1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191
//! AST types representing various typed SQL expressions. Almost all types //! implement either [`Expression`](/diesel/expression/trait.Expression.html) or //! [`AsExpression`](/diesel/expression/trait.AsExpression.html). //! //! The most common expression to work with is a //! [`Column`](../query_source/trait.Column.html). There are various methods //! that you can call on these, found in //! [`expression_methods`](expression_methods/index.html). You can also call //! numeric operators on types which have been passed to //! [`operator_allowed!`](../macro.operator_allowed.html) or //! [`numeric_expr!`](../macro.numeric_expr.html). //! //! Any primitive which implements [`ToSql`](../types/trait.ToSql.html) will //! also implement [`AsExpression`](trait.AsExpression.html), allowing it to be //! used as an argument to any of the methods described here. #[macro_use] #[doc(hidden)] pub mod ops; #[doc(hidden)] pub mod array_comparison; #[doc(hidden)] pub mod bound; #[doc(hidden)] pub mod coerce; #[doc(hidden)] pub mod count; #[doc(hidden)] pub mod exists; #[doc(hidden)] #[macro_use] pub mod functions; #[doc(hidden)] pub mod grouped; #[macro_use] pub mod helper_types; #[doc(hidden)] pub mod nullable; #[doc(hidden)] #[macro_use] pub mod predicates; pub mod sql_literal; mod unchecked_bind; /// Reexports various top level functions and core extensions that are too /// generic to export by default. This module exists to conveniently glob import /// in functions where you need them. pub mod dsl { #[doc(inline)] pub use super::count::{count, count_star}; #[doc(inline)] pub use super::functions::date_and_time::*; #[doc(inline)] pub use super::functions::aggregate_ordering::*; #[doc(inline)] pub use super::functions::aggregate_folding::*; #[doc(inline)] pub use super::sql_literal::sql; #[doc(inline)] pub use super::exists::exists; #[cfg(feature = "postgres")] pub use pg::expression::dsl::*; } pub use self::dsl::*; pub use self::sql_literal::SqlLiteral; use backend::Backend; /// Represents a typed fragment of SQL. Apps should not need to implement this /// type directly, but it may be common to use this as type boundaries. /// Libraries should consider using /// [`infix_predicate!`](../macro.infix_predicate.html) or /// [`postfix_predicate!`](../macro.postfix_predicate.html) instead of /// implementing this directly. pub trait Expression { type SqlType; } impl<T: Expression + ?Sized> Expression for Box<T> { type SqlType = T::SqlType; } impl<'a, T: Expression + ?Sized> Expression for &'a T { type SqlType = T::SqlType; } /// Describes how a type can be represented as an expression for a given type. /// These types couldn't just implement [`Expression`](trait.Expression.html) /// directly, as many things can be used as an expression of multiple types. /// (`String` for example, can be used as either /// [`VarChar`](../types/type.VarChar.html) or /// [`Text`](../types/struct.Text.html)). /// /// This trait allows us to use primitives on the right hand side of various /// expressions. For example `name.eq("Sean")` pub trait AsExpression<T> { type Expression: Expression<SqlType=T>; fn as_expression(self) -> Self::Expression; } impl<T: Expression> AsExpression<T::SqlType> for T { type Expression = Self; fn as_expression(self) -> Self { self } } /// Indicates that all elements of an expression are valid given a from clause. /// This is used to ensure that `users.filter(posts::id.eq(1))` fails to /// compile. This constraint is only used in places where the nullability of a /// SQL type doesn't matter (everything except `select` and `returning`). For /// places where nullability is important, `SelectableExpression` is used /// instead. pub trait AppearsOnTable<QS: ?Sized>: Expression { } impl<T: ?Sized, QS> AppearsOnTable<QS> for Box<T> where T: AppearsOnTable<QS>, Box<T>: Expression, { } impl<'a, T: ?Sized, QS> AppearsOnTable<QS> for &'a T where T: AppearsOnTable<QS>, &'a T: Expression, { } /// Indicates that an expression can be selected from a source. Columns will /// implement this for their table. Certain special types, like `CountStar` and /// `Bound` will implement this for all sources. Most compound expressions will /// implement this if each of their parts implement it. /// /// Notably, columns will not implement this trait for the right side of a left /// join. To select a column or expression using a column from the right side of /// a left join, you must call `.nullable()` on it. pub trait SelectableExpression<QS: ?Sized>: AppearsOnTable<QS> { } impl<T: ?Sized, QS> SelectableExpression<QS> for Box<T> where T: SelectableExpression<QS>, Box<T>: AppearsOnTable<QS>, { } impl<'a, T: ?Sized, QS> SelectableExpression<QS> for &'a T where T: SelectableExpression<QS>, &'a T: AppearsOnTable<QS>, { } /// Marker trait to indicate that an expression does not include any aggregate /// functions. Used to ensure that aggregate expressions aren't mixed with /// non-aggregate expressions in a select clause, and that they're never /// included in a where clause. pub trait NonAggregate { } impl<T: NonAggregate + ?Sized> NonAggregate for Box<T> { } impl<'a, T: NonAggregate + ?Sized> NonAggregate for &'a T { } use query_builder::{QueryFragment, QueryId}; /// Helper trait used when boxing expressions. This exists to work around the /// fact that Rust will not let us use non-core types as bounds on a trait /// object (you could not return `Box<Expression+NonAggregate>`) pub trait BoxableExpression<QS, DB> where DB: Backend, Self: Expression, Self: SelectableExpression<QS>, Self: NonAggregate, Self: QueryFragment<DB>, {} impl<QS, T, DB> BoxableExpression<QS, DB> for T where DB: Backend, T: Expression, T: SelectableExpression<QS>, T: NonAggregate, T: QueryFragment<DB>, { } impl<QS, ST, DB> QueryId for BoxableExpression<QS, DB, SqlType=ST> { type QueryId = (); fn has_static_query_id() -> bool { false } }