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//! Types in this module are mostly internal and automatically generated. You
//! shouldn't need to interact with these types during normal usage, other than
//! the methods on [`Table`](/diesel/query_source/trait.Table.html)
#[doc(hidden)]
pub mod joins;

use backend::Backend;
use expression::{Expression, SelectableExpression, NonAggregate};
use query_builder::*;
use types::{FromSqlRow, HasSqlType};

pub use self::joins::JoinTo;

/// Trait indicating that a record can be queried from the database. This trait
/// can be derived automatically using `diesel_codegen`. This trait can only be derived for
/// structs, not enums.
pub trait Queryable<ST, DB> where
    DB: Backend + HasSqlType<ST>,
{
    type Row: FromSqlRow<ST, DB>;

    fn build(row: Self::Row) -> Self;
}

#[doc(hidden)]
pub trait QuerySource {
    type FromClause;
    type DefaultSelection: SelectableExpression<Self>;

    fn from_clause(&self) -> Self::FromClause;
    fn default_selection(&self) -> Self::DefaultSelection;
}

/// A column on a database table. Types which implement this trait should have
/// been generated by the [`table!` macro](../macro.table.html).
pub trait Column: Expression {
    type Table: Table;

    fn name() -> &'static str;
}

/// A SQL database table. Types which implement this trait should have been
/// generated by the [`table!` macro](../macro.table.html).
pub trait Table: QuerySource + AsQuery + Sized {
    type PrimaryKey: SelectableExpression<Self> + NonAggregate;
    type AllColumns: SelectableExpression<Self> + NonAggregate;

    fn primary_key(&self) -> Self::PrimaryKey;
    fn all_columns() -> Self::AllColumns;
}

pub trait AppearsInFromClause<QS> {
    type Count;
}

#[allow(missing_debug_implementations, missing_copy_implementations)]
pub struct Never;
#[allow(missing_debug_implementations, missing_copy_implementations)]
pub struct Succ<T>(T);
pub type Once = Succ<Never>;