alamb commented on code in PR #10268:
URL: https://github.com/apache/datafusion/pull/10268#discussion_r1586698773
##########
datafusion/expr/src/type_coercion/functions.rs:
##########
@@ -53,20 +54,31 @@ pub fn data_types(
}
}
- let valid_types = get_valid_types(&signature.type_signature,
current_types)?;
-
+ let mut valid_types = get_valid_types(&signature.type_signature,
current_types)?;
if valid_types
.iter()
.any(|data_type| data_type == current_types)
{
return Ok(current_types.to_vec());
}
- // Try and coerce the argument types to match the signature, returning the
- // coerced types from the first matching signature.
- for valid_types in valid_types {
- if let Some(types) = maybe_data_types(&valid_types, current_types) {
- return Ok(types);
+ // Well-supported signature that returns exact valid types.
+ if !valid_types.is_empty()
+ && matches!(signature.type_signature,
TypeSignature::VariadicEqualOrNull)
+ {
+ // exact valid types
+ assert_eq!(valid_types.len(), 1);
+ let valid_types = valid_types.swap_remove(0);
Review Comment:
is it a problem that this may change the type ordering? So that the last
type is now the first in the new Vec?
##########
datafusion/functions/src/core/coalesce.rs:
##########
@@ -60,9 +59,8 @@ impl ScalarUDFImpl for CoalesceFunc {
}
fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
- // COALESCE has multiple args and they might get coerced, get a
preview of this
Review Comment:
👍 ❤️
##########
datafusion/sqllogictest/test_files/functions.slt:
##########
@@ -1158,3 +1158,347 @@ drop table uuid_table
statement ok
drop table t
+
+
+# Test coalesce function
+query I
+select coalesce(1, 2, 3);
+----
+1
+
+# test with first null
+query ?T
+select coalesce(null, 3, 2, 1), arrow_typeof(coalesce(null, 3, 2, 1));
+----
+3 Int64
+
+# test with null values
+query ?
+select coalesce(null, null);
+----
+NULL
+
+# cast to float
+query IT
+select
+ coalesce(1, 2.0),
+ arrow_typeof(coalesce(1, 2.0))
+;
+----
+1 Float64
+
+query RT
+select
+ coalesce(2.0, 1),
+ arrow_typeof(coalesce(2.0, 1))
+;
+----
+2 Float64
+
+query IT
+select
+ coalesce(1, arrow_cast(2.0, 'Float32')),
+ arrow_typeof(coalesce(1, arrow_cast(2.0, 'Float32')))
+;
+----
+1 Float32
+
+# test with empty args
+query error
+select coalesce();
+
+# test with different types
+query I
+select coalesce(arrow_cast(1, 'Int32'), arrow_cast(1, 'Int64'));
+----
+1
+
+# test with nulls
+query ?T
+select coalesce(null, null, null), arrow_typeof(coalesce(null, null));
+----
+NULL Null
+
+# i32 and u32, cast to wider type i64
+query IT
+select
+ coalesce(arrow_cast(2, 'Int32'), arrow_cast(3, 'UInt32')),
+ arrow_typeof(coalesce(arrow_cast(2, 'Int32'), arrow_cast(3, 'UInt32')));
+----
+2 Int64
+
+query IT
+select
+ coalesce(arrow_cast(2, 'Int16'), arrow_cast(3, 'UInt16')),
+ arrow_typeof(coalesce(arrow_cast(2, 'Int16'), arrow_cast(3, 'UInt16')));
+----
+2 Int32
+
+query IT
+select
+ coalesce(arrow_cast(2, 'Int8'), arrow_cast(3, 'UInt8')),
+ arrow_typeof(coalesce(arrow_cast(2, 'Int8'), arrow_cast(3, 'UInt8')));
+----
+2 Int16
+
+# i64 and u32, cast to wider type i64
+query IT
+select
+ coalesce(2, arrow_cast(3, 'UInt32')),
+ arrow_typeof(coalesce(2, arrow_cast(3, 'UInt32')));
+----
+2 Int64
+
+# TODO: Got types (i64, u64), casting to decimal or double or even i128 if
supported
+query IT
+select
+ coalesce(2, arrow_cast(3, 'UInt64')),
+ arrow_typeof(coalesce(2, arrow_cast(3, 'UInt64')));
+----
+2 Int64
+
+statement ok
+create table t1 (a bigint, b int, c int) as values (null, null, 1), (null, 2,
null);
+
+# Follow Postgres and DuckDB behavior, since a is bigint, although the value
is null, all args are coerced to bigint
+query IT
+select
+ coalesce(a, b, c),
+ arrow_typeof(coalesce(a, b, c))
+from t1;
+----
+1 Int64
+2 Int64
+
+# b, c has the same type int, so the result is int
+query IT
+select
+ coalesce(b, c),
+ arrow_typeof(coalesce(b, c))
+from t1;
+----
+1 Int32
+2 Int32
+
+statement ok
+drop table t1;
+
+# test multi rows
+statement ok
+CREATE TABLE t1(
+ c1 int,
+ c2 int
+) as VALUES
+(1, 2),
+(NULL, 2),
+(1, NULL),
+(NULL, NULL);
+
+query I
+SELECT COALESCE(c1, c2) FROM t1
+----
+1
+2
+1
+NULL
+
+statement ok
+drop table t1;
+
+# Decimal128(7, 2) and int64 are coerced to common wider type Decimal128(22, 2)
+query RT
+select
+ coalesce(arrow_cast(2, 'Decimal128(7, 2)'), 0),
+ arrow_typeof(coalesce(arrow_cast(2, 'Decimal128(7, 2)'), 0))
+----
+2 Decimal128(22, 2)
+
+query RT
+select
+ coalesce(arrow_cast(2, 'Decimal256(7, 2)'), 0),
+ arrow_typeof(coalesce(arrow_cast(2, 'Decimal256(7, 2)'), 0));
+----
+2 Decimal256(22, 2)
+
+# coalesce string
+query T?
+select
+ coalesce('', 'test'),
+ coalesce(null, 'test');
+----
+(empty) test
+
+# coalesce utf8 and large utf8
+query TT
+select
+ coalesce('a', arrow_cast('b', 'LargeUtf8')),
+ arrow_typeof(coalesce('a', arrow_cast('b', 'LargeUtf8')))
+;
+----
+a LargeUtf8
+
+# coalesce array
+query ?T
+select
+ coalesce(array[1, 2], array[3, 4]),
+ arrow_typeof(coalesce(array[1, 2], array[3, 4]));
+----
+[1, 2] List(Field { name: "item", data_type: Int64, nullable: true, dict_id:
0, dict_is_ordered: false, metadata: {} })
+
+query ?T
+select
+ coalesce(null, array[3, 4]),
+ arrow_typeof(coalesce(array[1, 2], array[3, 4]));
+----
+[3, 4] List(Field { name: "item", data_type: Int64, nullable: true, dict_id:
0, dict_is_ordered: false, metadata: {} })
+
+# TODO: after switch signature of array to the same with coalesce, this query
should be fixed
+query error
+select
+ coalesce(array[1, 2], array[arrow_cast(3, 'Int32'), arrow_cast(4, 'Int32')]),
+ arrow_typeof(coalesce(array[1, 2], array[arrow_cast(3, 'Int32'),
arrow_cast(4, 'Int32')]));
+
+statement ok
+create table test1 as values (arrow_cast('foo', 'Dictionary(Int32, Utf8)')),
(null);
+
+# Dictionary and String are not coercible
Review Comment:
This query actually works on main so making it error seems like a regression
to me
```sql
DataFusion CLI v37.1.0
> create table test1 as values (arrow_cast('foo', 'Dictionary(Int32,
Utf8)')), (null);
0 row(s) fetched.
Elapsed 0.011 seconds.
> select coalesce(column1, 'none_set') from test1;
+------------------------------------------+
| coalesce(test1.column1,Utf8("none_set")) |
+------------------------------------------+
| foo |
| none_set |
+------------------------------------------+
2 row(s) fetched.
Elapsed 0.003 seconds.
> select coalesce(null, column1, 'none_set') from test1;
+-----------------------------------------------+
| coalesce(NULL,test1.column1,Utf8("none_set")) |
+-----------------------------------------------+
| foo |
| none_set |
+-----------------------------------------------+
2 row(s) fetched.
Elapsed 0.002 seconds.
```
##########
datafusion/expr/src/signature.rs:
##########
@@ -92,14 +92,22 @@ pub enum TypeSignature {
/// A function such as `concat` is `Variadic(vec![DataType::Utf8,
DataType::LargeUtf8])`
Variadic(Vec<DataType>),
/// One or more arguments of an arbitrary but equal type.
- /// DataFusion attempts to coerce all argument types to match the first
argument's type
+ /// DataFusion attempts to coerce all argument types to match to the
common type with comparision coercion.
Review Comment:
Can we please link to
https://docs.rs/datafusion/latest/datafusion/logical_expr/type_coercion/binary/fn.comparison_coercion.html
that explains (however limited) what comparison coercion is?
##########
datafusion/expr/src/type_coercion/binary.rs:
##########
@@ -289,15 +290,169 @@ fn bitwise_coercion(left_type: &DataType, right_type:
&DataType) -> Option<DataT
}
}
+#[derive(Debug, PartialEq, Eq, Hash, Clone)]
+enum TypeCategory {
+ Array,
+ Boolean,
+ Numeric,
+ // String, well-defined type, but are considered as unknown type.
+ DateTime,
+ Composite,
+ Unknown,
+ NotSupported,
+}
+
+fn data_type_category(data_type: &DataType) -> TypeCategory {
Review Comment:
This could also be something like
```rust
impl From<&DataType> for TypeCategory {
...
```
And then you create a `TypeCategory` like
```rust
let category = TypeCategory::from(&type)
```
##########
datafusion/expr/src/signature.rs:
##########
@@ -92,14 +92,22 @@ pub enum TypeSignature {
/// A function such as `concat` is `Variadic(vec![DataType::Utf8,
DataType::LargeUtf8])`
Variadic(Vec<DataType>),
/// One or more arguments of an arbitrary but equal type.
- /// DataFusion attempts to coerce all argument types to match the first
argument's type
+ /// DataFusion attempts to coerce all argument types to match to the
common type with comparision coercion.
///
/// # Examples
/// Given types in signature should be coercible to the same final type.
/// A function such as `make_array` is `VariadicEqual`.
///
/// `make_array(i32, i64) -> make_array(i64, i64)`
VariadicEqual,
+ /// One or more arguments of an arbitrary but equal type or Null.
+ /// Non-comparison coercion is attempted to match the signatures.
+ ///
+ /// Functions like `coalesce` is `VariadicEqual`.
+ // TODO: Temporary Signature, to differentiate existing VariadicEqual.
+ // After we swtich `make_array` to VariadicEqualOrNull,
+ // we can reuse VariadicEqual.
+ VariadicEqualOrNull,
Review Comment:
Maybe we could do something like this (basically to flavor the type
signature) 🤔
```rust
pub enum TypeSignature {
...
/// Rather than the usual coercion rules, special type union rules are
applied
Union(Box<TypeSignature>)
}
```
##########
datafusion/expr/src/type_coercion/functions.rs:
##########
@@ -293,6 +314,32 @@ fn maybe_data_types(
Some(new_type)
}
+/// Check if the current argument types can be coerced to match the given
`valid_types`
+/// unlike `maybe_data_types`, this function does not coerce the types.
Review Comment:
this comment says "function does not coerce the types" but then it permits
types in `can_cast_types`. I may be misunderstanding what coerce means in this
case
##########
datafusion/expr/src/type_coercion/functions.rs:
##########
@@ -450,19 +473,7 @@ fn coerced_from<'a>(
{
Some(type_into.clone())
}
- // More coerce rules.
- // Note that not all rules in `comparison_coercion` can be reused here.
- // For example, all numeric types can be coerced into Utf8 for
comparison,
- // but not for function arguments.
- _ => comparison_binary_numeric_coercion(type_into, type_from).and_then(
Review Comment:
cc @viirya
##########
datafusion/expr/src/signature.rs:
##########
@@ -92,14 +92,22 @@ pub enum TypeSignature {
/// A function such as `concat` is `Variadic(vec![DataType::Utf8,
DataType::LargeUtf8])`
Variadic(Vec<DataType>),
/// One or more arguments of an arbitrary but equal type.
- /// DataFusion attempts to coerce all argument types to match the first
argument's type
+ /// DataFusion attempts to coerce all argument types to match to the
common type with comparision coercion.
///
/// # Examples
/// Given types in signature should be coercible to the same final type.
/// A function such as `make_array` is `VariadicEqual`.
///
/// `make_array(i32, i64) -> make_array(i64, i64)`
VariadicEqual,
+ /// One or more arguments of an arbitrary but equal type or Null.
+ /// Non-comparison coercion is attempted to match the signatures.
+ ///
+ /// Functions like `coalesce` is `VariadicEqual`.
Review Comment:
I am a little confused about what "Non-comparison coercion" means in this
situation. Specifically how comparison coercion and non comparision coercion
differ 🤔
Does non comparison coercion mean "type union resolution" (aka
`type_union_resolution`)?
Also, I think `coalesce` is now `VariadicEqualOrNull` (this says the
opposite)
```suggestion
/// One or more arguments of an arbitrary but equal type or Null.
/// Non-comparison coercion is attempted to match the signatures.
///
/// Functions like `coalesce` is `VariadicEqualOrNull`.
```
##########
datafusion/sqllogictest/test_files/functions.slt:
##########
@@ -1158,3 +1158,347 @@ drop table uuid_table
statement ok
drop table t
+
+
+# Test coalesce function
+query I
+select coalesce(1, 2, 3);
+----
+1
+
+# test with first null
+query ?T
+select coalesce(null, 3, 2, 1), arrow_typeof(coalesce(null, 3, 2, 1));
+----
+3 Int64
+
+# test with null values
+query ?
+select coalesce(null, null);
+----
+NULL
+
+# cast to float
+query IT
+select
+ coalesce(1, 2.0),
+ arrow_typeof(coalesce(1, 2.0))
+;
+----
+1 Float64
+
+query RT
+select
+ coalesce(2.0, 1),
+ arrow_typeof(coalesce(2.0, 1))
+;
+----
+2 Float64
+
+query IT
+select
+ coalesce(1, arrow_cast(2.0, 'Float32')),
+ arrow_typeof(coalesce(1, arrow_cast(2.0, 'Float32')))
+;
+----
+1 Float32
+
+# test with empty args
+query error
+select coalesce();
+
+# test with different types
+query I
+select coalesce(arrow_cast(1, 'Int32'), arrow_cast(1, 'Int64'));
+----
+1
+
+# test with nulls
+query ?T
+select coalesce(null, null, null), arrow_typeof(coalesce(null, null));
+----
+NULL Null
+
+# i32 and u32, cast to wider type i64
+query IT
+select
+ coalesce(arrow_cast(2, 'Int32'), arrow_cast(3, 'UInt32')),
+ arrow_typeof(coalesce(arrow_cast(2, 'Int32'), arrow_cast(3, 'UInt32')));
+----
+2 Int64
+
+query IT
+select
+ coalesce(arrow_cast(2, 'Int16'), arrow_cast(3, 'UInt16')),
+ arrow_typeof(coalesce(arrow_cast(2, 'Int16'), arrow_cast(3, 'UInt16')));
+----
+2 Int32
+
+query IT
+select
+ coalesce(arrow_cast(2, 'Int8'), arrow_cast(3, 'UInt8')),
+ arrow_typeof(coalesce(arrow_cast(2, 'Int8'), arrow_cast(3, 'UInt8')));
+----
+2 Int16
+
+# i64 and u32, cast to wider type i64
+query IT
+select
+ coalesce(2, arrow_cast(3, 'UInt32')),
+ arrow_typeof(coalesce(2, arrow_cast(3, 'UInt32')));
+----
+2 Int64
+
+# TODO: Got types (i64, u64), casting to decimal or double or even i128 if
supported
+query IT
+select
+ coalesce(2, arrow_cast(3, 'UInt64')),
+ arrow_typeof(coalesce(2, arrow_cast(3, 'UInt64')));
+----
+2 Int64
+
+statement ok
+create table t1 (a bigint, b int, c int) as values (null, null, 1), (null, 2,
null);
+
+# Follow Postgres and DuckDB behavior, since a is bigint, although the value
is null, all args are coerced to bigint
+query IT
+select
+ coalesce(a, b, c),
+ arrow_typeof(coalesce(a, b, c))
+from t1;
+----
+1 Int64
+2 Int64
+
+# b, c has the same type int, so the result is int
+query IT
+select
+ coalesce(b, c),
+ arrow_typeof(coalesce(b, c))
+from t1;
+----
+1 Int32
+2 Int32
+
+statement ok
+drop table t1;
+
+# test multi rows
+statement ok
+CREATE TABLE t1(
+ c1 int,
+ c2 int
+) as VALUES
+(1, 2),
+(NULL, 2),
+(1, NULL),
+(NULL, NULL);
+
+query I
+SELECT COALESCE(c1, c2) FROM t1
+----
+1
+2
+1
+NULL
+
+statement ok
+drop table t1;
+
+# Decimal128(7, 2) and int64 are coerced to common wider type Decimal128(22, 2)
+query RT
+select
+ coalesce(arrow_cast(2, 'Decimal128(7, 2)'), 0),
+ arrow_typeof(coalesce(arrow_cast(2, 'Decimal128(7, 2)'), 0))
+----
+2 Decimal128(22, 2)
+
+query RT
+select
+ coalesce(arrow_cast(2, 'Decimal256(7, 2)'), 0),
+ arrow_typeof(coalesce(arrow_cast(2, 'Decimal256(7, 2)'), 0));
+----
+2 Decimal256(22, 2)
+
+# coalesce string
+query T?
+select
+ coalesce('', 'test'),
+ coalesce(null, 'test');
+----
+(empty) test
+
+# coalesce utf8 and large utf8
+query TT
+select
+ coalesce('a', arrow_cast('b', 'LargeUtf8')),
+ arrow_typeof(coalesce('a', arrow_cast('b', 'LargeUtf8')))
+;
+----
+a LargeUtf8
+
+# coalesce array
+query ?T
+select
+ coalesce(array[1, 2], array[3, 4]),
+ arrow_typeof(coalesce(array[1, 2], array[3, 4]));
+----
+[1, 2] List(Field { name: "item", data_type: Int64, nullable: true, dict_id:
0, dict_is_ordered: false, metadata: {} })
+
+query ?T
+select
+ coalesce(null, array[3, 4]),
+ arrow_typeof(coalesce(array[1, 2], array[3, 4]));
+----
+[3, 4] List(Field { name: "item", data_type: Int64, nullable: true, dict_id:
0, dict_is_ordered: false, metadata: {} })
+
+# TODO: after switch signature of array to the same with coalesce, this query
should be fixed
+query error
+select
+ coalesce(array[1, 2], array[arrow_cast(3, 'Int32'), arrow_cast(4, 'Int32')]),
+ arrow_typeof(coalesce(array[1, 2], array[arrow_cast(3, 'Int32'),
arrow_cast(4, 'Int32')]));
+
+statement ok
+create table test1 as values (arrow_cast('foo', 'Dictionary(Int32, Utf8)')),
(null);
+
+# Dictionary and String are not coercible
+query error
+select coalesce(column1, 'none_set') from test1;
+
+query error
+select coalesce(null, column1, 'none_set') from test1;
+
+# explicitly cast to Utf8
+query T
+select coalesce(arrow_cast(column1, 'Utf8'), 'none_set') from test1;
+----
+foo
+none_set
+
+statement ok
+drop table test1
+
+# Numeric and Dictionary are not coercible
Review Comment:
Likewise, this also works on main:
```
> select coalesce(34, arrow_cast(123, 'Dictionary(Int32, Int8)'));
+----------------------------------------------------------------------------+
| coalesce(Int64(34),arrow_cast(Int64(123),Utf8("Dictionary(Int32, Int8)")))
|
+----------------------------------------------------------------------------+
| 34
|
+----------------------------------------------------------------------------+
1 row(s) fetched.
Elapsed 0.001 seconds.
```
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