Re: pg_stat_statements HLD for futur developments

Hello,

> As a new user of PostgreSQL, I have started using pg_stat_statements, and
> was pleased but a little surprised:
>
> First of all, the normalized form of the query string makes it impossible to
> be used in EXPLAIN commands.

Yes, because of the normalization.

> Second, normalized constants and parameters values where missing to be able
> to test optimizations results manually with EXPLAIN.

The normalization is entirely voluntary. Otherwise, probably every query 
would generate a distinct entry, which for a high load system would be a 
very bad idea, and there would be no point to the extension.

Note that with recent pg you can reuse the query with with a PREPARE, and 
then EXPLAIN on the EXECUTE.

   PREPARE foo(INT) AS <the-query-with-its-dollar-vars>;
   EXPLAIN EXECUTE foo(5432);
   EXPLAIN EXECUTE foo(2345);
   DEALLOCATE foo;

> Third, execution plan was not available (making usage of AUTO_EXPLAIN

Yep, but ISTM that the plan might differ depending on the actual values, 
so it would not make much sense to keep it anyway.

-- 
Fabien.