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 field_path(&self) -> Option<AccessPath> { ... }
}
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>

If an expression is returned, its value is an upper bound on the value of expr.

We may return None for values which have no upper bound or values for which knowing the upper bound is difficult.

Source

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

If an expression is returned, its value is an upper bound on the value of expr. see AnalysisExpr::max

Source

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

Implementors§