[bugfix](iceberg)fix read NULL with date partition

fe/fe-core/src/main/java/org/apache/doris/planner/external/iceberg/IcebergScanNode.java

@@ -69,6 +69,9 @@
 import org.apache.iceberg.expressions.Expression;
 import org.apache.iceberg.io.CloseableIterable;
 import org.apache.iceberg.types.Conversions;
+import org.apache.iceberg.types.Type;
+import org.apache.iceberg.types.Types;
+import org.apache.iceberg.util.DateTimeUtil;
 import org.apache.iceberg.util.TableScanUtil;
 
 import java.io.IOException;
@@ -218,11 +221,23 @@ private List<Split> doGetSplits() throws UserException {
                 List<String> partitionValues = new ArrayList<>();
                 if (isPartitionedTable) {
                     StructLike structLike = splitTask.file().partition();
+                    List<PartitionField> fields = splitTask.spec().fields();
+                    Types.StructType structType = icebergTable.schema().asStruct();
 
                     // set partitionValue for this IcebergSplit
                     for (int i = 0; i < structLike.size(); i++) {
-                        String partition = String.valueOf(structLike.get(i, Object.class));
-                        partitionValues.add(partition);
+                        Object obj = structLike.get(i, Object.class);
+                        String value = String.valueOf(obj);
+                        PartitionField partitionField = fields.get(i);
+                        if (partitionField.transform().isIdentity()) {
+                            Type type = structType.fieldType(partitionField.name());
+                            if (type != null && type.typeId().equals(Type.TypeID.DATE)) {
+                                // iceberg use integer to store date,
+                                // we need transform it to string
+                                value = DateTimeUtil.daysToIsoDate((Integer) obj);
+                            }
+                        }
+                        partitionValues.add(value);
                     }
 
                     // Counts the number of partitions read

regression-test/data/external_table_p2/iceberg/test_external_catalog_iceberg_partition.out

@@ -71,3 +71,36 @@
 -- !q09 --
 100	0.3	test3	2023-01-03T00:00
 
+-- !q01 --
+1	true	2020-01-02	2020-01-02T01:02:03.123456
+
+-- !q02 --
+1	true	2020-01-02	2020-01-02T01:02:03.123456
+
+-- !q03 --
+1	true	2020-01-02	2020-01-02T01:02:03.123456
+
+-- !q04 --
+1	true	2020-01-02	2020-01-02T01:02:03.123456
+
+-- !q05 --
+1	true	2020-01-02	2020-01-02T01:02:03.123456
+
+-- !q06 --
+1	2020-01-02
+
+-- !q07 --
+1	2020-01-02
+
+-- !q08 --
+1	2020-01-02
+
+-- !q09 --
+1	2020-01-02
+
+-- !q10 --
+1	2020-01-02
+
+-- !q11 --
+1	2020-01-02
+

regression-test/suites/external_table_p2/iceberg/test_external_catalog_iceberg_partition.groovy

@@ -55,9 +55,30 @@ suite("test_external_catalog_iceberg_partition", "p2") {
             qt_q08 """ select * from iceberg_catalog.orc_partitioned_truncate_and_fields where t_int is null order by t_float """
             qt_q09 """ select * from iceberg_catalog.orc_partitioned_truncate_and_fields where t_int is not null order by t_float """
         }
+
+        // test date for partition and predict
+        def q01_date = {
+
+            qt_q01 """ select * from user_case_date_without_partition where d = '2020-01-02' """
+            qt_q02 """ select * from user_case_date_without_partition where d > '2020-01-01' """
+            qt_q03 """ select * from user_case_date_without_partition where d < '2020-01-03' """
+            qt_q04 """ select * from user_case_date_without_partition where ts < '2020-01-03' """
+            qt_q05 """ select * from user_case_date_without_partition where ts > '2020-01-01' """
+
+            qt_q06 """ select * from user_case_date_with_date_partition where d = '2020-01-02' """
+            qt_q07 """ select * from user_case_date_with_date_partition where d < '2020-01-03' """
+            qt_q08 """ select * from user_case_date_with_date_partition where d > '2020-01-01' """
+
+            qt_q09 """ select * from user_case_date_with_days_date_partition where d = '2020-01-02' """
+            qt_q10 """ select * from user_case_date_with_days_date_partition where d < '2020-01-03' """
+            qt_q11 """ select * from user_case_date_with_days_date_partition where d > '2020-01-01' """
+
+        }
+
         sql """ use `iceberg_catalog`; """
         q01_parquet()
         q01_orc()
+        q01_date()
     }
 }