exec/java-exec/src/main/java/org/apache/drill/exec/store/AbstractSchema.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.drill.exec.store;

import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Set;

import net.hydromatic.linq4j.expressions.DefaultExpression;
import net.hydromatic.linq4j.expressions.Expression;
import net.hydromatic.optiq.Function;
import net.hydromatic.optiq.Schema;
import net.hydromatic.optiq.SchemaPlus;
import net.hydromatic.optiq.Table;

import org.apache.drill.exec.planner.logical.CreateTableEntry;

import com.google.common.base.Joiner;
import com.google.common.collect.Lists;

public abstract class AbstractSchema implements Schema{
  static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(AbstractSchema.class);

  protected final List<String> schemaPath;
  protected final String name;
  private static final Expression EXPRESSION = new DefaultExpression(Object.class);

  public AbstractSchema(List<String> parentSchemaPath, String name) {
    schemaPath = Lists.newArrayList();
    schemaPath.addAll(parentSchemaPath);
    schemaPath.add(name);
    this.name = name;
  }

  public String getName() {
    return name;
  }

  public List<String> getSchemaPath() {
    return schemaPath;
  }

  public String getFullSchemaName() {
    return Joiner.on(".").join(schemaPath);
  }

  public abstract String getTypeName();

  /**
   * The schema can be a top level schema which doesn't have its own tables, but refers
   * to one of the default sub schemas for table look up.
   *
   * Default implementation returns itself.
   *
   * Ex. "dfs" schema refers to the tables in "default" workspace when querying for
   * tables in "dfs" schema.
   *
   * @return Return the default schema where tables are created or retrieved from.
   */
  public AbstractSchema getDefaultSchema() {
    return this;
  }

  public CreateTableEntry createNewTable(String tableName) {
    throw new UnsupportedOperationException("New tables are not allowed in this schema");
  }

  public boolean showInInformationSchema() {
    return true;
  }

  @Override
  public Collection<Function> getFunctions(String name) {
    return Collections.emptyList();
  }

  @Override
  public Set<String> getFunctionNames() {
    return Collections.emptySet();
  }

  @Override
  public Schema getSubSchema(String name) {
    return null;
  }

  @Override
  public Set<String> getSubSchemaNames() {
    return Collections.emptySet();
  }

  @Override
  public boolean isMutable() {
    return false;
  }

  @Override
  public Table getTable(String name){
    return null;
  }

  @Override
  public Set<String> getTableNames() {
    return Collections.emptySet();
  }

  @Override
  public Expression getExpression(SchemaPlus parentSchema, String name) {
    return EXPRESSION;
  }

  @Override
  public boolean contentsHaveChangedSince(long lastCheck, long now) {
    return true;
  }


}