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joins.rs
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joins.rs
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use super::{AppearsInFromClause, Plus, QuerySource};
use crate::backend::Backend;
use crate::backend::DieselReserveSpecialization;
use crate::expression::grouped::Grouped;
use crate::expression::nullable::Nullable;
use crate::expression::SelectableExpression;
use crate::prelude::*;
use crate::query_builder::*;
use crate::query_dsl::InternalJoinDsl;
use crate::result::QueryResult;
use crate::sql_types::BoolOrNullableBool;
use crate::util::TupleAppend;
/// A query source representing the join between two tables
pub struct Join<Left: QuerySource, Right: QuerySource, Kind> {
left: FromClause<Left>,
right: FromClause<Right>,
kind: Kind,
}
impl<Left, Right, Kind> Clone for Join<Left, Right, Kind>
where
Left: QuerySource,
FromClause<Left>: Clone,
Right: QuerySource,
FromClause<Right>: Clone,
Kind: Clone,
{
fn clone(&self) -> Self {
Self {
left: self.left.clone(),
right: self.right.clone(),
kind: self.kind.clone(),
}
}
}
impl<Left, Right, Kind> Copy for Join<Left, Right, Kind>
where
Left: QuerySource,
FromClause<Left>: Copy,
Right: QuerySource,
FromClause<Right>: Copy,
Kind: Copy,
{
}
impl<Left, Right, Kind> std::fmt::Debug for Join<Left, Right, Kind>
where
Left: QuerySource,
FromClause<Left>: std::fmt::Debug,
Right: QuerySource,
FromClause<Right>: std::fmt::Debug,
Kind: std::fmt::Debug,
{
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("Join")
.field("left", &self.left)
.field("right", &self.right)
.field("kind", &self.kind)
.finish()
}
}
impl<Left, Right, Kind> QueryId for Join<Left, Right, Kind>
where
Left: QueryId + QuerySource + 'static,
Right: QueryId + QuerySource + 'static,
Kind: QueryId,
{
type QueryId = Join<Left, Right, Kind::QueryId>;
const HAS_STATIC_QUERY_ID: bool =
Left::HAS_STATIC_QUERY_ID && Right::HAS_STATIC_QUERY_ID && Kind::HAS_STATIC_QUERY_ID;
}
#[derive(Debug, Clone, Copy, QueryId)]
#[doc(hidden)]
/// A query source representing the join between two tables with an explicit
/// `ON` given. `Join` should usually be referenced instead, as all "type
/// safety" traits are implemented in terms of `Join` implementing them.
pub struct JoinOn<Join, On> {
join: Join,
on: On,
}
impl<Left, Right, Kind> Join<Left, Right, Kind>
where
Left: QuerySource,
Right: QuerySource,
{
pub(crate) fn new(left: Left, right: Right, kind: Kind) -> Self {
Join {
left: FromClause::new(left),
right: FromClause::new(right),
kind,
}
}
pub(crate) fn on<On>(self, on: On) -> JoinOn<Self, On> {
JoinOn { join: self, on: on }
}
}
impl<Left, Right> QuerySource for Join<Left, Right, Inner>
where
Left: QuerySource + AppendSelection<Right::DefaultSelection>,
Right: QuerySource,
Left::Output: SelectableExpression<Self>,
Self: Clone,
{
type FromClause = Self;
type DefaultSelection = Left::Output;
fn from_clause(&self) -> Self::FromClause {
self.clone()
}
fn default_selection(&self) -> Self::DefaultSelection {
self.left
.source
.append_selection(self.right.source.default_selection())
}
}
impl<Left, Right> QuerySource for Join<Left, Right, LeftOuter>
where
Left: QuerySource + AppendSelection<Nullable<Right::DefaultSelection>>,
Right: QuerySource,
Left::Output: SelectableExpression<Self>,
Self: Clone,
{
type FromClause = Self;
type DefaultSelection = Left::Output;
fn from_clause(&self) -> Self::FromClause {
self.clone()
}
fn default_selection(&self) -> Self::DefaultSelection {
self.left
.source
.append_selection(self.right.source.default_selection().nullable())
}
}
#[derive(Debug, Clone, Copy)]
pub struct OnKeyword;
impl<DB: Backend> nodes::MiddleFragment<DB> for OnKeyword {
fn push_sql(&self, mut pass: AstPass<'_, '_, DB>) {
pass.push_sql(" ON ");
}
}
impl<Join, On> QuerySource for JoinOn<Join, On>
where
Join: QuerySource,
On: AppearsOnTable<Join::FromClause> + Clone,
On::SqlType: BoolOrNullableBool,
Join::DefaultSelection: SelectableExpression<Self>,
{
type FromClause = Grouped<nodes::InfixNode<Join::FromClause, On, OnKeyword>>;
type DefaultSelection = Join::DefaultSelection;
fn from_clause(&self) -> Self::FromClause {
Grouped(nodes::InfixNode::new(
self.join.from_clause(),
self.on.clone(),
OnKeyword,
))
}
fn default_selection(&self) -> Self::DefaultSelection {
self.join.default_selection()
}
}
impl<Left, Right, Kind, DB> QueryFragment<DB> for Join<Left, Right, Kind>
where
DB: Backend + DieselReserveSpecialization,
Left: QuerySource,
Left::FromClause: QueryFragment<DB>,
Right: QuerySource,
Right::FromClause: QueryFragment<DB>,
Kind: QueryFragment<DB>,
{
fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
self.left.from_clause.walk_ast(out.reborrow())?;
self.kind.walk_ast(out.reborrow())?;
out.push_sql(" JOIN ");
self.right.from_clause.walk_ast(out.reborrow())?;
Ok(())
}
}
/// Indicates that two tables can be joined without an explicit `ON` clause.
///
/// Implementations of this trait are generated by invoking [`joinable!`].
/// Implementing this trait means that you can call
/// `left_table.inner_join(right_table)`, without supplying the `ON` clause
/// explicitly. To join two tables which do not implement this trait, you will
/// need to call [`.on`].
///
/// See [`joinable!`] and [`inner_join`] for usage examples.
///
/// [`joinable!`]: crate::joinable!
/// [`.on`]: crate::query_dsl::JoinOnDsl::on()
/// [`inner_join`]: crate::query_dsl::QueryDsl::inner_join()
pub trait JoinTo<T> {
#[doc(hidden)]
type FromClause;
#[doc(hidden)]
type OnClause;
#[doc(hidden)]
fn join_target(rhs: T) -> (Self::FromClause, Self::OnClause);
}
#[doc(hidden)]
/// Used to ensure the sql type of `left.join(mid).join(right)` is
/// `(Left, Mid, Right)` and not `((Left, Mid), Right)`. This needs
/// to be separate from `TupleAppend` because we still want to keep
/// the column lists (which are tuples) separate.
pub trait AppendSelection<Selection> {
type Output;
fn append_selection(&self, selection: Selection) -> Self::Output;
}
impl<T: Table, Selection> AppendSelection<Selection> for T {
type Output = (T::AllColumns, Selection);
fn append_selection(&self, selection: Selection) -> Self::Output {
(T::all_columns(), selection)
}
}
impl<Left, Mid, Selection, Kind> AppendSelection<Selection> for Join<Left, Mid, Kind>
where
Left: QuerySource,
Mid: QuerySource,
Self: QuerySource,
<Self as QuerySource>::DefaultSelection: TupleAppend<Selection>,
{
type Output = <<Self as QuerySource>::DefaultSelection as TupleAppend<Selection>>::Output;
fn append_selection(&self, selection: Selection) -> Self::Output {
self.default_selection().tuple_append(selection)
}
}
impl<Join, On, Selection> AppendSelection<Selection> for JoinOn<Join, On>
where
Join: AppendSelection<Selection>,
{
type Output = Join::Output;
fn append_selection(&self, selection: Selection) -> Self::Output {
self.join.append_selection(selection)
}
}
#[doc(hidden)]
#[derive(Debug, Clone, Copy, Default, QueryId)]
pub struct Inner;
impl<DB> QueryFragment<DB> for Inner
where
DB: Backend + DieselReserveSpecialization,
{
fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
out.push_sql(" INNER");
Ok(())
}
}
#[doc(hidden)]
#[derive(Debug, Clone, Copy, Default, QueryId)]
pub struct LeftOuter;
impl<DB> QueryFragment<DB> for LeftOuter
where
DB: Backend + DieselReserveSpecialization,
{
fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
out.push_sql(" LEFT OUTER");
Ok(())
}
}
impl<Left, Mid, Right, Kind> JoinTo<Right> for Join<Left, Mid, Kind>
where
Left: JoinTo<Right> + QuerySource,
Mid: QuerySource,
{
type FromClause = <Left as JoinTo<Right>>::FromClause;
type OnClause = Left::OnClause;
fn join_target(rhs: Right) -> (Self::FromClause, Self::OnClause) {
Left::join_target(rhs)
}
}
impl<Join, On, Right> JoinTo<Right> for JoinOn<Join, On>
where
Join: JoinTo<Right>,
{
type FromClause = Join::FromClause;
type OnClause = Join::OnClause;
fn join_target(rhs: Right) -> (Self::FromClause, Self::OnClause) {
Join::join_target(rhs)
}
}
impl<T, Left, Right, Kind> AppearsInFromClause<T> for Join<Left, Right, Kind>
where
Left: AppearsInFromClause<T> + QuerySource,
Right: AppearsInFromClause<T> + QuerySource,
Left::Count: Plus<Right::Count>,
{
type Count = <Left::Count as Plus<Right::Count>>::Output;
}
impl<T, Join, On> AppearsInFromClause<T> for JoinOn<Join, On>
where
Join: AppearsInFromClause<T>,
{
type Count = Join::Count;
}
#[doc(hidden)]
#[derive(Debug, Clone, Copy)]
pub struct OnClauseWrapper<Source, On> {
pub(crate) source: Source,
pub(crate) on: On,
}
impl<Source, On> OnClauseWrapper<Source, On> {
pub fn new(source: Source, on: On) -> Self {
OnClauseWrapper { source, on }
}
}
impl<Lhs, Rhs, On> JoinTo<OnClauseWrapper<Rhs, On>> for Lhs
where
Lhs: Table,
{
type FromClause = Rhs;
type OnClause = On;
fn join_target(rhs: OnClauseWrapper<Rhs, On>) -> (Self::FromClause, Self::OnClause) {
(rhs.source, rhs.on)
}
}
impl<Lhs, Rhs, On> JoinTo<Rhs> for OnClauseWrapper<Lhs, On>
where
Lhs: JoinTo<Rhs>,
{
type FromClause = <Lhs as JoinTo<Rhs>>::FromClause;
type OnClause = <Lhs as JoinTo<Rhs>>::OnClause;
fn join_target(rhs: Rhs) -> (Self::FromClause, Self::OnClause) {
<Lhs as JoinTo<Rhs>>::join_target(rhs)
}
}
impl<Rhs, Kind, On1, On2, Lhs> InternalJoinDsl<Rhs, Kind, On1> for OnClauseWrapper<Lhs, On2>
where
Lhs: InternalJoinDsl<Rhs, Kind, On1>,
{
type Output = OnClauseWrapper<<Lhs as InternalJoinDsl<Rhs, Kind, On1>>::Output, On2>;
fn join(self, rhs: Rhs, kind: Kind, on: On1) -> Self::Output {
OnClauseWrapper {
source: self.source.join(rhs, kind, on),
on: self.on,
}
}
}
impl<Qs, On> QueryDsl for OnClauseWrapper<Qs, On> {}
#[doc(hidden)]
/// Convert any joins in a `FROM` clause into an inner join.
///
/// This trait is used to determine whether
/// `Nullable<T>: SelectableExpression<SomeJoin>`. We consider it to be
/// selectable if `T: SelectableExpression<InnerJoin>`. Since `SomeJoin`
/// may be deeply nested, we need to recursively change any appearances of
/// `LeftOuter` to `Inner` in order to perform this check.
pub trait ToInnerJoin {
type InnerJoin;
}
impl<Left, Right, Kind> ToInnerJoin for Join<Left, Right, Kind>
where
Left: ToInnerJoin + QuerySource,
Left::InnerJoin: QuerySource,
Right: ToInnerJoin + QuerySource,
Right::InnerJoin: QuerySource,
{
type InnerJoin = Join<Left::InnerJoin, Right::InnerJoin, Inner>;
}
impl<Join, On> ToInnerJoin for JoinOn<Join, On>
where
Join: ToInnerJoin,
{
type InnerJoin = JoinOn<Join::InnerJoin, On>;
}
impl<From> ToInnerJoin for SelectStatement<FromClause<From>>
where
From: ToInnerJoin + QuerySource,
From::InnerJoin: QuerySource,
{
type InnerJoin = SelectStatement<FromClause<From::InnerJoin>>;
}
impl<T: Table> ToInnerJoin for T {
type InnerJoin = T;
}