Function join_alias_input_schemas 

pub fn join_alias_input_schemas(
    kind: JoinKind,
    left: &RowSchema,
    right: &RowSchema,
    using: Option<&ResolvedJoinUsing>,
    alias: &str,
    column_aliases: &[String],
) -> Result<(RowSchema, RowSchema), SQLError>

Add a parenthesized JOIN alias to the input-side schemas for null-rejection analysis. Merged FULL JOIN columns belong to neither side exclusively because their value is a coalesce of both inputs.