Add Projections

api/src/main/java/org/apache/iceberg/transforms/Bucket.java

@@ -113,6 +113,7 @@ public UnboundPredicate<Integer> project(String name, BoundPredicate<T> predicat
             predicate.op(), name, apply(predicate.literal().value()));
 //      case IN:
 //        return Expressions.predicate();
+      case STARTS_WITH:
       default:
         // comparison predicates can't be projected, notEq can't be projected
         // TODO: small ranges can be projected.

api/src/main/java/org/apache/iceberg/transforms/ProjectionUtil.java

@@ -197,6 +197,8 @@ static <S, T> UnboundPredicate<T> truncateArray(
         return predicate(Expression.Operation.GT_EQ, name, transform.apply(boundary));
       case EQ:
         return predicate(Expression.Operation.EQ, name, transform.apply(boundary));
+      case STARTS_WITH:
+        return predicate(Expression.Operation.STARTS_WITH, name, transform.apply(boundary));
 //        case IN: // TODO
 //          return Expressions.predicate(Operation.IN, name, transform.apply(boundary));
       default:

api/src/main/java/org/apache/iceberg/transforms/Truncate.java

@@ -243,17 +243,35 @@ public boolean canTransform(Type type) {
 
     @Override
     public UnboundPredicate<CharSequence> project(String name,
-                                                  BoundPredicate<CharSequence> pred) {
-      if (pred.op() == NOT_NULL || pred.op() == IS_NULL) {
-        return Expressions.predicate(pred.op(), name);
+                                                  BoundPredicate<CharSequence> predicate) {
+      switch (predicate.op()) {
+        case NOT_NULL:
+        case IS_NULL:
+          return Expressions.predicate(predicate.op(), name);
+        case STARTS_WITH:
+          if (predicate.literal().value().length() <= width()) {
+            return Expressions.predicate(predicate.op(), name, predicate.literal().value());
+          } else {
+            return ProjectionUtil.truncateArray(name, predicate, this);
+          }
+        default:
+          return ProjectionUtil.truncateArray(name, predicate, this);
       }
-      return ProjectionUtil.truncateArray(name, pred, this);
     }
 
     @Override
     public UnboundPredicate<CharSequence> projectStrict(String name,
                                                         BoundPredicate<CharSequence> predicate) {
-      return null;
+      switch (predicate.op()) {
+        case STARTS_WITH:
+          if (predicate.literal().value().length() <= width()) {
+            return Expressions.predicate(predicate.op(), name, predicate.literal().value());
+          } else {
+            return null;
+          }
+        default:
+          return null;
+      }
     }
 
     @Override

api/src/test/java/org/apache/iceberg/transforms/TestStartsWith.java

@@ -0,0 +1,93 @@
+/*
+ * 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.iceberg.transforms;
+
+import org.apache.iceberg.PartitionSpec;
+import org.apache.iceberg.Schema;
+import org.apache.iceberg.TestHelpers;
+import org.apache.iceberg.expressions.Binder;
+import org.apache.iceberg.expressions.BoundPredicate;
+import org.apache.iceberg.expressions.Evaluator;
+import org.apache.iceberg.expressions.Expression;
+import org.apache.iceberg.expressions.Literal;
+import org.apache.iceberg.expressions.Projections;
+import org.apache.iceberg.expressions.UnboundPredicate;
+import org.apache.iceberg.types.Types;
+import org.junit.Assert;
+import org.junit.Test;
+
+import static org.apache.iceberg.TestHelpers.assertAndUnwrapUnbound;
+import static org.apache.iceberg.expressions.Expressions.startsWith;
+import static org.apache.iceberg.types.Types.NestedField.optional;
+import static org.apache.iceberg.types.Types.NestedField.required;
+
+public class TestStartsWith {
+
+  private static final Schema SCHEMA = new Schema(optional(1, "someStringCol", Types.StringType.get()));
+
+  @Test
+  public void assertTruncateProjections() {
+    PartitionSpec spec = PartitionSpec.builderFor(SCHEMA).truncate("someStringCol", 4).build();
+
+    assertProjectionInclusive(spec, startsWith("someStringCol", "ab"), "ab");
+    assertProjectionInclusive(spec, startsWith("someStringCol", "abab"), "abab");
+    assertProjectionInclusive(spec, startsWith("someStringCol", "ababab"), "abab");
+
+    assertProjectionStrict(spec, startsWith("someStringCol", "ab"), "ab");
+    assertProjectionStrict(spec, startsWith("someStringCol", "abab"), "abab");
+  }
+
+  @Test
+  public void assertTruncateString() {
+    Types.StructType struct = Types.StructType.of(required(0, "s", Types.StringType.get()));
+    Truncate<String> trunc = Truncate.get(Types.StringType.get(), 2);
+    Expression expr = startsWith("s", "abcde");
+    BoundPredicate<String> boundExpr = (BoundPredicate<String>) Binder.bind(struct,  expr, false);
+
+    UnboundPredicate<String> projected = trunc.project("s", boundExpr);
+    Evaluator evaluator = new Evaluator(struct, projected);
+
+    Assert.assertTrue("startsWith(abcde, truncate(abcde,2))  => true",
+        evaluator.eval(TestHelpers.Row.of("abcde")));
+  }
+
+  private void assertProjectionInclusive(PartitionSpec spec, UnboundPredicate<?> filter,
+                                         String expectedLiteral) {
+    Expression projection = Projections.inclusive(spec).project(filter);
+    assertProjection(spec, expectedLiteral, projection);
+  }
+
+  private void assertProjectionStrict(PartitionSpec spec, UnboundPredicate<?> filter,
+                                         String expectedLiteral) {
+    Expression projection = Projections.strict(spec).project(filter);
+    assertProjection(spec, expectedLiteral, projection);
+  }
+
+  private void assertProjection(PartitionSpec spec, String expectedLiteral, Expression projection) {
+    UnboundPredicate<?> predicate = assertAndUnwrapUnbound(projection);
+
+    Assert.assertEquals(predicate.op(), Expression.Operation.STARTS_WITH);
+
+    Literal literal = predicate.literal();
+    Truncate<CharSequence> transform = (Truncate<CharSequence>) spec.getFieldsBySourceId(1).get(0).transform();
+    String output = transform.toHumanString((String) literal.value());
+    Assert.assertEquals(expectedLiteral, output);
+  }
+}

api/src/test/java/org/apache/iceberg/transforms/TestTruncate.java

@@ -21,14 +21,10 @@
 
 import java.math.BigDecimal;
 import java.nio.ByteBuffer;
-import org.apache.iceberg.TestHelpers;
-import org.apache.iceberg.expressions.*;
 import org.apache.iceberg.types.Types;
 import org.junit.Assert;
 import org.junit.Test;
 
-import static org.apache.iceberg.expressions.Expressions.startsWith;
-import static org.apache.iceberg.types.Types.NestedField.required;
 public class TestTruncate {
   @Test
   public void testTruncateInteger() {
@@ -80,20 +76,6 @@ public void testTruncateString() {
         "abc", trunc.apply("abc"));
   }
 
-  @Test
-  public void testTruncateStringStartsWith() {
-    Types.StructType struct = Types.StructType.of(required(0, "s", Types.StringType.get()));
-    Truncate<String> trunc = Truncate.get(Types.StringType.get(), 2);
-    Expression expr = startsWith("s", "abcde");
-    BoundPredicate<String> boundExpr = (BoundPredicate<String>) Binder.bind(struct,  expr, false);
-
-    UnboundPredicate<String> projected = trunc.project("s", boundExpr);
-    Evaluator evaluator = new Evaluator(struct, projected);
-
-    Assert.assertTrue("startsWith(abcde, truncate(abcde,2))  => true",
-            evaluator.eval(TestHelpers.Row.of(("abcde"))));
-  }
-
   @Test
   public void testTruncateByteBuffer() throws Exception {
     Truncate<ByteBuffer> trunc = Truncate.get(Types.BinaryType.get(), 4);