Struct mz_expr::Trace

pub struct Trace;

An interpreter that returns whether or not a particular expression is “pushdownable”. Broadly speaking, an expression is pushdownable if the result of evaluating the expression depends on the range of possible column values in a way that ColumnSpecs is able to reason about.

In practice, we internally need to distinguish between expressions that are trivially predicable (because they’re constant) and expressions that depend on the column ranges themselves. See the TraceSummary variants for those distinctions, and TraceSummary::pushdownable for the overall assessment.

Trait Implementations

impl Debug for Trace

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Interpreter for Trace

type Summary = TraceSummary

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

A column of the input row.

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.)

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

A call to an unmaterializable function.

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

A function call that takes one expression as an argument.

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

A function call that takes two expressions as arguments.

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

A function call that takes an arbitrary number of arguments.

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

Conditionally evaluated expressions.

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

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

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.

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.