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.jdbc;
  
  import org.apache.calcite.linq4j.Enumerator;
  import org.apache.calcite.schema.Schema;
  import org.apache.calcite.schema.Table;
  import org.apache.calcite.schema.impl.AbstractSchema;
  
  import com.google.common.collect.ImmutableMap;
  
  import java.sql.SQLException;
  import java.util.Map;
  
  import static org.apache.calcite.avatica.MetaImpl.MetaColumn;
  import static org.apache.calcite.avatica.MetaImpl.MetaTable;
  
  /** Schema that contains metadata tables such as "TABLES" and "COLUMNS". */
  class MetadataSchema extends AbstractSchema {
    private static final Map<String, Table> TABLE_MAP =
        ImmutableMap.of(
            "COLUMNS",
            new CalciteMetaImpl.MetadataTable<MetaColumn>(MetaColumn.class) {
              @Override public Enumerator<MetaColumn> enumerator(
                  final CalciteMetaImpl meta) {
                final String catalog;
                try {
                  catalog = meta.getConnection().getCatalog();
                } catch (SQLException e) {
                  throw new RuntimeException(e);
                }
                return meta.tables(catalog)
                    .selectMany(meta::columns).enumerator();
              }
            },
            "TABLES",
            new CalciteMetaImpl.MetadataTable<MetaTable>(MetaTable.class) {
              @Override public Enumerator<MetaTable> enumerator(CalciteMetaImpl meta) {
                final String catalog;
                try {
                  catalog = meta.getConnection().getCatalog();
                } catch (SQLException e) {
                  throw new RuntimeException(e);
                }
                return meta.tables(catalog).enumerator();
              }
            });
  
    public static final Schema INSTANCE = new MetadataSchema();
  
    /** Creates the data dictionary, also called the information schema. It is a
     * schema called "metadata" that contains tables "TABLES", "COLUMNS" etc. */
    private MetadataSchema() {}
  
    @Override protected Map<String, Table> getTableMap() {
      return TABLE_MAP;
    }
  }
  