update

kernel/kernel-api/src/main/java/io/delta/kernel/expressions/Column.java

@@ -19,7 +19,6 @@
 import java.util.Collections;
 import java.util.List;
 
-import io.delta.kernel.types.DataType;
 import io.delta.kernel.types.StructType;
 
 /**
@@ -36,24 +35,24 @@
 public final class Column implements Expression {
     private final int ordinal;
     private final String name;
-    private final DataType dataType;
 
-    public Column(int ordinal, String name, DataType dataType) {
+    public Column(int ordinal, String name) {
         this.ordinal = ordinal;
         this.name = name;
-        this.dataType = dataType;
-    }
-
-    public String getName() {
-        return name;
     }
 
+    /**
+     * @return the ordinal of the column in the input columnar batch.
+     */
     public int getOrdinal() {
         return ordinal;
     }
 
-    public DataType getDataType() {
-        return dataType;
+    /**
+     * @return the column name.
+     */
+    public String getName() {
+        return name;
     }
 
     @Override

kernel/kernel-api/src/main/java/io/delta/kernel/expressions/Expression.java

@@ -18,14 +18,9 @@
 import java.util.List;
 
 /**
- * Base interface for all Kernel expression
+ * Base interface for all Kernel expressions.
  */
 public interface Expression {
-    /**
-     * @return the String representation of this expression.
-     */
-    String toString();
-
     /**
      * @return a {@link List} of the immediate children of this node
      */

kernel/kernel-api/src/main/java/io/delta/kernel/expressions/predicate/AlwaysFalse.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (2023) The Delta Lake Project Authors.
+ *
+ * Licensed 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 io.delta.kernel.expressions.predicate;
+
+import java.util.Collections;
+
+/**
+ * Predicate which always evaluates to {@code false}.
+ */
+public final class AlwaysFalse extends Predicate {
+    public AlwaysFalse() {
+        super("ALWAYS_FALSE", Collections.emptyList());
+    }
+
+    @Override
+    public String toString() {
+        return "false";
+    }
+}

kernel/kernel-api/src/main/java/io/delta/kernel/expressions/predicate/AlwaysTrue.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright (2023) The Delta Lake Project Authors.
+ *
+ * Licensed 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 io.delta.kernel.expressions.predicate;
+
+import java.util.Collections;
+
+/**
+ * Predicate which always evaluates to {@code true}.
+ */
+public final class AlwaysTrue extends Predicate {
+    public AlwaysTrue() {
+        super("ALWAYS_TRUE", Collections.emptyList());
+    }
+
+    @Override
+    public String toString() {
+        return "true";
+    }
+}

kernel/kernel-api/src/main/java/io/delta/kernel/expressions/And.java → kernel/kernel-api/src/main/java/io/delta/kernel/expressions/predicate/And.java

@@ -13,23 +13,24 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package io.delta.kernel.expressions;
+package io.delta.kernel.expressions.predicate;
 
 import java.util.Arrays;
 
 /**
  * {@code AND} expression
  * <p>
  * Definition:
- * <p><ul>
- * <li>Logical {@code expr1} AND {@code expr2} on two inputs.</li>
- * <li>Requires both left and right input expressions evaluate to be {@link Predicate}.</li>
- * <li>Result is null if one or both of the inputs are null.</li>
+ * <p>
+ * <ul>
+ *     <li>Logical {@code expr1} AND {@code expr2} on two inputs.</li>
+ *     <li>Requires both left and right input expressions evaluate to be {@link Predicate}.</li>
+ *     <li>Result is null if one or both of the inputs are null.</li>
  * </ul>
  */
 public final class And extends Predicate {
     public And(Predicate left, Predicate right) {
-        super(Arrays.asList(left, right));
+        super("AND", Arrays.asList(left, right));
     }
 
     /**

kernel/kernel-api/src/main/java/io/delta/kernel/expressions/Or.java → kernel/kernel-api/src/main/java/io/delta/kernel/expressions/predicate/Or.java

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-package io.delta.kernel.expressions;
+package io.delta.kernel.expressions.predicate;
 
 import java.util.Arrays;
 
@@ -29,7 +29,7 @@
  */
 public final class Or extends Predicate {
     public Or(Predicate left, Predicate right) {
-        super(Arrays.asList(left, right));
+        super("OR", Arrays.asList(left, right));
     }
 
     /**