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.cassandra.cql3.selection;
  
  import java.util.List;
  import java.util.Set;
  
  import org.apache.cassandra.db.filter.ColumnFilter;
  import org.apache.cassandra.schema.ColumnMetadata;
  import org.apache.cassandra.schema.TableMetadata;
  
  /**
   * Factory for {@code ColumnFilter} instances.
   * <p>This class is used to abstract the fact that depending on the selection clause the {@code ColumnFilter} instances
   * can be computed at prepartion time (if all the requested columns are known) or must be computed at execution time.</p>
   */
  abstract class ColumnFilterFactory
  {
      /**
       * Returns the {@code ColumnFilter} instance corresponding to the specified selectors.
       * @param selectors the selectors for which the {@code ColumnFilter} must be created.
       * @return the {@code ColumnFilter} instance corresponding to the specified selectors
       */
      abstract ColumnFilter newInstance(List<Selector> selectors);
  
      public static ColumnFilterFactory wildcard(TableMetadata table)
      {
          return new PrecomputedColumnFilter(ColumnFilter.all(table));
      }
  
      public static ColumnFilterFactory fromColumns(TableMetadata table,
                                                    List<ColumnMetadata> selectedColumns,
                                                    Set<ColumnMetadata> orderingColumns,
                                                    Set<ColumnMetadata> nonPKRestrictedColumns,
                                                    boolean returnStaticContentOnPartitionWithNoRows)
      {
          ColumnFilter.Builder builder = ColumnFilter.allRegularColumnsBuilder(table, returnStaticContentOnPartitionWithNoRows);
          builder.addAll(selectedColumns);
          builder.addAll(orderingColumns);
          // we'll also need to fetch any column on which we have a restriction (so we can apply said restriction)
          builder.addAll(nonPKRestrictedColumns);
          return new PrecomputedColumnFilter(builder.build());
      }
  
      /**
       * Creates a new {@code ColumnFilterFactory} instance from the specified {@code SelectorFactories}.
       *
       * @param table the table metadata
       * @param factories the {@code SelectorFactories}
       * @param orderingColumns the columns used for ordering
       * @param nonPKRestrictedColumns the non primary key columns that have been restricted in the WHERE clause
       * @param returnStaticContentOnPartitionWithNoRows {@code true} if the query will return the static content when the
       * partition has no rows, {@code false} otherwise.
       * @return a new {@code ColumnFilterFactory} instance
       */
      public static ColumnFilterFactory fromSelectorFactories(TableMetadata table,
                                                              SelectorFactories factories,
                                                              Set<ColumnMetadata> orderingColumns,
                                                              Set<ColumnMetadata> nonPKRestrictedColumns,
                                                              boolean returnStaticContentOnPartitionWithNoRows)
      {
          if (factories.areAllFetchedColumnsKnown())
          {
              ColumnFilter.Builder builder = ColumnFilter.allRegularColumnsBuilder(table, returnStaticContentOnPartitionWithNoRows);
              factories.addFetchedColumns(builder);
              builder.addAll(orderingColumns);
              // we'll also need to fetch any column on which we have a restriction (so we can apply said restriction)
              builder.addAll(nonPKRestrictedColumns);
              return new PrecomputedColumnFilter(builder.build());
          }
  
          return new OnRequestColumnFilterFactory(table, nonPKRestrictedColumns, returnStaticContentOnPartitionWithNoRows);
      }
  
      /**
       * A factory that always return the same pre-computed {@code ColumnFilter}.
       */
      private static class PrecomputedColumnFilter extends ColumnFilterFactory
      {
          /**
           * The precomputed {@code ColumnFilter}
           */
          private final ColumnFilter columnFilter;
  
          public PrecomputedColumnFilter(ColumnFilter columnFilter)
          {
              this.columnFilter = columnFilter;
          }
  
          @Override
          public ColumnFilter newInstance(List<Selector> selectors)
          {
              return columnFilter;
          }
      }
  
      /**
       * A factory that will computed the {@code ColumnFilter} on request.
       */
      private static class OnRequestColumnFilterFactory extends ColumnFilterFactory
      {
          private final TableMetadata table;
          private final Set<ColumnMetadata> nonPKRestrictedColumns;
          private final boolean returnStaticContentOnPartitionWithNoRows;
  
          public OnRequestColumnFilterFactory(TableMetadata table,
                                              Set<ColumnMetadata> nonPKRestrictedColumns,
                                              boolean returnStaticContentOnPartitionWithNoRows)
          {
              this.table = table;
              this.nonPKRestrictedColumns = nonPKRestrictedColumns;
              this.returnStaticContentOnPartitionWithNoRows = returnStaticContentOnPartitionWithNoRows;
          }
  
          @Override
          public ColumnFilter newInstance(List<Selector> selectors)
          {
              ColumnFilter.Builder builder = ColumnFilter.allRegularColumnsBuilder(table, returnStaticContentOnPartitionWithNoRows);
              for (int i = 0, m = selectors.size(); i < m; i++)
                  selectors.get(i).addFetchedColumns(builder);
  
              // we'll also need to fetch any column on which we have a restriction (so we can apply said restriction)
              builder.addAll(nonPKRestrictedColumns);
              return builder.build();
          }
      }
  }
  