Re: [HACKERS] Cached plans and statement generalization

On Apr 25, 2017, at 1:37 PM, Konstantin Knizhnik <k.knizhnik@postgrespro.ru> wrote:

SELECT ‘hello’::CHAR(10) || ‘World’, 5 + 6;

You can substitute ‘hello’, ‘World’, 5, and 6. But not 10.

I am substituting only string literals. So the query above will be transformed to

SELECT $1::CHAR(10) || $2, 5 + 6;

What's wrong with it?

Oh, well that leaves a lot of opportunities on the table, doesn’t it?

Well, actually my primary intention was not to make badly designed programs (not using prepared statements) work faster.
I wanted to address cases when it is not possible to use prepared statements.
If we want to substitute with parameters as much literals as possible, then parse+deparse tree seems to be the only reasonable approach.
I will try to implement it also, just to estimate parsing overhead.

Cheers

Serge

-- 
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company