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;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.util.Comparator;
  import java.util.List;
  import java.util.concurrent.atomic.AtomicBoolean;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import com.google.common.base.MoreObjects;
  import com.google.common.base.Objects;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.db.PartitionPosition;
  import org.apache.cassandra.db.virtual.SimpleDataSet;
  import org.apache.cassandra.dht.AbstractBounds;
  import org.apache.cassandra.index.sai.QueryContext;
  import org.apache.cassandra.index.sai.SSTableContext;
  import org.apache.cassandra.index.sai.StorageAttachedIndex;
  import org.apache.cassandra.index.sai.disk.format.Version;
  import org.apache.cassandra.index.sai.disk.v1.segment.SegmentOrdering;
  import org.apache.cassandra.index.sai.iterators.KeyRangeIterator;
  import org.apache.cassandra.index.sai.plan.Expression;
  import org.apache.cassandra.index.sai.utils.IndexIdentifier;
  import org.apache.cassandra.index.sai.utils.IndexTermType;
  import org.apache.cassandra.io.sstable.SSTableIdFactory;
  import org.apache.cassandra.io.sstable.format.SSTableReader;
  
  /**
   * A reference-counted container of a {@link SSTableReader} for each column index that:
   * <ul>
   *     <li>Manages references to the SSTable for each query</li>
   *     <li>Exposes a version agnostic searcher onto the column index</li>
   *     <li>Exposes the index metadata for the column index</li>
   * </ul>
   */
  public abstract class SSTableIndex implements SegmentOrdering, Comparable<SSTableIndex>
  {
      private static final Logger logger = LoggerFactory.getLogger(SSTableIndex.class);
  
      // sort sstable indexes by first key, then last key, then descriptor id
      public static final Comparator<SSTableIndex> COMPARATOR = Comparator.comparing((SSTableIndex s) -> s.getSSTable().getFirst())
                                                                          .thenComparing(s -> s.getSSTable().getLast())
                                                                          .thenComparing(s -> s.getSSTable().descriptor.id, SSTableIdFactory.COMPARATOR);
  
      protected final SSTableContext sstableContext;
      protected final IndexTermType indexTermType;
      protected final IndexIdentifier indexIdentifier;
  
      private final AtomicInteger references = new AtomicInteger(1);
      private final AtomicBoolean obsolete = new AtomicBoolean(false);
  
      public SSTableIndex(SSTableContext sstableContext, StorageAttachedIndex index)
      {
          // This shared copy must be closed if a subclass constructor fails.
          this.sstableContext = sstableContext.sharedCopy(); 
          this.indexTermType = index.termType();
          this.indexIdentifier = index.identifier();
      }
  
      /**
       * Returns the amount of memory occupied by the index when it is initially loaded.
       * This is the amount of data loaded into internal memory buffers by the index and
       * does include the class footprint overhead. It used by the index metrics.
       */
      public abstract long indexFileCacheSize();
  
      /**
       * Returns the number of indexed rows in the index. This comes from the index
       * metadata created when the index was written and is used by the index metrics.
       */
      public abstract long getRowCount();
  
      /**
       * Returns the minimum indexed rowId for the index. This comes from the index
       * metadata created when the index was written and is used by the index metrics.
       */
      public abstract long minSSTableRowId();
  
      /**
       * Returns the maximum indexed rowId for the index. This comes from the index
       * metadata created when the index was written and is used by the index metrics.
       */
      public abstract long maxSSTableRowId();
  
      /**
       * Returns the minimum term held in the index based on the natural sort order of
       * the index column type comparator. It comes from the index metadata created when
       * the index was written and is used by the index metrics and used in queries to
       * determine whether a term, or range or terms, exists in the index.
       */
      public abstract ByteBuffer minTerm();
  
      /**
       * Returns the maximum term held in the index based on the natural sort order of
       * the index column type comparator. It comes from the index metadata created when
       * the index was written and is used by the index metrics and used in queries to
       * determine whether a term, or range or terms, exists in the index.
       */
      public abstract ByteBuffer maxTerm();
  
      /**
       * Returns the key bounds of the index. It is created from the minimum and
       * maximum keys held in the metadata and is used to determine whether
       * sstable indexes overlap or not.
       */
      public abstract AbstractBounds<PartitionPosition> bounds();
  
      /**
       * Perform a search on the index for a single expression and keyRange.
       * <p>
       * The result is a {@link List} of {@link KeyRangeIterator} because there will
       * be a {@link KeyRangeIterator} for each segment in the index. The result
       * will never be null but may be an empty {@link List}.
       *
       * @param expression The {@link Expression} to be searched for
       * @param keyRange The {@code AbstractBounds<PartitionPosition>} defining the
       *                 token range for the search
       * @param context The {@link QueryContext} holding the per-query state
       * @return a {@link List} of {@link KeyRangeIterator}s containing the results
       * of the search
       */
      public abstract List<KeyRangeIterator> search(Expression expression,
                                                    AbstractBounds<PartitionPosition> keyRange,
                                                    QueryContext context) throws IOException;
  
      /**
       * Populates a virtual table using the index metadata owned by the index
       */
      public abstract void populateSegmentView(SimpleDataSet dataSet);
  
      protected abstract void internalRelease();
  
      /**
       * @return total size of per-column index components, in bytes
       */
      public long sizeOfPerColumnComponents()
      {
          return sstableContext.indexDescriptor.sizeOnDiskOfPerIndexComponents(indexTermType, indexIdentifier);
      }
  
      public IndexTermType getIndexTermType()
      {
          return indexTermType;
      }
  
      public IndexIdentifier getIndexIdentifier()
      {
          return indexIdentifier;
      }
  
      public SSTableContext getSSTableContext()
      {
          return sstableContext;
      }
  
      public Version getVersion()
      {
          return sstableContext.indexDescriptor.version;
      }
  
      public SSTableReader getSSTable()
      {
          return sstableContext.sstable;
      }
  
      public boolean reference()
      {
          while (true)
          {
              int n = references.get();
              if (n <= 0)
                  return false;
              if (references.compareAndSet(n, n + 1))
              {
                  return true;
              }
          }
      }
  
      public boolean isReleased()
      {
          return references.get() <= 0;
      }
  
      public void releaseQuietly()
      {
          try
          {
              release();
          }
          catch (Throwable e)
          {
              logger.error(indexIdentifier.logMessage("Failed to release index on SSTable {}"), getSSTable().descriptor, e);
          }
      }
  
      public void release()
      {
          int n = references.decrementAndGet();
  
          if (n == 0)
          {
              internalRelease();
              sstableContext.close();
  
              /*
               * When SSTable is removed, storage-attached index components will be automatically removed by LogTransaction.
               * We only remove index components explicitly in case of index corruption or index rebuild.
               */
              if (obsolete.get())
              {
                  sstableContext.indexDescriptor.deleteColumnIndex(indexTermType, indexIdentifier);
              }
          }
      }
  
      public void markObsolete()
      {
          obsolete.getAndSet(true);
          release();
      }
  
      @Override
      public boolean equals(Object o)
      {
          if (this == o) return true;
          if (o == null || getClass() != o.getClass()) return false;
          SSTableIndex other = (SSTableIndex)o;
          return Objects.equal(sstableContext, other.sstableContext) &&
                 Objects.equal(indexTermType, other.indexTermType) &&
                 Objects.equal(indexIdentifier, other.indexIdentifier);
      }
  
      @Override
      public int hashCode()
      {
          return Objects.hashCode(sstableContext, indexTermType, indexIdentifier);
      }
  
      @Override
      public String toString()
      {
          return MoreObjects.toStringHelper(this)
                            .add("column", indexTermType.columnName())
                            .add("sstable", sstableContext.sstable.descriptor)
                            .add("minTerm", indexTermType.asString(minTerm()))
                            .add("maxTerm", indexTermType.asString(maxTerm()))
                            .add("totalRows", sstableContext.sstable.getTotalRows())
                            .toString();
      }
  
      @Override
      public int compareTo(SSTableIndex index)
      {
          // SSTableReader is truly unique for comparison which is relied on in IntervalTree
          return getSSTable().compareTo(index.getSSTable());
      }
  }
  