Re: Cached plans and statement generalization

Hi,

On 2017-04-24 11:46:02 +0300, Konstantin Knizhnik wrote:
> So what I am thinking now is implicit query caching. If the same query with
> different literal values is repeated many times, then we can try to
> generalize this query and replace it with prepared query with
> parameters.

That's not actuall all that easy:
- You pretty much do parse analysis to be able to do an accurate match.
How much overhead is parse analysis vs. planning in your cases?
- The invalidation infrastructure for this, if not tied to to fully
parse-analyzed statements, is going to be hell.
- Migrating to parameters can actually cause significant slowdowns, not
nice if that happens implicitly.

Greetings,

Andres Freund