Function projection_schema 

pub fn projection_schema(
    input: &LogicalPlan,
    exprs: &[Expr],
) -> Result<Arc<DFSchema>>

Computes the schema of the result produced by applying a projection to the input logical plan.

Arguments

• input: A reference to the input LogicalPlan for which the projection schema will be computed.
• exprs: A slice of Expr expressions representing the projection operation to apply.

Metadata Handling

• Schema-level metadata: Passed through unchanged from the input schema
• Field-level metadata: Determined by each expression via exprlist_to_fields, which calls Expr::to_field to handle expression-specific metadata (literals, aliases, etc.)

Returns

A Result containing an Arc<DFSchema> representing the schema of the result produced by the projection operation. If the schema computation is successful, the Result will contain the schema; otherwise, it will contain an error.