Sqlx: INSERT ... RETURNING id

help
1

TLDR

How can I get the index of a newly-inserted row, using the type-checked sqlx macros?

Details

Comparing sqlx queries with the form

let a = sqlx::query!("INSERT INTO ..."             , ...);
let b = sqlx::query!("INSERT INTO ... RETURNING id", ...);

that is to say, the first merely inserts a row into the table, while the second also returns the new now's index, the types of a and b, as reported by rust-analyzer, are

a: Query<'_, Postgres, PgArguments>
b: Map<'_, Postgres, impl FnMut(PgRow) -> Result<Record, Error>, PgArguments>

respectively.

The Map seems to be this one: Map in sqlx::query - Rust, whose docs state that it

Has most of the same methods as Query but the return types are changed to reflect the mapping. However, there is no equivalent of Query::execute as it doesn’t make sense to map the result type and then ignore it.

From which I infer that I should be using query_as! instead of query!. Fair enough, but query_as! needs a struct specifying the returned type. I this case it should be the type of the index, which is i64, but query_as! rejects it for not being 'a struct, variant or union type'.

2

Use query_scalar! if the row type should be a single value rather than a record type. Or access the id field of the result row(s). Either works.

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