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.disk.v1.vector;
  
  import java.util.List;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.function.Function;
  
  import com.google.common.base.Preconditions;
  
  import org.agrona.collections.IntArrayList;
  import org.apache.lucene.util.RamUsageEstimator;
  
  public class VectorPostings<T>
  {
      private final List<T> postings;
      private volatile int ordinal = -1;
  
      private volatile IntArrayList rowIds;
  
      public VectorPostings(T firstKey)
      {
          // we expect that the overwhelmingly most common cardinality will be 1, so optimize for reads
          postings = new CopyOnWriteArrayList<>(List.of(firstKey));
      }
  
      /**
       * Split out from constructor only to make dealing with concurrent inserts easier for CassandraOnHeapGraph.
       * Should be called at most once per instance.
       */
      void setOrdinal(int ordinal)
      {
          assert this.ordinal == -1 : String.format("ordinal already set to %d; attempted to set to %d", this.ordinal, ordinal);
          this.ordinal = ordinal;
      }
  
      public boolean add(T key)
      {
          for (T existing : postings)
              if (existing.equals(key))
                  return false;
          postings.add(key);
          return true;
      }
  
      /**
       * @return true if current ordinal is removed by partition/range deletion.
       * Must be called after computeRowIds.
       */
      public boolean shouldAppendDeletedOrdinal()
      {
          return !postings.isEmpty() && (rowIds != null && rowIds.isEmpty());
      }
  
      /**
       * Compute the rowIds corresponding to the {@code <T>} keys in this postings list.
       */
      public void computeRowIds(Function<T, Integer> postingTransformer)
      {
          Preconditions.checkState(rowIds == null);
  
          IntArrayList ids = new IntArrayList(postings.size(), -1);
          for (T key : postings)
          {
              int rowId = postingTransformer.apply(key);
              // partition deletion and range deletion won't trigger index update. There is no row id for given key during flush
              if (rowId >= 0)
                  ids.add(rowId);
          }
  
          rowIds = ids;
      }
  
      /**
       * @return rowIds corresponding to the {@code <T>} keys in this postings list.
       * Must be called after computeRowIds.
       */
      public IntArrayList getRowIds()
      {
          Preconditions.checkNotNull(rowIds);
          return rowIds;
      }
  
      public long remove(T key)
      {
          long bytesUsed = ramBytesUsed();
          postings.remove(key);
          return bytesUsed - ramBytesUsed();
      }
  
      public long ramBytesUsed()
      {
          return emptyBytesUsed() + postings.size() * bytesPerPosting();
      }
  
      public static long emptyBytesUsed()
      {
          long REF_BYTES = RamUsageEstimator.NUM_BYTES_OBJECT_REF;
          long AH_BYTES = RamUsageEstimator.NUM_BYTES_ARRAY_HEADER;
          return Integer.BYTES + REF_BYTES + AH_BYTES;
      }
  
      // we can't do this exactly without reflection, because keys could be Long or PrimaryKey.
      // PK is larger, so we'll take that and return an upper bound.
      // we already count the float[] vector in vectorValues, so leave it out here
      public static long bytesPerPosting()
      {
          long REF_BYTES = RamUsageEstimator.NUM_BYTES_OBJECT_REF;
          return REF_BYTES
                 + 2 * Long.BYTES // hashes in PreHashedDecoratedKey
                 + REF_BYTES; // key ByteBuffer, this is used elsewhere, so we don't take the deep size
      }
  
      public int size()
      {
          return postings.size();
      }
  
      public List<T> getPostings()
      {
          return postings;
      }
  
      public boolean isEmpty()
      {
          return postings.isEmpty();
      }
  
      public int getOrdinal()
      {
          assert ordinal >= 0 : "ordinal not set";
          return ordinal;
      }
  }
  