[core][spark] Introduce upper transform

paimon-common/src/main/java/org/apache/paimon/predicate/UpperTransform.java

@@ -0,0 +1,50 @@
+/*
+ * 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.
+ */
+
+package org.apache.paimon.predicate;
+
+import org.apache.paimon.data.BinaryString;
+
+import java.util.List;
+
+import static org.apache.paimon.utils.Preconditions.checkArgument;
+
+/** Upper {@link Transform}. */
+public class UpperTransform extends StringTransform {
+
+    private static final long serialVersionUID = 1L;
+
+    public UpperTransform(List<Object> inputs) {
+        super(inputs);
+        checkArgument(inputs.size() == 1);
+    }
+
+    @Override
+    public BinaryString transform(List<BinaryString> inputs) {
+        BinaryString string = inputs.get(0);
+        if (string == null) {
+            return null;
+        }
+        return string.toUpperCase();
+    }
+
+    @Override
+    public Transform copyWithNewInputs(List<Object> inputs) {
+        return new UpperTransform(inputs);
+    }
+}

paimon-common/src/test/java/org/apache/paimon/predicate/UpperTransformTest.java

@@ -0,0 +1,60 @@
+/*
+ * 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.
+ */
+
+package org.apache.paimon.predicate;
+
+import org.apache.paimon.data.BinaryString;
+import org.apache.paimon.data.GenericRow;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+class UpperTransformTest {
+
+    @Test
+    public void testNullInputs() {
+        List<Object> inputs = new ArrayList<>();
+        inputs.add(null);
+        UpperTransform transform = new UpperTransform(inputs);
+        Object result = transform.transform(GenericRow.of());
+        assertThat(result).isNull();
+    }
+
+    @Test
+    public void testNormalInputs() {
+        List<Object> inputs = new ArrayList<>();
+        inputs.add(BinaryString.fromString("hello"));
+        UpperTransform transform = new UpperTransform(inputs);
+        Object result = transform.transform(GenericRow.of());
+        assertThat(result).isEqualTo(BinaryString.fromString("HELLO"));
+    }
+
+    @Test
+    public void testIllegalInputs() {
+        List<Object> inputs = new ArrayList<>();
+        inputs.add(BinaryString.fromString("hello"));
+        inputs.add(BinaryString.fromString("hi"));
+        assertThatThrownBy(() -> new UpperTransform(inputs))
+                .isInstanceOf(IllegalArgumentException.class);
+    }
+}

paimon-spark/paimon-spark-common/src/main/scala/org/apache/paimon/spark/util/SparkExpressionConverter.scala

@@ -19,7 +19,7 @@
 package org.apache.paimon.spark.util
 
 import org.apache.paimon.data.{BinaryString, Decimal, Timestamp}
-import org.apache.paimon.predicate.{ConcatTransform, FieldRef, FieldTransform, Transform}
+import org.apache.paimon.predicate.{ConcatTransform, FieldRef, FieldTransform, Transform, UpperTransform}
 import org.apache.paimon.spark.SparkTypeUtils
 import org.apache.paimon.spark.util.shim.TypeUtils.treatPaimonTimestampTypeAsSparkTimestampType
 import org.apache.paimon.types.{DecimalType, RowType}
@@ -34,6 +34,7 @@ object SparkExpressionConverter {
 
   // Supported transform names
   private val CONCAT = "CONCAT"
+  private val UPPER = "UPPER"
 
   /** Convert Spark [[Expression]] to Paimon [[Transform]], return None if not supported. */
   def toPaimonTransform(exp: Expression, rowType: RowType): Option[Transform] = {
@@ -48,6 +49,13 @@ object SparkExpressionConverter {
               case _ => return None
             }
             Some(new ConcatTransform(inputs.toList.asJava))
+          case UPPER =>
+            val inputs = exp.children().map {
+              case n: NamedReference => toPaimonFieldRef(n, rowType)
+              case l: Literal[_] => toPaimonLiteral(l)
+              case _ => return None
+            }
+            Some(new UpperTransform(inputs.toList.asJava))
           case _ => None
         }
       case _ => None

paimon-spark/paimon-spark-ut/src/test/scala/org/apache/paimon/spark/sql/PaimonPushDownTestBase.scala

@@ -129,6 +129,36 @@ abstract class PaimonPushDownTestBase extends PaimonSparkTestBase {
     }
   }
 
+  test(s"Paimon push down: apply UPPER") {
+    // Spark support push down UPPER since Spark 3.4.
+    if (gteqSpark3_4) {
+      withTable("t") {
+        sql("""
+              |CREATE TABLE t (id int, value int, dt STRING)
+              |using paimon
+              |PARTITIONED BY (dt)
+              |""".stripMargin)
+
+        sql("""
+              |INSERT INTO t values
+              |(1, 100, 'hello')
+              |""".stripMargin)
+
+        val q =
+          """
+            |SELECT * FROM t
+            |WHERE UPPER(dt) = 'HELLO'
+            |""".stripMargin
+        assert(!checkFilterExists(q))
+
+        checkAnswer(
+          spark.sql(q),
+          Seq(Row(1, 100, "hello"))
+        )
+      }
+    }
+  }
+
   test("Paimon pushDown: limit for append-only tables with deletion vector") {
     withTable("dv_test") {
       spark.sql(