Trait mz_expr::interpret::Interpreter

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pub trait Interpreter {
    type Summary: Clone + Debug + Sized;

    // Required methods
    fn column(&self, id: usize) -> Self::Summary;
    fn literal(
        &self,
        result: &Result<Row, EvalError>,
        col_type: &ColumnType,
    ) -> Self::Summary;
    fn unmaterializable(&self, func: &UnmaterializableFunc) -> Self::Summary;
    fn unary(&self, func: &UnaryFunc, expr: Self::Summary) -> Self::Summary;
    fn binary(
        &self,
        func: &BinaryFunc,
        left: Self::Summary,
        right: Self::Summary,
    ) -> Self::Summary;
    fn variadic(
        &self,
        func: &VariadicFunc,
        exprs: Vec<Self::Summary>,
    ) -> Self::Summary;
    fn cond(
        &self,
        cond: Self::Summary,
        then: Self::Summary,
        els: Self::Summary,
    ) -> Self::Summary;

    // Provided methods
    fn expr(&self, expr: &MirScalarExpr) -> Self::Summary { ... }
    fn mfp_filter(&self, mfp: &MapFilterProject) -> Self::Summary { ... }
    fn mfp_plan_filter(&self, plan: &MfpPlan) -> Self::Summary { ... }
}
Expand description

Abstract interpretation for MirScalarExpr.

MirScalarExpr::eval implements a “concrete interpreter” for the expression type: given an expression and specific column values as input, it returns a specific value for the output. This could be reimplemented using this trait… but it’s most useful for “abstract” interpretations of the expression, where we generalize about sets of possible inputs and outputs. See Trace and ColumnSpecs for how this can be useful in practice.

Required Associated Types§

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type Summary: Clone + Debug + Sized

Required Methods§

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fn column(&self, id: usize) -> Self::Summary

A column of the input row.

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fn literal( &self, result: &Result<Row, EvalError>, col_type: &ColumnType, ) -> Self::Summary

A literal value. (Stored as a row, because we can’t own a Datum.)

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fn unmaterializable(&self, func: &UnmaterializableFunc) -> Self::Summary

A call to an unmaterializable function.

These functions cannot be evaluated by MirScalarExpr::eval. They must be transformed away by a higher layer.

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fn unary(&self, func: &UnaryFunc, expr: Self::Summary) -> Self::Summary

A function call that takes one expression as an argument.

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fn binary( &self, func: &BinaryFunc, left: Self::Summary, right: Self::Summary, ) -> Self::Summary

A function call that takes two expressions as arguments.

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fn variadic( &self, func: &VariadicFunc, exprs: Vec<Self::Summary>, ) -> Self::Summary

A function call that takes an arbitrary number of arguments.

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fn cond( &self, cond: Self::Summary, then: Self::Summary, els: Self::Summary, ) -> Self::Summary

Conditionally evaluated expressions.

Provided Methods§

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fn expr(&self, expr: &MirScalarExpr) -> Self::Summary

Evaluate an entire expression, by delegating to the fine-grained methods on Interpreter.

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fn mfp_filter(&self, mfp: &MapFilterProject) -> Self::Summary

Specifically, this evaluates the map and filters stages of an MFP: summarize each of the map expressions, then and together all of the filters.

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fn mfp_plan_filter(&self, plan: &MfpPlan) -> Self::Summary

Similar to Self::mfp_filter, but includes the additional temporal filters that have been broken out.

Implementors§