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.index.sai.plan;
  
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.TimeUnit;
  import java.util.function.Function;
  import javax.annotation.Nullable;
  
  import com.google.common.collect.ImmutableSet;
  
  import org.apache.cassandra.config.DatabaseDescriptor;
  import org.apache.cassandra.db.ColumnFamilyStore;
  import org.apache.cassandra.db.ReadCommand;
  import org.apache.cassandra.db.filter.RowFilter;
  import org.apache.cassandra.db.partitions.PartitionIterator;
  import org.apache.cassandra.exceptions.InvalidRequestException;
  import org.apache.cassandra.index.Index;
  import org.apache.cassandra.index.sai.StorageAttachedIndex;
  import org.apache.cassandra.index.sai.metrics.TableQueryMetrics;
  import org.apache.cassandra.schema.TableMetadata;
  
  public class StorageAttachedIndexQueryPlan implements Index.QueryPlan
  {
      public static final String UNSUPPORTED_NON_STRICT_OPERATOR =
              "Operator %s is only supported in intersections for reads that do not require replica reconciliation.";
  
      private final ColumnFamilyStore cfs;
      private final TableQueryMetrics queryMetrics;
      private final RowFilter postIndexFilter;
      private final RowFilter indexFilter;
      private final Set<Index> indexes;
      private final boolean isTopK;
  
      private StorageAttachedIndexQueryPlan(ColumnFamilyStore cfs,
                                            TableQueryMetrics queryMetrics,
                                            RowFilter postIndexFilter,
                                            RowFilter indexFilter,
                                            ImmutableSet<Index> indexes)
      {
          this.cfs = cfs;
          this.queryMetrics = queryMetrics;
          this.postIndexFilter = postIndexFilter;
          this.indexFilter = indexFilter;
          this.indexes = indexes;
          this.isTopK = indexes.stream().anyMatch(i -> i instanceof StorageAttachedIndex && ((StorageAttachedIndex) i).termType().isVector());
      }
  
      @Nullable
      public static StorageAttachedIndexQueryPlan create(ColumnFamilyStore cfs,
                                                         TableQueryMetrics queryMetrics,
                                                         Set<StorageAttachedIndex> indexes,
                                                         RowFilter filter)
      {
          ImmutableSet.Builder<Index> selectedIndexesBuilder = ImmutableSet.builder();
  
          RowFilter indexFilter = filter;
          RowFilter postIndexFilter = filter;
  
          for (RowFilter.Expression expression : filter)
          {
              // We ignore any expressions here (user-defined expressions and SAI unsupported operators) where we don't have a way to
              // translate their #isSatifiedBy method, they will be included in the filter returned by 
              // QueryPlan#postIndexQueryFilter(). If strict filtering is not allowed, we must reject the query until the
              // expression(s) in question are compatible with #isSatifiedBy.
              //
              // Note: For both the pre- and post-filters we need to check that the expression exists before removing it
              // because the without method assert if the expression doesn't exist. This can be the case if we are given
              // a duplicate expression - a = 1 and a = 1. The without method removes all instances of the expression.
              if (!Expression.supportsOperator(expression.operator()) || expression.isUserDefined())
              {
                  if (!filter.isStrict())
                      throw new InvalidRequestException(String.format(UNSUPPORTED_NON_STRICT_OPERATOR, expression.operator()));
  
                  if (indexFilter.getExpressions().contains(expression))
                      indexFilter = indexFilter.without(expression);
                  continue;
              }
  
              if (postIndexFilter.getExpressions().contains(expression))
                  postIndexFilter = postIndexFilter.without(expression);
  
              for (StorageAttachedIndex index : indexes)
              {
                  if (index.supportsExpression(expression) && !filter.indexHints.excludes(index))
                  {
                      selectedIndexesBuilder.add(index);
                  }
              }
          }
  
          ImmutableSet<Index> selectedIndexes = selectedIndexesBuilder.build();
          if (selectedIndexes.isEmpty())
              return null;
  
          return new StorageAttachedIndexQueryPlan(cfs, queryMetrics, postIndexFilter, indexFilter, selectedIndexes);
      }
  
      @Override
      public Set<Index> getIndexes()
      {
          return indexes;
      }
  
      @Override
      public long getEstimatedResultRows()
      {
          return DatabaseDescriptor.getPrioritizeSAIOverLegacyIndex() ? Long.MIN_VALUE : Long.MAX_VALUE;
      }
  
      @Override
      public boolean shouldEstimateInitialConcurrency()
      {
          return false;
      }
  
      @Override
      public Index.Searcher searcherFor(ReadCommand command)
      {
          return new StorageAttachedIndexSearcher(cfs,
                                                  queryMetrics,
                                                  command,
                                                  indexFilter,
                                                  DatabaseDescriptor.getRangeRpcTimeout(TimeUnit.MILLISECONDS));
      }
  
      /**
       * Called on coordinator after merging replica responses before returning to client
       */
      @Override
      public Function<PartitionIterator, PartitionIterator> postProcessor(ReadCommand command)
      {
          if (!isTopK())
              return partitions -> partitions;
  
          // in case of top-k query, filter out rows that are not actually global top-K
          return partitions -> (PartitionIterator) new VectorTopKProcessor(command).filter(partitions);
      }
  
      /**
       * @return a filter with all the expressions that are user-defined or for a non-indexed partition key column
       * <p>
       * (currently index on partition columns is not supported, see {@link StorageAttachedIndex#validateOptions(Map, TableMetadata)})
       */
      @Override
      public RowFilter postIndexQueryFilter()
      {
          return postIndexFilter;
      }
  
      @Override
      public boolean isTopK()
      {
          return isTopK;
      }
  }
  