When does sqlx::query crate a Statement

[barsdeveloper]

Hello, I am implementing a new driver for duckdb. I have the basic functionality so far. I wanted to ask you, in which circumstances sqlx creates a prepared Statement. For example sqlx::query, https://docs.rs/sqlx/latest/sqlx/fn.query.html The documentation says: "Execute a single SQL query as a prepared statement (transparently cached)." but it seems from the implementation that it always creates a string sql, never a statement.

sqlx/sqlx-core/src/query.rs

Line 655 in e474be6

pub fn query<DB>(sql: &str) -> Query<'_, DB, <DB as Database>::Arguments<'_>>

In which circumstance does it actually prepare the statement (without explicitly calling .prepare ? The documentations says "transparently cached".

[abonander]

It is up to the database driver. All the existing implementations prepare and cache the statement when it is first executed on a given connection, unless persistent is set to false.

[barsdeveloper]

Thanks for the answer, I see the drivers have a get_or_prepare_statement method that given a string sql returns a statement metadata object. But wouldn't it be much better to make this caching system transparent to the driver and just use the Executor::prepare method. The caching system could be central and the driver would just need to know how to create a prepared statement but it must already do so.

[abonander]

Statements have to be prepared per-connection so it makes the most sense to have the cache in the connection struct. If you figure out a better way to do that, I'm all for discussing it.