fix: coalesce schema issues

datafusion/core/src/dataframe/mod.rs

@@ -2029,6 +2029,43 @@ mod tests {
         Ok(())
     }
 
+    #[tokio::test]
+    async fn test_coalesce_schema() -> Result<()> {
+        let ctx = SessionContext::new();
+
+        let query = r#"SELECT COALESCE(null, 5)"#;
+
+        let result = ctx.sql(query).await?;
+        assert_logical_expr_schema_eq_physical_expr_schema(result).await?;
+        Ok(())
+    }
+
+    #[tokio::test]
+    async fn test_coalesce_from_values_schema() -> Result<()> {
+        let ctx = SessionContext::new();
+
+        let query = r#"SELECT COALESCE(column1, column2) FROM VALUES (null, 1.2)"#;
+
+        let result = ctx.sql(query).await?;
+        assert_logical_expr_schema_eq_physical_expr_schema(result).await?;
+        Ok(())
+    }
+
+    #[tokio::test]
+    async fn test_coalesce_from_values_schema_multiple_rows() -> Result<()> {
+        let ctx = SessionContext::new();
+
+        let query = r#"SELECT COALESCE(column1, column2)
+        FROM VALUES
+        (null, 1.2),
+        (1.1, null),
+        (2, 5);"#;
+
+        let result = ctx.sql(query).await?;
+        assert_logical_expr_schema_eq_physical_expr_schema(result).await?;
+        Ok(())
+    }
+
     #[tokio::test]
     async fn test_array_agg_schema() -> Result<()> {
         let ctx = SessionContext::new();

datafusion/expr/src/expr_schema.rs

@@ -151,21 +151,22 @@ impl ExprSchemable for Expr {
                     .collect::<Result<Vec<_>>>()?;
 
                 // verify that function is invoked with correct number and type of arguments as defined in `TypeSignature`
-                data_types_with_scalar_udf(&arg_data_types, func).map_err(|err| {
-                    plan_datafusion_err!(
-                        "{} {}",
-                        err,
-                        utils::generate_signature_error_msg(
-                            func.name(),
-                            func.signature().clone(),
-                            &arg_data_types,
+                let new_data_types = data_types_with_scalar_udf(&arg_data_types, func)
+                    .map_err(|err| {
+                        plan_datafusion_err!(
+                            "{} {}",
+                            err,
+                            utils::generate_signature_error_msg(
+                                func.name(),
+                                func.signature().clone(),
+                                &arg_data_types,
+                            )
                         )
-                    )
-                })?;
+                    })?;
 
                 // perform additional function arguments validation (due to limited
                 // expressiveness of `TypeSignature`), then infer return type
-                Ok(func.return_type_from_exprs(args, schema, &arg_data_types)?)
+                Ok(func.return_type_from_exprs(args, schema, &new_data_types)?)
             }
             Expr::WindowFunction(window_function) => self
                 .data_type_and_nullable_with_window_function(schema, window_function)

datafusion/expr/src/logical_plan/builder.rs

@@ -216,7 +216,9 @@ impl LogicalPlanBuilder {
                     common_type = Some(data_type);
                 }
             }
-            field_types.push(common_type.unwrap_or(DataType::Utf8));
+            // assuming common_type was not set, and no error, therefore the type should be NULL
+            // since the code loop skips NULL
+            field_types.push(common_type.unwrap_or(DataType::Null));
         }
         // wrap cast if data type is not same as common type.
         for row in &mut values {

datafusion/functions/src/core/coalesce.rs

@@ -21,11 +21,11 @@ use arrow::array::{new_null_array, BooleanArray};
 use arrow::compute::kernels::zip::zip;
 use arrow::compute::{and, is_not_null, is_null};
 use arrow::datatypes::DataType;
-
 use datafusion_common::{exec_err, ExprSchema, Result};
 use datafusion_expr::type_coercion::binary::type_union_resolution;
 use datafusion_expr::{ColumnarValue, Expr, ExprSchemable};
 use datafusion_expr::{ScalarUDFImpl, Signature, Volatility};
+use itertools::Itertools;
 
 #[derive(Debug)]
 pub struct CoalesceFunc {
@@ -60,12 +60,16 @@ impl ScalarUDFImpl for CoalesceFunc {
     }
 
     fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
-        Ok(arg_types[0].clone())
+        Ok(arg_types
+            .iter()
+            .find_or_first(|d| !d.is_null())
+            .unwrap()
+            .clone())
     }
 
-    // If all the element in coalesce is non-null, the result is non-null
+    // If any the arguments in coalesce is non-null, the result is non-null
     fn is_nullable(&self, args: &[Expr], schema: &dyn ExprSchema) -> bool {
-        args.iter().any(|e| e.nullable(schema).ok().unwrap_or(true))
+        args.iter().all(|e| e.nullable(schema).ok().unwrap_or(true))
     }
 
     /// coalesce evaluates to the first value which is not NULL
@@ -154,4 +158,22 @@ mod test {
             .unwrap();
         assert_eq!(return_type, DataType::Date32);
     }
+
+    #[test]
+    fn test_coalesce_return_types_with_nulls_first() {
+        let coalesce = core::coalesce::CoalesceFunc::new();
+        let return_type = coalesce
+            .return_type(&[DataType::Null, DataType::Date32])
+            .unwrap();
+        assert_eq!(return_type, DataType::Date32);
+    }
+
+    #[test]
+    fn test_coalesce_return_types_with_nulls_last() {
+        let coalesce = core::coalesce::CoalesceFunc::new();
+        let return_type = coalesce
+            .return_type(&[DataType::Int64, DataType::Null])
+            .unwrap();
+        assert_eq!(return_type, DataType::Int64);
+    }
 }

datafusion/functions/src/datetime/to_local_time.rs

@@ -22,22 +22,16 @@ use std::sync::Arc;
 use arrow::array::timezone::Tz;
 use arrow::array::{Array, ArrayRef, PrimitiveBuilder};
 use arrow::datatypes::DataType::Timestamp;
+use arrow::datatypes::TimeUnit::{Microsecond, Millisecond, Nanosecond, Second};
 use arrow::datatypes::{
     ArrowTimestampType, DataType, TimestampMicrosecondType, TimestampMillisecondType,
     TimestampNanosecondType, TimestampSecondType,
 };
-use arrow::datatypes::{
-    TimeUnit,
-    TimeUnit::{Microsecond, Millisecond, Nanosecond, Second},
-};
 
 use chrono::{DateTime, MappedLocalTime, Offset, TimeDelta, TimeZone, Utc};
 use datafusion_common::cast::as_primitive_array;
-use datafusion_common::{exec_err, DataFusionError, Result, ScalarValue};
-use datafusion_expr::TypeSignature::Exact;
-use datafusion_expr::{
-    ColumnarValue, ScalarUDFImpl, Signature, Volatility, TIMEZONE_WILDCARD,
-};
+use datafusion_common::{exec_err, plan_err, DataFusionError, Result, ScalarValue};
+use datafusion_expr::{ColumnarValue, ScalarUDFImpl, Signature, Volatility};
 
 /// A UDF function that converts a timezone-aware timestamp to local time (with no offset or
 /// timezone information). In other words, this function strips off the timezone from the timestamp,
@@ -55,20 +49,8 @@ impl Default for ToLocalTimeFunc {
 
 impl ToLocalTimeFunc {
     pub fn new() -> Self {
-        let base_sig = |array_type: TimeUnit| {
-            [
-                Exact(vec![Timestamp(array_type, None)]),
-                Exact(vec![Timestamp(array_type, Some(TIMEZONE_WILDCARD.into()))]),
-            ]
-        };
-
-        let full_sig = [Nanosecond, Microsecond, Millisecond, Second]
-            .into_iter()
-            .flat_map(base_sig)
-            .collect::<Vec<_>>();
-
         Self {
-            signature: Signature::one_of(full_sig, Volatility::Immutable),
+            signature: Signature::user_defined(Volatility::Immutable),
         }
     }
 
@@ -328,13 +310,10 @@ impl ScalarUDFImpl for ToLocalTimeFunc {
         }
 
         match &arg_types[0] {
-            Timestamp(Nanosecond, _) => Ok(Timestamp(Nanosecond, None)),
-            Timestamp(Microsecond, _) => Ok(Timestamp(Microsecond, None)),
-            Timestamp(Millisecond, _) => Ok(Timestamp(Millisecond, None)),
-            Timestamp(Second, _) => Ok(Timestamp(Second, None)),
+            Timestamp(timeunit, _) => Ok(Timestamp(*timeunit, None)),
             _ => exec_err!(
                 "The to_local_time function can only accept timestamp as the arg, got {:?}", arg_types[0]
-            ),
+            )
         }
     }
 
@@ -348,6 +327,30 @@ impl ScalarUDFImpl for ToLocalTimeFunc {
 
         self.to_local_time(args)
     }
+
+    fn coerce_types(&self, arg_types: &[DataType]) -> Result<Vec<DataType>> {
+        if arg_types.len() != 1 {
+            return plan_err!(
+                "to_local_time function requires 1 argument, got {:?}",
+                arg_types.len()
+            );
+        }
+
+        let first_arg = arg_types[0].clone();
+        match &first_arg {
+            Timestamp(Nanosecond, timezone) => {
+                Ok(vec![Timestamp(Nanosecond, timezone.clone())])
+            }
+            Timestamp(Microsecond, timezone) => {
+                Ok(vec![Timestamp(Microsecond, timezone.clone())])
+            }
+            Timestamp(Millisecond, timezone) => {
+                Ok(vec![Timestamp(Millisecond, timezone.clone())])
+            }
+            Timestamp(Second, timezone) => Ok(vec![Timestamp(Second, timezone.clone())]),
+            _ => plan_err!("The to_local_time function can only accept Timestamp as the arg got {first_arg}"),
+        }
+    }
 }
 
 #[cfg(test)]

datafusion/functions/src/encoding/inner.rs

@@ -32,7 +32,6 @@ use datafusion_expr::ColumnarValue;
 use std::sync::Arc;
 use std::{fmt, str::FromStr};
 
-use datafusion_expr::TypeSignature::*;
 use datafusion_expr::{ScalarUDFImpl, Signature, Volatility};
 use std::any::Any;
 
@@ -49,17 +48,8 @@ impl Default for EncodeFunc {
 
 impl EncodeFunc {
     pub fn new() -> Self {
-        use DataType::*;
         Self {
-            signature: Signature::one_of(
-                vec![
-                    Exact(vec![Utf8, Utf8]),
-                    Exact(vec![LargeUtf8, Utf8]),
-                    Exact(vec![Binary, Utf8]),
-                    Exact(vec![LargeBinary, Utf8]),
-                ],
-                Volatility::Immutable,
-            ),
+            signature: Signature::user_defined(Volatility::Immutable),
         }
     }
 }
@@ -77,23 +67,39 @@ impl ScalarUDFImpl for EncodeFunc {
     }
 
     fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
-        use DataType::*;
-
-        Ok(match arg_types[0] {
-            Utf8 => Utf8,
-            LargeUtf8 => LargeUtf8,
-            Binary => Utf8,
-            LargeBinary => LargeUtf8,
-            Null => Null,
-            _ => {
-                return plan_err!("The encode function can only accept utf8 or binary.");
-            }
-        })
+        Ok(arg_types[0].to_owned())
     }
 
     fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
         encode(args)
     }
+
+    fn coerce_types(&self, arg_types: &[DataType]) -> Result<Vec<DataType>> {
+        if arg_types.len() != 2 {
+            return plan_err!(
+                "{} expects to get 2 arguments, but got {}",
+                self.name(),
+                arg_types.len()
+            );
+        }
+
+        if arg_types[1] != DataType::Utf8 {
+            return Err(DataFusionError::Plan("2nd argument should be Utf8".into()));
+        }
+
+        match arg_types[0] {
+            DataType::Utf8 | DataType::Binary | DataType::Null => {
+                Ok(vec![DataType::Utf8; 2])
+            }
+            DataType::LargeUtf8 | DataType::LargeBinary => {
+                Ok(vec![DataType::LargeUtf8, DataType::Utf8])
+            }
+            _ => plan_err!(
+                "1st argument should be Utf8 or Binary or Null, got {:?}",
+                arg_types[0]
+            ),
+        }
+    }
 }
 
 #[derive(Debug)]
@@ -109,17 +115,8 @@ impl Default for DecodeFunc {
 
 impl DecodeFunc {
     pub fn new() -> Self {
-        use DataType::*;
         Self {
-            signature: Signature::one_of(
-                vec![
-                    Exact(vec![Utf8, Utf8]),
-                    Exact(vec![LargeUtf8, Utf8]),
-                    Exact(vec![Binary, Utf8]),
-                    Exact(vec![LargeBinary, Utf8]),
-                ],
-                Volatility::Immutable,
-            ),
+            signature: Signature::user_defined(Volatility::Immutable),
         }
     }
 }
@@ -137,23 +134,39 @@ impl ScalarUDFImpl for DecodeFunc {
     }
 
     fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
-        use DataType::*;
-
-        Ok(match arg_types[0] {
-            Utf8 => Binary,
-            LargeUtf8 => LargeBinary,
-            Binary => Binary,
-            LargeBinary => LargeBinary,
-            Null => Null,
-            _ => {
-                return plan_err!("The decode function can only accept utf8 or binary.");
-            }
-        })
+        Ok(arg_types[0].to_owned())
     }
 
     fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
         decode(args)
     }
+
+    fn coerce_types(&self, arg_types: &[DataType]) -> Result<Vec<DataType>> {
+        if arg_types.len() != 2 {
+            return plan_err!(
+                "{} expects to get 2 arguments, but got {}",
+                self.name(),
+                arg_types.len()
+            );
+        }
+
+        if arg_types[1] != DataType::Utf8 {
+            return plan_err!("2nd argument should be Utf8");
+        }
+
+        match arg_types[0] {
+            DataType::Utf8 | DataType::Binary | DataType::Null => {
+                Ok(vec![DataType::Binary, DataType::Utf8])
+            }
+            DataType::LargeUtf8 | DataType::LargeBinary => {
+                Ok(vec![DataType::LargeBinary, DataType::Utf8])
+            }
+            _ => plan_err!(
+                "1st argument should be Utf8 or Binary or Null, got {:?}",
+                arg_types[0]
+            ),
+        }
+    }
 }
 
 #[derive(Debug, Copy, Clone)]