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.adapter.jdbc;
  
  import org.apache.calcite.DataContext;
  import org.apache.calcite.linq4j.tree.Expression;
  import org.apache.calcite.linq4j.tree.Expressions;
  import org.apache.calcite.schema.Schema;
  import org.apache.calcite.schema.SchemaPlus;
  import org.apache.calcite.schema.Schemas;
  import org.apache.calcite.schema.Table;
  import org.apache.calcite.schema.Wrapper;
  import org.apache.calcite.schema.lookup.IgnoreCaseLookup;
  import org.apache.calcite.schema.lookup.LikePattern;
  import org.apache.calcite.schema.lookup.LoadingCacheLookup;
  import org.apache.calcite.schema.lookup.Lookup;
  import org.apache.calcite.sql.SqlDialect;
  import org.apache.calcite.sql.SqlDialectFactory;
  import org.apache.calcite.sql.SqlDialectFactoryImpl;
  import org.apache.calcite.util.BuiltInMethod;
  
  import com.google.common.base.Suppliers;
  import com.google.common.collect.ImmutableSet;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.sql.Connection;
  import java.sql.ResultSet;
  import java.sql.SQLException;
  import java.util.Optional;
  import java.util.Set;
  import java.util.function.Supplier;
  import javax.sql.DataSource;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Schema based upon a JDBC catalog (database).
   *
   * <p>This schema does not directly contain tables, but contains a sub-schema
   * for each schema in the catalog in the back-end. Each of those sub-schemas is
   * an instance of {@link JdbcSchema}.
   *
   * <p>This schema is lazy: it does not compute the list of schema names until
   * the first call to {@link #subSchemas()} and {@link Lookup#get(String)}. Then it creates a
   * {@link JdbcSchema} for this schema name. Each JdbcSchema will populate its
   * tables on demand.
   */
  public class JdbcCatalogSchema extends JdbcBaseSchema implements Wrapper {
    final DataSource dataSource;
    public final SqlDialect dialect;
    final JdbcConvention convention;
    final String catalog;
    private final Lookup<JdbcSchema> subSchemas;
  
    /** default schema name, lazily initialized. */
    @SuppressWarnings({"method.invocation.invalid", "Convert2MethodRef"})
    private final Supplier<Optional<String>> defaultSchemaName =
        Suppliers.memoize(() -> Optional.ofNullable(computeDefaultSchemaName()));
  
    /** Creates a JdbcCatalogSchema. */
    public JdbcCatalogSchema(DataSource dataSource, SqlDialect dialect,
        JdbcConvention convention, String catalog) {
      this.dataSource = requireNonNull(dataSource, "dataSource");
      this.dialect = requireNonNull(dialect, "dialect");
      this.convention = requireNonNull(convention, "convention");
      this.catalog = catalog;
      this.subSchemas = new LoadingCacheLookup<>(new IgnoreCaseLookup<JdbcSchema>() {
        @Override public @Nullable JdbcSchema get(String name) {
          try (Connection connection = dataSource.getConnection();
              ResultSet resultSet =
                  connection.getMetaData().getSchemas(catalog, name)) {
            while (resultSet.next()) {
              final String schemaName =
                  requireNonNull(resultSet.getString(1),
                      "got null schemaName from the database");
              return new JdbcSchema(dataSource, dialect, convention, catalog, schemaName);
            }
          } catch (SQLException e) {
            throw new RuntimeException(e);
          }
          return null;
        }
  
        @Override public Set<String> getNames(LikePattern pattern) {
          final ImmutableSet.Builder<String> builder =
              ImmutableSet.builder();
          try (Connection connection = dataSource.getConnection();
              ResultSet resultSet =
                  connection.getMetaData().getSchemas(catalog, pattern.pattern)) {
            while (resultSet.next()) {
              builder.add(
                  requireNonNull(resultSet.getString(1),
                      "got null schemaName from the database"));
            }
          } catch (SQLException e) {
            throw new RuntimeException(e);
          }
          return builder.build();
        }
      });
    }
  
    public static JdbcCatalogSchema create(
        @Nullable SchemaPlus parentSchema,
        String name,
        DataSource dataSource,
        String catalog) {
      return create(parentSchema, name, dataSource,
          SqlDialectFactoryImpl.INSTANCE, catalog);
    }
  
    public static JdbcCatalogSchema create(
        @Nullable SchemaPlus parentSchema,
        String name,
        DataSource dataSource,
        SqlDialectFactory dialectFactory,
        String catalog) {
      final Expression expression =
          parentSchema != null
              ? Schemas.subSchemaExpression(parentSchema, name,
                  JdbcCatalogSchema.class)
              : Expressions.call(DataContext.ROOT,
                  BuiltInMethod.DATA_CONTEXT_GET_ROOT_SCHEMA.method);
      final SqlDialect dialect =
          JdbcSchema.createDialect(dialectFactory, dataSource);
      final JdbcConvention convention =
          JdbcConvention.of(dialect, expression, name);
      return new JdbcCatalogSchema(dataSource, dialect, convention, catalog);
    }
  
    @Override public Lookup<Table> tables() {
      return Lookup.empty();
    }
  
    @Override public Lookup<? extends Schema> subSchemas() {
      return subSchemas;
    }
  
    private @Nullable String computeDefaultSchemaName() {
      try (Connection connection = dataSource.getConnection()) {
        return connection.getSchema();
      } catch (SQLException e) {
        throw new RuntimeException(e);
      }
    }
  
    /** Returns the name of the default sub-schema. */
    public @Nullable String getDefaultSubSchemaName() {
      return defaultSchemaName.get().orElse(null);
    }
  
    /** Returns the data source. */
    public DataSource getDataSource() {
      return dataSource;
    }
  
  
    @Override public <T extends Object> @Nullable T unwrap(Class<T> clazz) {
      if (clazz.isInstance(this)) {
        return clazz.cast(this);
      }
      if (clazz == DataSource.class) {
        return clazz.cast(getDataSource());
      }
      return null;
    }
  }
  