Function diesel::dsl::copy_from

pub fn copy_from<T>(table: T) -> CopyFromQuery<T, NotSet>
where
    T: Table,

Creates a COPY FROM statement

This function constructs COPY FROM statement which copies data from a source into the database. It’s designed to move larger amounts of data into the database.

This function accepts a target table as argument.

There are two ways to construct a COPY FROM statement with diesel:

• By providing a Vec<I> where I implements Insertable for the given table
• By providing a target selection (column list or table name) and a callback that provides the data

The first variant uses the BINARY format internally to send the provided data efficiently to the database. It automatically sets the right options and does not allow changing them. Use CopyFromQuery::from_insertable for this.

The second variant allows you to control the behaviour of the generated COPY FROM statement in detail. It can be setup via the CopyFromQuery::from_raw_data function. The callback accepts an opaque object as argument that allows to write the corresponding data to the database. The exact format depends on the settings chosen by the various CopyFromQuery::with_* methods. See the postgresql documentation for more details about the expected formats.

If you don’t have any specific needs you should prefer using the more convenient first variant.

This functionality is postgresql specific.

Examples

Via CopyFromQuery::from_insertable

#[derive(Insertable)]
#[diesel(table_name = users)]
#[diesel(treat_none_as_default_value = false)]
struct NewUser {
    name: &'static str,
}


let data = vec![
    NewUser { name: "Diva Plavalaguna" },
    NewUser { name: "Father Vito Cornelius" },
];

let count = diesel::copy_from(users::table)
    .from_insertable(&data)
    .execute(connection)?;

assert_eq!(count, 2);

Via CopyFromQuery::from_raw_data

use diesel::pg::CopyFormat;
let count = diesel::copy_from(users::table)
    .from_raw_data(users::table, |copy| {
        writeln!(copy, "3,Diva Plavalaguna").unwrap();
        writeln!(copy, "4,Father Vito Cornelius").unwrap();
        diesel::QueryResult::Ok(())
    })
    .with_format(CopyFormat::Csv)
    .execute(connection)?;

assert_eq!(count, 2);