Trait diesel::prelude::QuerySource

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pub trait QuerySource {
    type FromClause;
    type DefaultSelection: SelectableExpression<Self>;

    // Required methods
    fn from_clause(&self) -> Self::FromClause;
    fn default_selection(&self) -> Self::DefaultSelection;
}
Expand description

Represents a type which can appear in the FROM clause. Apps should not need to concern themselves with this trait.

Types which implement this trait include:

  • Tables generated by the table! macro
  • Internal structs which represent joins
  • A select statement which has had no query builder methods called on it, other than those which can affect the from clause.

Required Associated Types§

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type FromClause

The type returned by from_clause

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type DefaultSelection: SelectableExpression<Self>

The type returned by default_selection

Required Methods§

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fn from_clause(&self) -> Self::FromClause

The actual FROM clause of this type. This is typically only called in QueryFragment implementations.

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fn default_selection(&self) -> Self::DefaultSelection

The default select clause of this type, which should be used if no select clause was explicitly specified. This should always be a tuple of all the desired columns, not star

Object Safety§

This trait is not object safe.

Implementors§

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impl<From> QuerySource for SelectStatement<From>
where From: AsQuerySource, <From::QuerySource as QuerySource>::DefaultSelection: SelectableExpression<Self>,

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type FromClause = <<From as AsQuerySource>::QuerySource as QuerySource>::FromClause

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type DefaultSelection = <<From as AsQuerySource>::QuerySource as QuerySource>::DefaultSelection

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impl<S> QuerySource for Only<S>

Available on crate feature postgres_backend only.
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impl<S> QuerySource for Alias<S>
where Self: Clone, S: AliasSource, S::Target: QuerySource, <S::Target as QuerySource>::DefaultSelection: FieldAliasMapper<S>, <<S::Target as QuerySource>::DefaultSelection as FieldAliasMapper<S>>::Out: SelectableExpression<Self>,

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type FromClause = Alias<S>

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type DefaultSelection = <<<S as AliasSource>::Target as QuerySource>::DefaultSelection as FieldAliasMapper<S>>::Out