[FLINK-12253][table-common] Add a VARCHAR type

flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/logical/LogicalTypeVisitor.java

@@ -31,5 +31,7 @@ public interface LogicalTypeVisitor<R> {
 
 	R visit(CharType charType);
 
+	R visit(VarCharType varCharType);
+
 	R visit(LogicalType other);
 }

flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/logical/VarCharType.java

@@ -0,0 +1,134 @@
+/*
+ * 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.flink.table.types.logical;
+
+import org.apache.flink.annotation.PublicEvolving;
+import org.apache.flink.table.api.ValidationException;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+
+/**
+ * Logical type of a variable-length character string.
+ *
+ * <p>The serialized string representation is {@code VARCHAR(n)} where {@code n} is the maximum
+ * number of code points. {@code n} must have a value between 1 and {@link Integer#MAX_VALUE} (both
+ * inclusive). If no length is specified, {@code n} is equal to 1.
+ */
+@PublicEvolving
+public final class VarCharType extends LogicalType {
+
+	private static final int MIN_LENGTH = 1;
+
+	private static final int MAX_LENGTH = Integer.MAX_VALUE;
+
+	private static final int DEFAULT_LENGTH = 1;
+
+	private static final String DEFAULT_FORMAT = "VARCHAR(%d)";
+
+	private static final Set<String> INPUT_OUTPUT_CONVERSION = conversionSet(
+		String.class.getName(),
+		byte[].class.getName(),
+		"org.apache.flink.table.dataformat.BinaryString");
+
+	private static final Class<?> DEFAULT_CONVERSION = String.class;
+
+	private final int length;
+
+	public VarCharType(boolean isNullable, int length) {
+		super(isNullable, LogicalTypeRoot.VARCHAR);
+		if (length < MIN_LENGTH) {
+			throw new ValidationException(
+				String.format(
+					"Variable character string length must be between %d and %d (both inclusive).",
+					MIN_LENGTH,
+					MAX_LENGTH));
+		}
+		this.length = length;
+	}
+
+	public VarCharType(int length) {
+		this(true, length);
+	}
+
+	public VarCharType() {
+		this(DEFAULT_LENGTH);
+	}
+
+	public int getLength() {
+		return length;
+	}
+
+	@Override
+	public LogicalType copy(boolean isNullable) {
+		return new VarCharType(isNullable, length);
+	}
+
+	@Override
+	public String asSerializableString() {
+		return withNullability(DEFAULT_FORMAT, length);
+	}
+
+	@Override
+	public boolean supportsInputConversion(Class<?> clazz) {
+		return INPUT_OUTPUT_CONVERSION.contains(clazz.getName());
+	}
+
+	@Override
+	public boolean supportsOutputConversion(Class<?> clazz) {
+		return INPUT_OUTPUT_CONVERSION.contains(clazz.getName());
+	}
+
+	@Override
+	public Class<?> getDefaultOutputConversion() {
+		return DEFAULT_CONVERSION;
+	}
+
+	@Override
+	public List<LogicalType> getChildren() {
+		return Collections.emptyList();
+	}
+
+	@Override
+	public <R> R accept(LogicalTypeVisitor<R> visitor) {
+		return visitor.visit(this);
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) {
+			return true;
+		}
+		if (o == null || getClass() != o.getClass()) {
+			return false;
+		}
+		if (!super.equals(o)) {
+			return false;
+		}
+		VarCharType that = (VarCharType) o;
+		return length == that.length;
+	}
+
+	@Override
+	public int hashCode() {
+		return Objects.hash(super.hashCode(), length);
+	}
+}

flink-table/flink-table-common/src/test/java/org/apache/flink/table/types/LogicalTypesTest.java

@@ -20,6 +20,7 @@
 
 import org.apache.flink.table.types.logical.CharType;
 import org.apache.flink.table.types.logical.LogicalType;
+import org.apache.flink.table.types.logical.VarCharType;
 import org.apache.flink.util.InstantiationUtil;
 
 import org.junit.Assert;
@@ -49,6 +50,18 @@ public void testCharType() {
 		);
 	}
 
+	@Test
+	public void testVarCharType() {
+		testAll(
+			new VarCharType(33),
+			"VARCHAR(33)",
+			new Class[]{String.class, byte[].class},
+			new Class[]{String.class, byte[].class},
+			new LogicalType[]{},
+			new VarCharType(12)
+		);
+	}
+
 	// --------------------------------------------------------------------------------------------
 
 	private static void testAll(