alamb commented on code in PR #11797:
URL: https://github.com/apache/datafusion/pull/11797#discussion_r1706039120
##########
datafusion/expr/src/udf.rs:
##########
@@ -345,12 +351,22 @@ pub trait ScalarUDFImpl: Debug + Send + Sync {
fn name(&self) -> &str;
/// Returns the user-defined display name of the UDF given the arguments
- ///
fn display_name(&self, args: &[Expr]) -> Result<String> {
- let names: Vec<String> =
args.iter().map(create_name).collect::<Result<_>>()?;
+ let names: Vec<String> =
args.iter().map(ToString::to_string).collect();
+ // TODO: join with ", " to standardize the formatting of Vec<Expr>,
<https://github.com/apache/datafusion/issues/10364>
Ok(format!("{}({})", self.name(), names.join(",")))
}
+ /// Returns the user-defined schema name of the UDF given the arguments
Review Comment:
```suggestion
/// Returns the name of the column this expression would create
///
/// See [`Expr::schema_name`] for details
```
Maybe it is also worth doing the `impl Display` thing here too which would
allow avoiding these string allocations
##########
datafusion/expr/src/expr.rs:
##########
@@ -983,10 +983,290 @@ impl PartialOrd for Expr {
}
impl Expr {
- /// Returns the name of this expression as it should appear in a schema.
This name
- /// will not include any CAST expressions.
- pub fn display_name(&self) -> Result<String> {
- create_name(self)
+ /// Returns the name for schema / field that is different from Display
+ /// Most of the expressions are the same as Display
+ /// Those are the main difference
+ /// 1. Alias, where excludes expression
+ /// 2. Cast / TryCast, where takes expression only
Review Comment:
Here is a suggesiton for how to improve this documentation:
```suggestion
/// The name of the column (field) that this `Expr` will produce.
///
/// For example, for a projection (e.g. `SELECT <expr>`) the resulting
arrow
/// [`Schema`] will have a field with this name.
///
/// Note that the resulting string is subtlety different than the
`Display`
/// representation for certain `Expr`. Some differences:
///
/// 1. [`Expr::Alias`], which shows only the alias itself
/// 2. [`Expr::Cast`] / [`Expr::TryCast`], which only displays the
expression
///
/// # Example
/// ```
/// # use datafusion_expr::{col, lit};
/// let expr = col("foo").eq(lit(42));
/// assert_eq!("foo = Int32(42)", expr.schema_name().unwrap());
///
/// let expr = col("foo").alias("bar").eq(lit(11));
/// assert_eq!("bar = Int32(11)", expr.schema_name().unwrap());
/// ```
///
/// [`Schema`]: arrow::datatypes::Schema
```
##########
datafusion/expr/src/expr.rs:
##########
@@ -983,10 +983,290 @@ impl PartialOrd for Expr {
}
impl Expr {
- /// Returns the name of this expression as it should appear in a schema.
This name
- /// will not include any CAST expressions.
- pub fn display_name(&self) -> Result<String> {
- create_name(self)
+ /// Returns the name for schema / field that is different from Display
+ /// Most of the expressions are the same as Display
+ /// Those are the main difference
+ /// 1. Alias, where excludes expression
+ /// 2. Cast / TryCast, where takes expression only
+ pub fn schema_name(&self) -> Result<String> {
Review Comment:
If we are going to introduce a new API anyways, what do you think about
making an API that doesn't *require* allocating a new string and making it
infallable. Something like
```suggestion
pub fn schema_name<'a>(&'a self) -> impl Display + 'a {
```
We could probably then implement a new type thing and mostly use the same
code:
```rust
// new type wrapper
struct SchemaDisplay<'a>(&'a Expr);
impl <'a> Display for SchemaDisplay<'a> {
fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
match self {
// The same as Display
Expr::Column(_)
| Expr::Literal(_)
| Expr::ScalarVariable(..)
| Expr::Sort(_)
| Expr::OuterReferenceColumn(..)
| Expr::Placeholder(_)
| Expr::Wildcard { .. } => write!(f, "{self}")?,
...
}
}
return SchemaDisplay(self)
```
The benefit of doing this would be anywhere it needed to get formatted would
not require a copy
```rust
println!("This would not allocated a String: {}", expr.schema_name());
```
```rust
// get schema name as a string:
let schema_name = expr.schema_name().to_string();
##########
datafusion/substrait/tests/cases/consumer_integration.rs:
##########
@@ -358,8 +358,8 @@ mod tests {
let plan = from_substrait_plan(&ctx, &proto).await?;
let plan_str = format!("{:?}", plan);
- assert_eq!(plan_str, "Projection: Decimal128(Some(10000),5,2) *
sum(CASE WHEN FILENAME_PLACEHOLDER_1.p_type LIKE CAST(Utf8(\"PROMO%\") AS Utf8)
THEN FILENAME_PLACEHOLDER_0.l_extendedprice * Int32(1) -
FILENAME_PLACEHOLDER_0.l_discount ELSE Decimal128(Some(0),19,0) END) /
sum(FILENAME_PLACEHOLDER_0.l_extendedprice * Int32(1) -
FILENAME_PLACEHOLDER_0.l_discount) AS PROMO_REVENUE\
- \n Aggregate: groupBy=[[]], aggr=[[sum(CASE WHEN
FILENAME_PLACEHOLDER_1.p_type LIKE CAST(Utf8(\"PROMO%\") AS Utf8) THEN
FILENAME_PLACEHOLDER_0.l_extendedprice * Int32(1) -
FILENAME_PLACEHOLDER_0.l_discount ELSE Decimal128(Some(0),19,0) END),
sum(FILENAME_PLACEHOLDER_0.l_extendedprice * Int32(1) -
FILENAME_PLACEHOLDER_0.l_discount)]]\
+ assert_eq!(plan_str, "Projection: Decimal128(Some(10000),5,2) *
sum(CASE WHEN FILENAME_PLACEHOLDER_1.p_type LIKE Utf8(\"PROMO%\") THEN
FILENAME_PLACEHOLDER_0.l_extendedprice * Int32(1) -
FILENAME_PLACEHOLDER_0.l_discount ELSE Decimal128(Some(0),19,0) END) /
sum(FILENAME_PLACEHOLDER_0.l_extendedprice * Int32(1) -
FILENAME_PLACEHOLDER_0.l_discount) AS PROMO_REVENUE\
Review Comment:
I think it makes sense as long as the cast is still in plans (which it is)
##########
datafusion/expr/src/expr.rs:
##########
@@ -983,10 +983,290 @@ impl PartialOrd for Expr {
}
impl Expr {
- /// Returns the name of this expression as it should appear in a schema.
This name
Review Comment:
Since this is a pub function what do you think about leaving it in marked as
deprecated to help migration?
I think this make the PR much easier to handle
Something like
```rust
#[deprecated(since = "31.0.0", note = "use data_type instead")]
pub fn display_name(&self) -> Result<String> {
self.schema_name()
}
```
##########
datafusion/sqllogictest/test_files/array.slt:
##########
@@ -1137,7 +1137,7 @@ from arrays_values_without_nulls;
## array_element (aliases: array_extract, list_extract, list_element)
# Testing with empty arguments should result in an error
-query error DataFusion error: Error during planning: Error during planning:
array_element does not support zero arguments.
+query error DataFusion error: Execution error: expect 2 args, got 0
Review Comment:
the old error message was nicer -- maybe we can update the code that
generates this message to be nicer too 🤔
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