Re: Revisiting pg_stat_statements and IN() (Was: Re: pg_stat_statements fingerprinting logic and ArrayExpr)

On Mon, Nov 23, 2015 at 11:53 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:

> One specific justification he gave for not using pg_stat_statements was:
>
> "Doesn’t merge bind vars in IN()" (See slide #11)
>
> I wonder:
>
> * How do other people feel about this? Personally, I've seen enough
> problems of this kind in the field that "slippery slope" arguments
> against this don't seem very compelling.
>

As someone who runs a little monitoring service thats solely based on
pg_stat_statements data, ignoring IN list length would certainly be a good
change.

We currently do this in post-processing, together with other data cleanup
(e.g. ignoring the length of a VALUES list in an INSERT statement).

Given the fact that pgss data is normalized & you don't know which plan was
chosen, I don't think distinguishing based on the length of the list helps
anyone really.

I see pg_stat_statements as a high-level overview of which queries have
run, and which ones you might want to look into closer using e.g.
auto_explain.

Best,
Lukas

--
Lukas Fittl

Skype: lfittl
Phone: +1 415 321 0630