AnalysisExpr

vortex_expr

Trait AnalysisExpr 

Source 
pub trait AnalysisExpr {
    // Provided methods
    fn stat_falsification(
        &self,
        _catalog: &mut dyn StatsCatalog,
    ) -> Option<ExprRef> { ... }
    fn max(&self, _catalog: &mut dyn StatsCatalog) -> Option<ExprRef> { ... }
    fn min(&self, _catalog: &mut dyn StatsCatalog) -> Option<ExprRef> { ... }
    fn nan_count(&self, _catalog: &mut dyn StatsCatalog) -> Option<ExprRef> { ... }
    fn field_path(&self) -> Option<FieldPath> { ... }
}
Expand description

This can be used by expression to plug into vortex expression analysis, such as pruning or expression simplification

Provided Methods§

Source

fn stat_falsification(&self, _catalog: &mut dyn StatsCatalog) -> Option<ExprRef>

An expression over zone-statistics which implies all records in the zone evaluate to false.

Given an expression, e, if e.stat_falsification(..) evaluates to true, it is guaranteed that e evaluates to false on all records in the zone. However, the inverse is not necessarily true: even if the falsification evaluates to false, e need not evaluate to true on all records.

The StatsCatalog can be used to constrain or rename stats used in the final expr.

§Examples
  • An expression over one variable: x > 0 is false for all records in a zone if the maximum value of the column x in that zone is less than or equal to zero: max(x) <= 0.
  • An expression over two variables: x > y becomes max(x) <= min(y).
  • A conjunctive expression: x > y AND z < x becomes `max(x) <= min(y) OR min(z) >= max(x).

Some expressions, in theory, have falsifications but this function does not support them such as x < (y < z) or x LIKE "needle%".

Source

fn max(&self, _catalog: &mut dyn StatsCatalog) -> Option<ExprRef>

An expression for the upper non-null bound of this expression, if available.

This function returns None if there is no upper bound or it is difficult to compute.

The returned expression evaluates to null if the maximum value is unknown. In that case, you must not assume the array is empty nor may you assume the array only contains non-null values.

Source

fn min(&self, _catalog: &mut dyn StatsCatalog) -> Option<ExprRef>

An expression for the lower non-null bound of this expression, if available.

See AnalysisExpr::max for important details.

Source

fn nan_count(&self, _catalog: &mut dyn StatsCatalog) -> Option<ExprRef>

An expression for the NaN count for a column, if available.

This method returns None if the NaNCount stat is unknown.

Source

fn field_path(&self) -> Option<FieldPath>

Implementors§