov wrote:

> > On Thu, Feb 09, 2023 at 02:30:34PM +0100, Peter Eisentraut wrote:

> > What is the point of making this a numeric setting? Either you want
> > to merge all values or you don't want to merge any values.
>
> At least in theory the definition of "too many constants" is different
> for different use cases and I see allowing to configure it as a way of
> reducing the level of surprise here.

I was thinking about this a few days ago and I agree that we don't
necessarily want to make it just a boolean thing; we may want to make it
more complex. One trivial idea is to make it group entries in powers of
10: for 0-9 elements, you get one entry, and 10-99 you get a different
one, and so on:

# group everything in a single bucket
const_merge_threshold = true / yes / on

# group 0-9, 10-99, 100-999, 1000-9999
const_merge_treshold = powers

Ideally the value would be represented somehow in the query text. For
example

query | calls
----------------------------------------------------------+-------
select * from test where i in ({... 0-9 entries ...}) | 2
select * from test where i in ({... 10-99 entries ...}) | 1

What do you think? The jumble would have to know how to reduce all
values within each power-of-ten group to one specific value, but I don't
think that should be particularly difficult.

--
Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/
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