core/src/main/java/org/apache/calcite/schema/ModifiableView.java

/*
 * 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.schema;

import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rex.RexBuilder;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.util.ImmutableIntList;

/**
 * A modifiable view onto {@link ModifiableTable}.
 *
 * <p>It describes how its columns map onto the underlying table's columns,
 * and any constraints that incoming rows must satisfy.
 *
 * <p>For example, given
 *
 * <blockquote><pre>
 *   CREATE TABLE emps (empno INTEGER, gender VARCHAR(1), deptno INTEGER);
 *   CREATE VIEW female_emps AS
 *     SELECT empno, deptno FROM emps WHERE gender = 'F';
 * </pre></blockquote>
 *
 * <p>constraint is {@code $1 = 'F'}
 * and column mapping is {@code [0, 2]}.
 *
 * <p>NOTE: The current API is inefficient and experimental. It will change
 * without notice.
 */
public interface ModifiableView extends Table {
  /** Returns a constraint that each candidate row must satisfy.
   *
   * <p>Never null; if there is no constraint, returns "true".
   *
   * @param rexBuilder Rex builder
   * @param tableRowType Row type of the table that this view maps onto
   */
  RexNode getConstraint(RexBuilder rexBuilder, RelDataType tableRowType);

  /** Returns the column mapping onto another table.
   *
   * <p>{@code mapping[i]} contains the column of the underlying table that the
   * {@code i}th column of the view comes from, or -1 if it is based on an
   * expression.
   */
  ImmutableIntList getColumnMapping();

  /** Returns the underlying table. */
  Table getTable();

  /** Returns the full path of the underlying table. */
  Path getTablePath();
}