Enum mz_transform::literal_constraints::IndexMatch

enum IndexMatch {
    Usable(Vec<Row>, bool),
    UnusableTooWide(Vec<MirScalarExpr>),
    UnusableNoSubset,
}

Whether an index is usable to speed up a Filter with literal constraints.

Variants

Usable(Vec<Row>, bool)

The index is usable, that is, each OR argument constrains each key field.

The Vec<Row> has the constraining literal values, where each Row corresponds to one OR argument, and each value in the Row corresponds to one key field.

The bool indicates whether we needed to inverse cast equalities to match them up with key fields. The inverse cast enables index usage when an implicit cast is wrapping a key field. E.g., if a is smallint, and the user writes a = 5, then HIR inserts an implicit cast: smallint_to_integer(a) = 5, which we invert to a = 5, where the 5 is a smallint literal. For more details on the inversion, see invert_casts_on_expr_eq_literal_inner.

UnusableTooWide(Vec<MirScalarExpr>)

The index is unusable. However, there is a subset of key fields such that if the index would be only on this subset, then it would be usable. Note: this Vec is never empty. (If it were empty, then we’d get UnusableNoSubset instead.)

UnusableNoSubset

The index is unusable. Moreover, none of its key fields could be used as an alternate index to speed up this filter.

Trait Implementations

impl Clone for IndexMatch

fn clone(&self) -> IndexMatch

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.