alamb commented on code in PR #5675:
URL: https://github.com/apache/arrow-datafusion/pull/5675#discussion_r1155962533
##########
datafusion/expr/src/expr_schema.rs:
##########
@@ -39,6 +40,13 @@ pub trait ExprSchemable {
/// cast to a type with respect to a schema
fn cast_to<S: ExprSchema>(self, cast_to_type: &DataType, schema: &S) ->
Result<Expr>;
+
+ /// promote to a type with respect to a schema
Review Comment:
Can you please add some comments to clarify what the difference between
"promote" and "cast" is?
##########
datafusion/expr/src/expr.rs:
##########
@@ -385,6 +408,20 @@ impl Cast {
}
}
+/// Cast expression
Review Comment:
Can we please add documentation about what `PromotePrecision` does and in
what circumstances it is needed?
##########
datafusion/expr/src/expr.rs:
##########
@@ -234,12 +236,33 @@ pub struct BinaryExpr {
pub op: Operator,
/// Right-hand side of the expression
pub right: Box<Expr>,
+ /// The data type of the expression, if known
Review Comment:
I don't understand the reason for this change -- is it no longer possible to
calculate the output type of a `BinaryExpr` from its inputs?
If the desired output type is different then couldn't we `cast` the expr to
the type?
##########
datafusion/core/tests/sqllogictests/test_files/tpch.slt:
##########
@@ -125,7 +125,7 @@ select
sum(l_quantity) as sum_qty,
sum(l_extendedprice) as sum_base_price,
sum(l_extendedprice * (1 - l_discount)) as sum_disc_price,
- sum(l_extendedprice * (1 - l_discount) * (1 + l_tax)) as sum_charge,
+ sum(cast(l_extendedprice as decimal(12,2)) * (1 - l_discount) * (1 +
l_tax)) as sum_charge,
Review Comment:
perhaps we can add a comment here referencing the new arrow-rs kernel /
work. Otherwise this context will likely get forgotten
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