Re: Cached plans and statement generalization

On 04/25/2017 11:40 PM, Serge Rielau wrote:
>
>> On Apr 25, 2017, at 1:37 PM, Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru <mailto:k(dot)knizhnik(at)postgrespro(dot)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