ExprSimplifier::coerce limits the applicability of containment PruningPredicates (LiteralGuarantee::analyze`)

[joseph-isaacs]

Is your feature request related to a problem or challenge?

I am trying to use PruningPredicates.

The expressions require coercion ExprSimplifier::coerce before it can be evaluated, so we run [simplify, coerce, simplify, create_physical_expr, PruningPredicate::try_new].

If the expression being considered (with schema) is: Col('y', Int32) = Lit(Int64(5)) then the resulting expression will be.

BinaryExpr {
    left: Cast(
        Cast {
            expr: Column(
                Column {
                    relation: None,
                    name: "y",
                },
            ),
            data_type: Int64,
        },
    ),
    op: Eq,
    right: Literal(
        Int64(5),
    ),
}

Then when PruningPredicate analysis is run the LiteralGuarantee::analyze will not find any LiteralGuarantees and therefore pruning will safely assume that nothing can be pruned.

However if the expression is Col('y', Int32) = Lit(Int32(5)), no cast will be included and pruning will work as indented.

Describe the solution you'd like

Either:

• expand LiteralGuarantee::analyze to understand Casting
• extend ExprSimplifier::coerce to safely downcast Literals (in Lit <op> Col) to the column type if possible Lit(Int64(2)) -> Lit(Int16(2)).
• or add another pass to downcast all literals (where lossless) so that coercion is applied to the literal and therefore folded into the literal.

Describe alternatives you've considered

No response

Additional context

Relevant issues: #8302

[eejbyfeldt]

or add another pass to downcast all literals (where lossless) so that coercion is applied to the literal and therefore folded into the literal.

Maybe I am not fully understanding the ask here, but does this not already exists as the optimizer pass UnwrapCastInComparision?

[joseph-isaacs]

This is great thanks.

We are only using expressions not plans. Do you think we could make struct UnwrapCastExprRewriter public?