maedhroz commented on code in PR #2267: URL: https://github.com/apache/cassandra/pull/2267#discussion_r1183084470
########## src/java/org/apache/cassandra/io/sstable/format/bti/SSTableReversedIterator.java: ########## @@ -0,0 +1,293 @@ +/* + * 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.io.sstable.format.bti; + +import java.io.IOException; +import java.util.NoSuchElementException; + +import com.carrotsearch.hppc.LongStack; +import org.apache.cassandra.db.ClusteringBound; +import org.apache.cassandra.db.ClusteringComparator; +import org.apache.cassandra.db.DecoratedKey; +import org.apache.cassandra.db.Slice; +import org.apache.cassandra.db.Slices; +import org.apache.cassandra.db.UnfilteredValidation; +import org.apache.cassandra.db.filter.ColumnFilter; +import org.apache.cassandra.db.rows.RangeTombstoneBoundMarker; +import org.apache.cassandra.db.rows.RangeTombstoneMarker; +import org.apache.cassandra.db.rows.Unfiltered; +import org.apache.cassandra.io.sstable.AbstractRowIndexEntry; +import org.apache.cassandra.io.sstable.AbstractSSTableIterator; +import org.apache.cassandra.io.sstable.format.bti.RowIndexReader.IndexInfo; +import org.apache.cassandra.io.util.FileDataInput; +import org.apache.cassandra.io.util.FileHandle; + +/** + * Unfiltered row iterator over a BTI SSTable that returns rows in reverse order. + */ +class SSTableReversedIterator extends AbstractSSTableIterator<TrieIndexEntry> +{ + /** + * The index of the slice being processed. + */ + private int slice; + + public SSTableReversedIterator(BtiTableReader sstable, + FileDataInput file, + DecoratedKey key, + TrieIndexEntry indexEntry, + Slices slices, + ColumnFilter columns, + FileHandle ifile) + { + super(sstable, file, key, indexEntry, slices, columns, ifile); + } + + protected Reader createReaderInternal(TrieIndexEntry indexEntry, FileDataInput file, boolean shouldCloseFile) + { + if (indexEntry.isIndexed()) + return new ReverseIndexedReader(indexEntry, file, shouldCloseFile); + else + return new ReverseReader(file, shouldCloseFile); + } + + public boolean isReverseOrder() + { + return true; + } + + protected int nextSliceIndex() + { + int next = slice; + slice++; + return slices.size() - (next + 1); + } + + protected boolean hasMoreSlices() + { + return slice < slices.size(); + } + + /** + * Reverse iteration is performed by going through an index block (or the whole partition if not indexed) forwards + * and storing the positions of each entry that falls within the slice in a stack. Reverse iteration then pops out + * positions and reads the entries. + * <p> + * Note: The earlier version of this was constructing an in-memory view of the block instead, which gives better + * performance on bigger queries and index blocks (due to not having to read disk again). With the lower + * granularity of the tries it makes better sense to store as little as possible as the beginning of the block + * should very rarely be in other page/chunk cache locations. This has the benefit of being able to answer small + * queries (esp. LIMIT 1) faster and with less GC churn. + */ + private class ReverseReader extends AbstractReader + { + final LongStack rowOffsets = new LongStack(); + RangeTombstoneMarker blockOpenMarker, blockCloseMarker; + private Unfiltered next = null; + private boolean foundLessThan; + private long startPos = -1; + + private ReverseReader(FileDataInput file, boolean shouldCloseFile) + { + super(file, shouldCloseFile); + } + + public void setForSlice(Slice slice) throws IOException Review Comment: nit: `@Override` ########## src/java/org/apache/cassandra/io/sstable/format/bti/SSTableReversedIterator.java: ########## @@ -0,0 +1,293 @@ +/* + * 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.io.sstable.format.bti; + +import java.io.IOException; +import java.util.NoSuchElementException; + +import com.carrotsearch.hppc.LongStack; +import org.apache.cassandra.db.ClusteringBound; +import org.apache.cassandra.db.ClusteringComparator; +import org.apache.cassandra.db.DecoratedKey; +import org.apache.cassandra.db.Slice; +import org.apache.cassandra.db.Slices; +import org.apache.cassandra.db.UnfilteredValidation; +import org.apache.cassandra.db.filter.ColumnFilter; +import org.apache.cassandra.db.rows.RangeTombstoneBoundMarker; +import org.apache.cassandra.db.rows.RangeTombstoneMarker; +import org.apache.cassandra.db.rows.Unfiltered; +import org.apache.cassandra.io.sstable.AbstractRowIndexEntry; +import org.apache.cassandra.io.sstable.AbstractSSTableIterator; +import org.apache.cassandra.io.sstable.format.bti.RowIndexReader.IndexInfo; +import org.apache.cassandra.io.util.FileDataInput; +import org.apache.cassandra.io.util.FileHandle; + +/** + * Unfiltered row iterator over a BTI SSTable that returns rows in reverse order. + */ +class SSTableReversedIterator extends AbstractSSTableIterator<TrieIndexEntry> +{ + /** + * The index of the slice being processed. + */ + private int slice; + + public SSTableReversedIterator(BtiTableReader sstable, + FileDataInput file, + DecoratedKey key, + TrieIndexEntry indexEntry, + Slices slices, + ColumnFilter columns, + FileHandle ifile) + { + super(sstable, file, key, indexEntry, slices, columns, ifile); + } + + protected Reader createReaderInternal(TrieIndexEntry indexEntry, FileDataInput file, boolean shouldCloseFile) + { + if (indexEntry.isIndexed()) + return new ReverseIndexedReader(indexEntry, file, shouldCloseFile); + else + return new ReverseReader(file, shouldCloseFile); + } + + public boolean isReverseOrder() + { + return true; + } + + protected int nextSliceIndex() + { + int next = slice; + slice++; + return slices.size() - (next + 1); + } + + protected boolean hasMoreSlices() + { + return slice < slices.size(); + } + + /** + * Reverse iteration is performed by going through an index block (or the whole partition if not indexed) forwards + * and storing the positions of each entry that falls within the slice in a stack. Reverse iteration then pops out + * positions and reads the entries. + * <p> + * Note: The earlier version of this was constructing an in-memory view of the block instead, which gives better + * performance on bigger queries and index blocks (due to not having to read disk again). With the lower + * granularity of the tries it makes better sense to store as little as possible as the beginning of the block + * should very rarely be in other page/chunk cache locations. This has the benefit of being able to answer small + * queries (esp. LIMIT 1) faster and with less GC churn. + */ + private class ReverseReader extends AbstractReader + { + final LongStack rowOffsets = new LongStack(); + RangeTombstoneMarker blockOpenMarker, blockCloseMarker; + private Unfiltered next = null; + private boolean foundLessThan; + private long startPos = -1; + + private ReverseReader(FileDataInput file, boolean shouldCloseFile) + { + super(file, shouldCloseFile); + } + + public void setForSlice(Slice slice) throws IOException + { + // read full row and filter + if (startPos == -1) + startPos = file.getFilePointer(); + else + seekToPosition(startPos); + + fillOffsets(slice, true, true, Long.MAX_VALUE); + } + + protected boolean hasNextInternal() throws IOException Review Comment: nit: `@Override` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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