content: /*
   * 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.calcite.sql.ddl;
  
  import org.apache.calcite.sql.SqlCall;
  import org.apache.calcite.sql.SqlIdentifier;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql.SqlOperator;
  import org.apache.calcite.sql.SqlSpecialOperator;
  import org.apache.calcite.sql.SqlWriter;
  import org.apache.calcite.sql.parser.SqlParserPos;
  import org.apache.calcite.util.ImmutableNullableList;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  /**
   * Parse tree for {@code UNIQUE}, {@code PRIMARY KEY} constraints.
   *
   * <p>And {@code FOREIGN KEY}, when we support it.
   */
  public class SqlCheckConstraint extends SqlCall {
    private static final SqlSpecialOperator OPERATOR =
        new SqlSpecialOperator("CHECK", SqlKind.CHECK);
  
    private final @Nullable SqlIdentifier name;
    private final SqlNode expression;
  
    /** Creates a SqlCheckConstraint; use {@link SqlDdlNodes#check}. */
    SqlCheckConstraint(SqlParserPos pos, @Nullable SqlIdentifier name,
        SqlNode expression) {
      super(pos);
      this.name = name; // may be null
      this.expression = expression;
    }
  
    @Override public SqlOperator getOperator() {
      return OPERATOR;
    }
  
    @SuppressWarnings("nullness")
    @Override public List<SqlNode> getOperandList() {
      return ImmutableNullableList.of(name, expression);
    }
  
    @Override public void unparse(SqlWriter writer, int leftPrec, int rightPrec) {
      if (name != null) {
        writer.keyword("CONSTRAINT");
        name.unparse(writer, 0, 0);
      }
      writer.keyword("CHECK");
      if (writer.isAlwaysUseParentheses()) {
        expression.unparse(writer, 0, 0);
      } else {
        writer.sep("(");
        expression.unparse(writer, 0, 0);
        writer.sep(")");
      }
    }
  }
  