Re: [HACKERS] Cached plans and statement generalization - Mailing list pgsql-hackers
On Tue, Apr 25, 2017 at 9:45 AM, Konstantin Knizhnik <k.knizhnik@postgrespro.ru> wrote:
On 25.04.2017 19:12, Serge Rielau wrote:Sorry, I do not completely understand how presence of type modifiers can affect string literals used in query.You will also need to deal with modifiers in types such as VARCHAR(10). Not sure if there are specific functions which can only deal with literals (?) as well.On Apr 25, 2017, at 8:11 AM, Konstantin Knizhnik <k.knizhnik@postgrespro.ru> wrote:Another problem is caused by using integer literals in context where parameters can not be used, for example "order by 1”.
Can you provide me some example?
SELECT ‘hello’::CHAR(10) || ‘World’, 5 + 6;
You can substitute ‘hello’, ‘World’, 5, and 6. But not 10.
Also some OLAP syntax like “rows preceding”
It pretty much boils down to whether you can do some shallow parsing rather than expending the effort to build the parse tree.
Cheers
Serge
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