pub struct EliminateOuterJoin;
Expand description

Attempt to replace outer joins with inner joins.

Outer joins are typically more expensive to compute at runtime than inner joins and prevent various forms of predicate pushdown and other optimizations, so removing them if possible is beneficial.

Inner joins filter out rows that do match. Outer joins pass rows that do not match padded with nulls. If there is a filter in the query that would filter any such null rows after the join the rows introduced by the outer join are filtered.

For example, in the select ... from a left join b on ... where b.xx = 100;

For rows when b.xx is null (as it would be after an outer join), the b.xx = 100 predicate filters them out and there is no need to produce null rows for output.

Generally, an outer join can be rewritten to inner join if the filters from the WHERE clause return false while any inputs are null and columns of those quals are come from nullable side of outer join.

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Trait Implementations§

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impl Default for EliminateOuterJoin

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fn default() -> EliminateOuterJoin

Returns the “default value” for a type. Read more
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impl OptimizerRule for EliminateOuterJoin

Attempt to eliminate outer joins.

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fn try_optimize( &self, plan: &LogicalPlan, _config: &dyn OptimizerConfig ) -> Result<Option<LogicalPlan>, DataFusionError>

Try and rewrite plan to an optimized form, returning None if the plan cannot be optimized by this rule.
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fn name(&self) -> &str

A human readable name for this optimizer rule
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fn apply_order(&self) -> Option<ApplyOrder>

How should the rule be applied by the optimizer? See comments on ApplyOrder for details. Read more

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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for Twhere U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> Same<T> for T

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type Output = T

Should always be Self
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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<V, T> VZip<V> for Twhere V: MultiLane<T>,

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fn vzip(self) -> V

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