如何将间隔参数传递给准备好的语句？

Question

I want to delete all database entries in my Postgres database that are older than X minutes. My prepared statement in go looks like this:

delete
from my_table
where expires < (to_timestamp($1) - '$2 minutes'::interval);

How can I correctly pass the second parameter $2 ?

---

PS: I know there's different statements to solve the problem, but I am explicitly interested in how to pass parameters that are quoted.

Answer 1

You can cast the parameter to text and then concatenate it with the string ' minutes' .

delete from my_table
where expires < (to_timestamp($1) - ($2::text || ' minutes')::interval

UPDATE: actually, since postgres does have a any || text any || text operator, the result of which is text , you shouldn't need to type cast the parameter.

Answer 2

There is no way to interpolate a parameter into a string literal.

A possible solution for your case would be to multiply a number with an interval:

where expires < (to_timestamp($1) - $2 * '1 minute'::interval)

Answer 3

You can use make_interval

delete from my_table
where expires < (to_timestamp($1) - make_interval(mins => $2));

Answer 4

You can also parametrize the entire interval string instead. This removes the need for an intermediate cast to text and concat.

query := `
  delete from my_table
  where expires < (to_timestamp($1) - $2::interval);
`
interval := fmt.Sprintf("%d minutes", mins)
db.Exec(query, timestamp, interval)