add missing file

Author: adriangb

datafusion/functions-aggregate/src/utils.rs

@@ -0,0 +1,74 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+use std::sync::Arc;
+
+use arrow::array::RecordBatch;
+use arrow::datatypes::Schema;
+use datafusion_common::{internal_err, plan_err, DataFusionError, Result, ScalarValue};
+use datafusion_expr::ColumnarValue;
+use datafusion_physical_expr_common::physical_expr::PhysicalExpr;
+
+/// Evaluates a physical expression to extract its scalar value.
+///
+/// This is used to extract constant values from expressions (like percentile parameters)
+/// by evaluating them against an empty record batch.
+pub(crate) fn get_percentile_scalar_value(
+    expr: &Arc<dyn PhysicalExpr>,
+) -> Result<ScalarValue> {
+    let empty_schema = Arc::new(Schema::empty());
+    let batch = RecordBatch::new_empty(Arc::clone(&empty_schema));
+    if let ColumnarValue::Scalar(s) = expr.evaluate(&batch)? {
+        Ok(s)
+    } else {
+        internal_err!("Didn't expect ColumnarValue::Array")
+    }
+}
+
+/// Validates that a percentile expression is a literal float value between 0.0 and 1.0.
+///
+/// Used by both `percentile_cont` and `approx_percentile_cont` to validate their
+/// percentile parameters.
+pub(crate) fn validate_percentile_expr(
+    expr: &Arc<dyn PhysicalExpr>,
+    fn_name: &str,
+) -> Result<f64> {
+    let scalar_value = get_percentile_scalar_value(expr).map_err(|_e| {
+        DataFusionError::Plan(format!(
+            "Percentile value for '{fn_name}' must be a literal"
+        ))
+    })?;
+
+    let percentile = match scalar_value {
+        ScalarValue::Float32(Some(value)) => value as f64,
+        ScalarValue::Float64(Some(value)) => value,
+        sv => {
+            return plan_err!(
+                "Percentile value for '{fn_name}' must be Float32 or Float64 literal (got data type {})",
+                sv.data_type()
+            )
+        }
+    };
+
+    // Ensure the percentile is between 0 and 1.
+    if !(0.0..=1.0).contains(&percentile) {
+        return plan_err!(
+            "Percentile value must be between 0.0 and 1.0 inclusive, {percentile} is invalid"
+        );
+    }
+    Ok(percentile)
+}