liurenjie1024 commented on code in PR #1602:
URL: https://github.com/apache/iceberg-rust/pull/1602#discussion_r2381620650


##########
crates/integrations/datafusion/src/physical_plan/project.rs:
##########
@@ -0,0 +1,494 @@
+// 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.
+
+//! Partition value projection for Iceberg tables.
+
+use std::sync::{Arc, Mutex};
+
+use datafusion::arrow::array::{ArrayRef, RecordBatch, StructArray};
+use datafusion::arrow::datatypes::{DataType, Schema as ArrowSchema};
+use datafusion::common::Result as DFResult;
+use datafusion::error::DataFusionError;
+use datafusion::physical_expr::PhysicalExpr;
+use datafusion::physical_expr::expressions::Column;
+use datafusion::physical_plan::projection::ProjectionExec;
+use datafusion::physical_plan::{ColumnarValue, ExecutionPlan};
+use iceberg::arrow::record_batch_projector::RecordBatchProjector;
+use iceberg::spec::{PartitionSpec, Schema};
+use iceberg::table::Table;
+
+use crate::to_datafusion_error;
+
+/// Column name for the combined partition values struct
+const PARTITION_VALUES_COLUMN: &str = "_partition";
+
+/// Extends an ExecutionPlan with partition value calculations for Iceberg 
tables.
+///
+/// This function takes an input ExecutionPlan and extends it with an 
additional column
+/// containing calculated partition values based on the table's partition 
specification.
+/// For unpartitioned tables, returns the original plan unchanged.
+///
+/// # Arguments
+/// * `input` - The input ExecutionPlan to extend
+/// * `table` - The Iceberg table with partition specification
+///
+/// # Returns
+/// * `Ok(Arc<dyn ExecutionPlan>)` - Extended plan with partition values column
+/// * `Err` - If partition spec is not found or transformation fails
+pub fn project_with_partition(
+    input: Arc<dyn ExecutionPlan>,
+    table: &Table,
+) -> DFResult<Arc<dyn ExecutionPlan>> {
+    let metadata = table.metadata();
+    let partition_spec = metadata.default_partition_spec();
+    let table_schema = metadata.current_schema();
+
+    if partition_spec.is_unpartitioned() {
+        return Ok(input);
+    }
+
+    let input_schema = input.schema();
+    let partition_type = build_partition_type(partition_spec, 
table_schema.as_ref())?;
+    let calculator = PartitionValueCalculator::new(
+        partition_spec.as_ref().clone(),
+        table_schema.as_ref().clone(),
+        partition_type,
+    )?;
+
+    let mut projection_exprs: Vec<(Arc<dyn PhysicalExpr>, String)> =
+        Vec::with_capacity(input_schema.fields().len() + 1);
+
+    for (index, field) in input_schema.fields().iter().enumerate() {
+        let column_expr = Arc::new(Column::new(field.name(), index));
+        projection_exprs.push((column_expr, field.name().clone()));
+    }
+
+    let partition_expr = Arc::new(PartitionExpr::new(calculator));
+    projection_exprs.push((partition_expr, 
PARTITION_VALUES_COLUMN.to_string()));
+
+    let projection = ProjectionExec::try_new(projection_exprs, input)?;
+    Ok(Arc::new(projection))
+}
+
+/// PhysicalExpr implementation for partition value calculation
+#[derive(Debug, Clone)]
+struct PartitionExpr {
+    calculator: Arc<Mutex<PartitionValueCalculator>>,
+}
+
+impl PartitionExpr {
+    fn new(calculator: PartitionValueCalculator) -> Self {
+        Self {
+            calculator: Arc::new(Mutex::new(calculator)),
+        }
+    }
+}
+
+// Manual PartialEq/Eq implementations for pointer-based equality
+// (two PartitionExpr are equal if they share the same calculator instance)
+impl PartialEq for PartitionExpr {
+    fn eq(&self, other: &Self) -> bool {
+        Arc::ptr_eq(&self.calculator, &other.calculator)
+    }
+}
+
+impl Eq for PartitionExpr {}
+
+impl PhysicalExpr for PartitionExpr {
+    fn as_any(&self) -> &dyn std::any::Any {
+        self
+    }
+
+    fn data_type(&self, _input_schema: &ArrowSchema) -> DFResult<DataType> {
+        let calculator = self
+            .calculator
+            .lock()
+            .map_err(|e| DataFusionError::Internal(format!("Failed to lock 
calculator: {}", e)))?;
+        Ok(calculator.partition_type.clone())
+    }
+
+    fn nullable(&self, _input_schema: &ArrowSchema) -> DFResult<bool> {
+        Ok(false)
+    }
+
+    fn evaluate(&self, batch: &RecordBatch) -> DFResult<ColumnarValue> {
+        let mut calculator = self
+            .calculator
+            .lock()
+            .map_err(|e| DataFusionError::Internal(format!("Failed to lock 
calculator: {}", e)))?;
+        let array = calculator.calculate(batch)?;
+        Ok(ColumnarValue::Array(array))
+    }
+
+    fn children(&self) -> Vec<&Arc<dyn PhysicalExpr>> {
+        vec![]
+    }
+
+    fn with_new_children(
+        self: Arc<Self>,
+        _children: Vec<Arc<dyn PhysicalExpr>>,
+    ) -> DFResult<Arc<dyn PhysicalExpr>> {
+        Ok(self)
+    }
+
+    fn fmt_sql(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        if let Ok(calculator) = self.calculator.lock() {
+            let field_names: Vec<String> = calculator
+                .partition_spec
+                .fields()
+                .iter()
+                .map(|pf| format!("{}({})", pf.transform, pf.name))
+                .collect();
+            write!(f, "iceberg_partition_values[{}]", field_names.join(", "))
+        } else {
+            write!(f, "iceberg_partition_values")
+        }
+    }
+}
+
+impl std::fmt::Display for PartitionExpr {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        if let Ok(calculator) = self.calculator.lock() {
+            let field_names: Vec<&str> = calculator
+                .partition_spec
+                .fields()
+                .iter()
+                .map(|pf| pf.name.as_str())
+                .collect();
+            write!(f, "iceberg_partition_values({})", field_names.join(", "))
+        } else {
+            write!(f, "iceberg_partition_values")
+        }
+    }
+}
+
+impl std::hash::Hash for PartitionExpr {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        std::any::TypeId::of::<Self>().hash(state);
+    }
+}
+
+/// Calculator for partition values in Iceberg tables
+#[derive(Debug, Clone)]
+struct PartitionValueCalculator {
+    partition_spec: PartitionSpec,
+    table_schema: Schema,
+    partition_type: DataType,
+    projector: Option<RecordBatchProjector>,
+}
+
+impl PartitionValueCalculator {
+    fn new(
+        partition_spec: PartitionSpec,
+        table_schema: Schema,
+        partition_type: DataType,
+    ) -> DFResult<Self> {
+        if partition_spec.is_unpartitioned() {
+            return Err(DataFusionError::Internal(
+                "Cannot create partition calculator for unpartitioned 
table".to_string(),
+            ));
+        }
+
+        Ok(Self {
+            partition_spec,
+            table_schema,
+            partition_type,
+            projector: None,
+        })
+    }
+
+    fn calculate(&mut self, batch: &RecordBatch) -> DFResult<ArrayRef> {
+        if self.projector.is_none() {
+            let source_field_ids: Vec<i32> = self
+                .partition_spec
+                .fields()
+                .iter()
+                .map(|pf| pf.source_id)
+                .collect();
+
+            let projector = RecordBatchProjector::from_iceberg_schema_mapping(

Review Comment:
   We don't need first batch to get input's schema, see: 
https://github.com/apache/datafusion/blob/921f4a028409f71b68bed7d05a348255bb6f0fba/datafusion/physical-plan/src/execution_plan.rs#L106



##########
crates/iceberg/src/arrow/record_batch_projector.rs:
##########
@@ -77,6 +79,80 @@ impl RecordBatchProjector {
         })
     }
 
+    /// Create RecordBatchProjector using Iceberg schema for field mapping.
+    ///
+    /// This constructor is more flexible and works with any Arrow schema by 
using
+    /// the Iceberg schema to map field names to field IDs.
+    ///
+    /// # Arguments
+    /// * `original_schema` - The original Arrow schema (doesn't need field ID 
metadata)
+    /// * `iceberg_schema` - The Iceberg schema for field ID mapping
+    /// * `target_field_ids` - The field IDs to project
+    pub fn from_iceberg_schema_mapping(
+        original_schema: SchemaRef,
+        iceberg_schema: Arc<IcebergSchema>,
+        target_field_ids: &[i32],
+    ) -> Result<Self> {
+        let field_id_fetch_func = |field: &Field| -> Result<Option<i64>> {
+            // First try to get field ID from metadata (Parquet case)
+            if let Some(value) = 
field.metadata().get(PARQUET_FIELD_ID_META_KEY) {
+                let field_id = value.parse::<i32>().map_err(|e| {
+                    Error::new(
+                        ErrorKind::DataInvalid,
+                        "Failed to parse field id".to_string(),
+                    )
+                    .with_context("value", value)
+                    .with_source(e)
+                })?;
+                return Ok(Some(field_id as i64));
+            }
+
+            // Fallback: use Iceberg schema's built-in field lookup
+            if let Some(iceberg_field) = 
iceberg_schema.field_by_name(field.name()) {

Review Comment:
   This is incorrect. Iceberg schema's `field_by_name` uses full path(including 
parent name), while this is not name.



##########
crates/integrations/datafusion/src/physical_plan/project.rs:
##########
@@ -15,125 +15,203 @@
 // specific language governing permissions and limitations
 // under the License.
 
-//! Utilities for calculating partition values for Iceberg tables.
-//!
-//! This module provides functions to calculate partition values from record 
batches
-//! based on Iceberg partition specifications. These utilities are used when 
writing
-//! data to partitioned Iceberg tables.
+//! Partition value projection for Iceberg tables.
 
 use std::sync::Arc;
 
 use datafusion::arrow::array::{ArrayRef, RecordBatch, StructArray};
-use datafusion::arrow::datatypes::{
-    DataType, Field, Schema as ArrowSchema, SchemaRef as ArrowSchemaRef,
-};
+use datafusion::arrow::datatypes::{DataType, Schema as ArrowSchema};
 use datafusion::common::Result as DFResult;
 use datafusion::error::DataFusionError;
+use datafusion::physical_expr::PhysicalExpr;
+use datafusion::physical_expr::expressions::Column;
+use datafusion::physical_plan::projection::ProjectionExec;
+use datafusion::physical_plan::{ColumnarValue, ExecutionPlan};
 use iceberg::spec::{PartitionSpec, Schema};
+use iceberg::table::Table;
 
 use crate::to_datafusion_error;
 
 /// Column name for the combined partition values struct
-#[allow(dead_code)]
-pub(crate) const PARTITION_VALUES_COLUMN: &str = "_iceberg_partition_values";
+const PARTITION_VALUES_COLUMN: &str = "_partition";
 
-/// Create an output schema by adding a single partition values struct column 
to the input schema.
-/// Returns the original schema unchanged if the table is unpartitioned.
+/// Extends an ExecutionPlan with partition value calculations for Iceberg 
tables.
+///
+/// This function takes an input ExecutionPlan and extends it with an 
additional column
+/// containing calculated partition values based on the table's partition 
specification.
+/// For unpartitioned tables, returns the original plan unchanged.
+///
+/// # Arguments
+/// * `input` - The input ExecutionPlan to extend
+/// * `table` - The Iceberg table with partition specification
+///
+/// # Returns
+/// * `Ok(Arc<dyn ExecutionPlan>)` - Extended plan with partition values column
+/// * `Err` - If partition spec is not found or transformation fails
 #[allow(dead_code)]
-pub(crate) fn create_schema_with_partition_columns(
-    input_schema: &ArrowSchema,
-    partition_spec: &PartitionSpec,
-    table_schema: &Schema,
-) -> DFResult<ArrowSchemaRef> {
+pub fn project_with_partition(
+    input: Arc<dyn ExecutionPlan>,
+    table: &Table,
+) -> DFResult<Arc<dyn ExecutionPlan>> {
+    let metadata = table.metadata();
+    let partition_spec = metadata
+        .partition_spec_by_id(metadata.default_partition_spec_id())
+        .ok_or_else(|| DataFusionError::Internal("Default partition spec not 
found".to_string()))?;
+    let table_schema = metadata.current_schema();
+
     if partition_spec.is_unpartitioned() {
-        return Ok(Arc::new(input_schema.clone()));
+        return Ok(input);
     }
 
-    let mut fields: Vec<Arc<Field>> = input_schema.fields().to_vec();
+    let input_schema = input.schema();
+    let partition_type = build_partition_type(partition_spec, 
table_schema.as_ref())?;
+    let calculator = PartitionValueCalculator::new(
+        partition_spec.as_ref().clone(),
+        table_schema.as_ref().clone(),
+        partition_type,
+    );
 
-    let partition_struct_type = partition_spec
-        .partition_type(table_schema)
-        .map_err(to_datafusion_error)?;
+    let mut projection_exprs: Vec<(Arc<dyn PhysicalExpr>, String)> = 
Vec::new();
 
-    let arrow_struct_type =
-        
iceberg::arrow::type_to_arrow_type(&iceberg::spec::Type::Struct(partition_struct_type))
-            .map_err(to_datafusion_error)?;
+    for (index, field) in input_schema.fields().iter().enumerate() {
+        let column_expr = Arc::new(Column::new(field.name(), index));
+        projection_exprs.push((column_expr, field.name().clone()));
+    }
 
-    fields.push(Arc::new(Field::new(
-        PARTITION_VALUES_COLUMN,
-        arrow_struct_type,
-        false, // Partition values are generally not null
-    )));
+    let partition_expr = Arc::new(PartitionExpr::new(calculator));
+    projection_exprs.push((partition_expr, 
PARTITION_VALUES_COLUMN.to_string()));
 
-    Ok(Arc::new(ArrowSchema::new(fields)))
+    let projection = ProjectionExec::try_new(projection_exprs, input)?;
+    Ok(Arc::new(projection))
 }
 
-/// Calculate partition values for a record batch and return as a single 
struct array.
-/// Returns None if the table is unpartitioned.
-///
-/// # Arguments
-/// * `batch` - The record batch to calculate partition values for
-/// * `partition_spec` - The partition specification defining the partition 
fields
-/// * `table_schema` - The Iceberg table schema
-/// * `expected_partition_type` - The expected Arrow struct type for the 
partition values
-#[allow(dead_code)]
-pub(crate) fn calculate_partition_values(
-    batch: &RecordBatch,
-    partition_spec: &PartitionSpec,
-    table_schema: &Schema,
-    expected_partition_type: &DataType,
-) -> DFResult<Option<ArrayRef>> {
-    if partition_spec.is_unpartitioned() {
-        return Ok(None);
+/// PhysicalExpr implementation for partition value calculation
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct PartitionExpr {
+    calculator: PartitionValueCalculator,
+}
+
+impl PartitionExpr {
+    fn new(calculator: PartitionValueCalculator) -> Self {
+        Self { calculator }
+    }
+}
+
+impl PhysicalExpr for PartitionExpr {
+    fn as_any(&self) -> &dyn std::any::Any {
+        self
+    }
+
+    fn data_type(&self, _input_schema: &ArrowSchema) -> DFResult<DataType> {
+        Ok(self.calculator.partition_type.clone())
+    }
+
+    fn nullable(&self, _input_schema: &ArrowSchema) -> DFResult<bool> {
+        Ok(false)
+    }
+
+    fn evaluate(&self, batch: &RecordBatch) -> DFResult<ColumnarValue> {
+        let array = self.calculator.calculate(batch)?;
+        Ok(ColumnarValue::Array(array))
+    }
+
+    fn children(&self) -> Vec<&Arc<dyn PhysicalExpr>> {
+        vec![]
     }
 
-    let batch_schema = batch.schema();
-    let mut partition_values = 
Vec::with_capacity(partition_spec.fields().len());
+    fn with_new_children(
+        self: Arc<Self>,
+        _children: Vec<Arc<dyn PhysicalExpr>>,
+    ) -> DFResult<Arc<dyn PhysicalExpr>> {
+        Ok(self)
+    }
+
+    fn fmt_sql(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "partition_values")
+    }
+}
+
+impl std::fmt::Display for PartitionExpr {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "partition_values")
+    }
+}
+
+impl std::hash::Hash for PartitionExpr {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        std::any::TypeId::of::<Self>().hash(state);
+    }
+}
+
+/// Calculator for partition values in Iceberg tables
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct PartitionValueCalculator {
+    partition_spec: PartitionSpec,
+    table_schema: Schema,
+    partition_type: DataType,
+}
 
-    let expected_struct_fields = match expected_partition_type {
-        DataType::Struct(fields) => fields.clone(),
-        _ => {
+impl PartitionValueCalculator {
+    fn new(partition_spec: PartitionSpec, table_schema: Schema, 
partition_type: DataType) -> Self {
+        Self {
+            partition_spec,
+            table_schema,
+            partition_type,
+        }
+    }
+
+    fn calculate(&self, batch: &RecordBatch) -> DFResult<ArrayRef> {
+        if self.partition_spec.is_unpartitioned() {
             return Err(DataFusionError::Internal(
-                "Expected partition type must be a struct".to_string(),
+                "Cannot calculate partition values for unpartitioned 
table".to_string(),
             ));
         }
-    };
 
-    for pf in partition_spec.fields() {
-        let source_field = 
table_schema.field_by_id(pf.source_id).ok_or_else(|| {
-            DataFusionError::Internal(format!(
-                "Source field not found with id {} when calculating partition 
values",
-                pf.source_id
-            ))
-        })?;
+        let batch_schema = batch.schema();
+        let mut partition_values = 
Vec::with_capacity(self.partition_spec.fields().len());
+
+        let expected_struct_fields = match &self.partition_type {
+            DataType::Struct(fields) => fields.clone(),
+            _ => {
+                return Err(DataFusionError::Internal(
+                    "Expected partition type must be a struct".to_string(),
+                ));
+            }
+        };
+
+        for pf in self.partition_spec.fields() {
+            let source_field = 
self.table_schema.field_by_id(pf.source_id).ok_or_else(|| {
+                DataFusionError::Internal(format!(
+                    "Source field not found with id {} when calculating 
partition values",
+                    pf.source_id
+                ))
+            })?;
 
-        let field_path = find_field_path(table_schema, source_field.id)?;
-        let index_path = resolve_arrow_index_path(batch_schema.as_ref(), 
&field_path)?;
+            let field_path = find_field_path(&self.table_schema, 
source_field.id)?;
+            let index_path = resolve_arrow_index_path(batch_schema.as_ref(), 
&field_path)?;
 
-        let source_column = extract_column_by_index_path(batch, &index_path)?;
+            let source_column = extract_column_by_index_path(batch, 
&index_path)?;
 
-        let transform_fn = 
iceberg::transform::create_transform_function(&pf.transform)
-            .map_err(to_datafusion_error)?;
-        let partition_value = transform_fn
-            .transform(source_column)
-            .map_err(to_datafusion_error)?;
+            let transform_fn = 
iceberg::transform::create_transform_function(&pf.transform)

Review Comment:
   This is not resolved, we could create trnasform functions in constructor.



##########
crates/iceberg/src/arrow/record_batch_projector.rs:
##########
@@ -77,6 +79,80 @@ impl RecordBatchProjector {
         })
     }
 
+    /// Create RecordBatchProjector using Iceberg schema for field mapping.
+    ///
+    /// This constructor is more flexible and works with any Arrow schema by 
using
+    /// the Iceberg schema to map field names to field IDs.
+    ///
+    /// # Arguments
+    /// * `original_schema` - The original Arrow schema (doesn't need field ID 
metadata)
+    /// * `iceberg_schema` - The Iceberg schema for field ID mapping
+    /// * `target_field_ids` - The field IDs to project
+    pub fn from_iceberg_schema_mapping(
+        original_schema: SchemaRef,
+        iceberg_schema: Arc<IcebergSchema>,
+        target_field_ids: &[i32],
+    ) -> Result<Self> {
+        let field_id_fetch_func = |field: &Field| -> Result<Option<i64>> {

Review Comment:
   This method is unnecessarily to be too complicated, following approach could 
simplify this:
   1. Create an arrow schema using iceberg schema.
   2. Prune arrow schema created in step 1 by matching top level field name.
   
   Then we can pass pruned arrow schema to original constructor, and search 
field by `PARQUET_FIELD_ID_META_KEY`



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