在 Rust 中使用 tokio-postgres 调用执行函数之前如何准备查询参数？

Question

I have the following code:

let query = "INSERT INTO users (uuid, pass) VALUES = $1, $2"; 
let statement = db_client.prepare(query).await?
let params = [&user.uuid, &user.pass];
let res = db_client.execute(&statement, params).await?;

Although, I am getting the following error: expected reference &[&dyn ToSql + Sync] .

I've tried setting the params to type "&[&dyn ToSql + Sync]"

let statement: &[&dyn ToSql + Sync] = db_client.prepare(query).await?

but, no avail.

I've also tried using the macro, to_sql_checked.() on the array... but this does not work either.

Regardless, the following code works:

let res = db_client.execute(&statement, &[&user.uuid, &user.pass]).await?;

What is really the difference here? I believe the code would be better if I was able to preassign the query values before sending them. What is the proper way to do this?

Answer 1

This should work:

let query = "INSERT INTO users (uuid, pass) VALUES = $1, $2"; 
let statement = db_client.prepare(query).await?
let params = &[&user.uuid, &user.pass];
let res = db_client.execute(&statement, params).await?;

Note the extra borrow in front of the array assigned to params .

If it doesn't then you have to ascribe the type of params for some reason you did ascribe a type to statement instead‽

let params: &[&dyn ToSql + Sync] = &[&user.uuid, &user.pass];