Return scalar result when all inputs are constants in map and make_map

datafusion/common/src/scalar/mod.rs

@@ -2678,7 +2678,10 @@ impl ScalarValue {
             DataType::Duration(TimeUnit::Nanosecond) => {
                 typed_cast!(array, index, DurationNanosecondArray, DurationNanosecond)?
             }
-
+            DataType::Map(_, _) => {
+                let a = array.slice(index, 1);
+                Self::Map(Arc::new(a.as_map().to_owned()))
+            }
             other => {
                 return _not_impl_err!(
                     "Can't create a scalar from array of type \"{other:?}\""

datafusion/functions/src/core/map.rs

@@ -28,7 +28,21 @@ use datafusion_common::{exec_err, internal_err, ScalarValue};
 use datafusion_common::{not_impl_err, Result};
 use datafusion_expr::{ColumnarValue, ScalarUDFImpl, Signature, Volatility};
 
+/// Check if we can evaluate the expr to constant directly.
+///
+/// # Example
+/// ```sql
+/// SELECT make_map('type', 'test') from test
+/// ```
+/// We can evaluate the result of `make_map` directly.
+fn can_evaluate_to_const(args: &[ColumnarValue]) -> bool {
+    args.iter()
+        .all(|arg| matches!(arg, ColumnarValue::Scalar(_)))
+}
+
 fn make_map(args: &[ColumnarValue]) -> Result<ColumnarValue> {
+    let can_evaluate_to_const = can_evaluate_to_const(args);
+
     let (key, value): (Vec<_>, Vec<_>) = args
         .chunks_exact(2)
         .map(|chunk| {
@@ -58,7 +72,7 @@ fn make_map(args: &[ColumnarValue]) -> Result<ColumnarValue> {
         Ok(value) => value,
         Err(e) => return internal_err!("Error concatenating values: {}", e),
     };
-    make_map_batch_internal(key, value)
+    make_map_batch_internal(key, value, can_evaluate_to_const)
 }
 
 fn make_map_batch(args: &[ColumnarValue]) -> Result<ColumnarValue> {
@@ -68,9 +82,12 @@ fn make_map_batch(args: &[ColumnarValue]) -> Result<ColumnarValue> {
             args.len()
         );
     }
+
+    let can_evaluate_to_const = can_evaluate_to_const(args);
+
     let key = get_first_array_ref(&args[0])?;
     let value = get_first_array_ref(&args[1])?;
-    make_map_batch_internal(key, value)
+    make_map_batch_internal(key, value, can_evaluate_to_const)
 }
 
 fn get_first_array_ref(columnar_value: &ColumnarValue) -> Result<ArrayRef> {
@@ -85,7 +102,11 @@ fn get_first_array_ref(columnar_value: &ColumnarValue) -> Result<ArrayRef> {
     }
 }
 
-fn make_map_batch_internal(keys: ArrayRef, values: ArrayRef) -> Result<ColumnarValue> {
+fn make_map_batch_internal(
+    keys: ArrayRef,
+    values: ArrayRef,
+    can_evaluate_to_const: bool,
+) -> Result<ColumnarValue> {
     if keys.null_count() > 0 {
         return exec_err!("map key cannot be null");
     }
@@ -124,8 +145,13 @@ fn make_map_batch_internal(keys: ArrayRef, values: ArrayRef) -> Result<ColumnarV
         .add_buffer(entry_offsets_buffer)
         .add_child_data(entry_struct.to_data())
         .build()?;
+    let map_array = Arc::new(MapArray::from(map_data));
 
-    Ok(ColumnarValue::Array(Arc::new(MapArray::from(map_data))))
+    Ok(if can_evaluate_to_const {
+        ColumnarValue::Scalar(ScalarValue::try_from_array(map_array.as_ref(), 0)?)
+    } else {
+        ColumnarValue::Array(map_array)
+    })
 }
 
 #[derive(Debug)]

datafusion/optimizer/src/simplify_expressions/expr_simplifier.rs

@@ -656,12 +656,35 @@ impl<'a> ConstEvaluator<'a> {
                 } else {
                     // Non-ListArray
                     match ScalarValue::try_from_array(&a, 0) {
-                        Ok(s) => ConstSimplifyResult::Simplified(s),
+                        Ok(s) => {
+                            // TODO: support the optimization for `Map` type after support impl hash for it
+                            if matches!(&s, ScalarValue::Map(_)) {
+                                ConstSimplifyResult::SimplifyRuntimeError(
+                                    DataFusionError::NotImplemented("Const evaluate for Map type is still not supported".to_string()),
+                                    expr,
+                                )
+                            } else {
+                                ConstSimplifyResult::Simplified(s)
+                            }
+                        }
                         Err(err) => ConstSimplifyResult::SimplifyRuntimeError(err, expr),
                     }
                 }
             }
-            ColumnarValue::Scalar(s) => ConstSimplifyResult::Simplified(s),
+            ColumnarValue::Scalar(s) => {
+                // TODO: support the optimization for `Map` type after support impl hash for it
+                if matches!(&s, ScalarValue::Map(_)) {
+                    ConstSimplifyResult::SimplifyRuntimeError(
+                        DataFusionError::NotImplemented(
+                            "Const evaluate for Map type is still not supported"
+                                .to_string(),
+                        ),
+                        expr,
+                    )
+                } else {
+                    ConstSimplifyResult::Simplified(s)
+                }
+            }
         }
     }
 }

datafusion/sqllogictest/test_files/map.slt

@@ -212,3 +212,87 @@ SELECT map(column5, column6) FROM t;
 # {k1:1, k2:2}
 # {k3: 3}
 # {k5: 5}
+
+query ?
+SELECT MAKE_MAP('POST', 41, 'HEAD', 33, 'PATCH', 30, 'OPTION', 29, 'GET', 27, 'PUT', 25, 'DELETE', 24) AS method_count from t;
+----
+{POST: 41, HEAD: 33, PATCH: 30, OPTION: 29, GET: 27, PUT: 25, DELETE: 24}
+{POST: 41, HEAD: 33, PATCH: 30, OPTION: 29, GET: 27, PUT: 25, DELETE: 24}
+{POST: 41, HEAD: 33, PATCH: 30, OPTION: 29, GET: 27, PUT: 25, DELETE: 24}
+
+query I
+SELECT MAKE_MAP('POST', 41, 'HEAD', 33)['POST']  from t;
+----
+41
+41
+41
+
+query ?
+SELECT MAKE_MAP('POST', 41, 'HEAD', 33, 'PATCH', null) from t;
+----
+{POST: 41, HEAD: 33, PATCH: }
+{POST: 41, HEAD: 33, PATCH: }
+{POST: 41, HEAD: 33, PATCH: }
+
+query ?
+SELECT MAKE_MAP('POST', null, 'HEAD', 33, 'PATCH', null) from t;
+----
+{POST: , HEAD: 33, PATCH: }
+{POST: , HEAD: 33, PATCH: }
+{POST: , HEAD: 33, PATCH: }
+
+query ?
+SELECT MAKE_MAP(1, null, 2, 33, 3, null) from t;
+----
+{1: , 2: 33, 3: }
+{1: , 2: 33, 3: }
+{1: , 2: 33, 3: }
+
+query ?
+SELECT MAKE_MAP([1,2], ['a', 'b'], [3,4], ['b']) from t;
+----
+{[1, 2]: [a, b], [3, 4]: [b]}
+{[1, 2]: [a, b], [3, 4]: [b]}
+{[1, 2]: [a, b], [3, 4]: [b]}
+
+query ?
+SELECT MAP(['POST', 'HEAD', 'PATCH'], [41, 33, 30]) from t;
+----
+{POST: 41, HEAD: 33, PATCH: 30}
+{POST: 41, HEAD: 33, PATCH: 30}
+{POST: 41, HEAD: 33, PATCH: 30}
+
+query ?
+SELECT MAP(['POST', 'HEAD', 'PATCH'], [41, 33, null]) from t;
+----
+{POST: 41, HEAD: 33, PATCH: }
+{POST: 41, HEAD: 33, PATCH: }
+{POST: 41, HEAD: 33, PATCH: }
+
+query ?
+SELECT MAP([[1,2], [3,4]], ['a', 'b']) from t;
+----
+{[1, 2]: a, [3, 4]: b}
+{[1, 2]: a, [3, 4]: b}
+{[1, 2]: a, [3, 4]: b}
+
+query ?
+SELECT MAP(make_array('POST', 'HEAD', 'PATCH'), make_array(41, 33, 30)) from t;
+----
+{POST: 41, HEAD: 33, PATCH: 30}
+{POST: 41, HEAD: 33, PATCH: 30}
+{POST: 41, HEAD: 33, PATCH: 30}
+
+query ?
+SELECT MAP(arrow_cast(make_array('POST', 'HEAD', 'PATCH'), 'FixedSizeList(3, Utf8)'), arrow_cast(make_array(41, 33, 30), 'FixedSizeList(3, Int64)'))  from t;
+----
+{POST: 41, HEAD: 33, PATCH: 30}
+{POST: 41, HEAD: 33, PATCH: 30}
+{POST: 41, HEAD: 33, PATCH: 30}
+
+query ?
+SELECT MAP(arrow_cast(make_array('POST', 'HEAD', 'PATCH'), 'LargeList(Utf8)'), arrow_cast(make_array(41, 33, 30), 'LargeList(Int64)')) from t;
+----
+{POST: 41, HEAD: 33, PATCH: 30}
+{POST: 41, HEAD: 33, PATCH: 30}
+{POST: 41, HEAD: 33, PATCH: 30}