| /* |
| * 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.db.columniterator; |
| |
| import java.io.IOException; |
| import java.util.*; |
| |
| import org.apache.cassandra.db.*; |
| import org.apache.cassandra.db.filter.ColumnFilter; |
| import org.apache.cassandra.db.partitions.ImmutableBTreePartition; |
| import org.apache.cassandra.db.rows.*; |
| import org.apache.cassandra.io.sstable.format.SSTableReader; |
| import org.apache.cassandra.io.util.FileDataInput; |
| import org.apache.cassandra.io.util.FileHandle; |
| import org.apache.cassandra.schema.TableMetadata; |
| import org.apache.cassandra.utils.AbstractIterator; |
| import org.apache.cassandra.utils.btree.BTree; |
| |
| /** |
| * A Cell Iterator in reversed clustering order over SSTable |
| */ |
| public class SSTableReversedIterator extends AbstractSSTableIterator |
| { |
| /** |
| * The index of the slice being processed. |
| */ |
| private int slice; |
| |
| public SSTableReversedIterator(SSTableReader sstable, |
| FileDataInput file, |
| DecoratedKey key, |
| RowIndexEntry indexEntry, |
| Slices slices, |
| ColumnFilter columns, |
| FileHandle ifile) |
| { |
| super(sstable, file, key, indexEntry, slices, columns, ifile); |
| } |
| |
| protected Reader createReaderInternal(RowIndexEntry indexEntry, FileDataInput file, boolean shouldCloseFile) |
| { |
| return indexEntry.isIndexed() |
| ? new ReverseIndexedReader(indexEntry, file, shouldCloseFile) |
| : 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(); |
| } |
| |
| private class ReverseReader extends Reader |
| { |
| protected ReusablePartitionData buffer; |
| protected Iterator<Unfiltered> iterator; |
| |
| // Set in loadFromDisk () and used in setIterator to handle range tombstone extending on multiple index block. See |
| // loadFromDisk for details. Note that those are always false for non-indexed readers. |
| protected boolean skipFirstIteratedItem; |
| protected boolean skipLastIteratedItem; |
| |
| private ReverseReader(FileDataInput file, boolean shouldCloseFile) |
| { |
| super(file, shouldCloseFile); |
| } |
| |
| protected ReusablePartitionData createBuffer(int blocksCount) |
| { |
| int estimatedRowCount = 16; |
| int columnCount = metadata().regularColumns().size(); |
| if (columnCount == 0 || metadata().clusteringColumns().isEmpty()) |
| { |
| estimatedRowCount = 1; |
| } |
| else |
| { |
| try |
| { |
| // To avoid wasted resizing we guess-estimate the number of rows we're likely to read. For that |
| // we use the stats on the number of rows per partition for that sstable. |
| // FIXME: so far we only keep stats on cells, so to get a rough estimate on the number of rows, |
| // we divide by the number of regular columns the table has. We should fix once we collect the |
| // stats on rows |
| int estimatedRowsPerPartition = (int)(sstable.getEstimatedCellPerPartitionCount().percentile(0.75) / columnCount); |
| estimatedRowCount = Math.max(estimatedRowsPerPartition / blocksCount, 1); |
| } |
| catch (IllegalStateException e) |
| { |
| // The EstimatedHistogram mean() method can throw this (if it overflows). While such overflow |
| // shouldn't happen, it's not worth taking the risk of letting the exception bubble up. |
| } |
| } |
| return new ReusablePartitionData(metadata(), partitionKey(), columns(), estimatedRowCount); |
| } |
| |
| public void setForSlice(Slice slice) throws IOException |
| { |
| // If we have read the data, just create the iterator for the slice. Otherwise, read the data. |
| if (buffer == null) |
| { |
| buffer = createBuffer(1); |
| // Note that we can reuse that buffer between slices (we could alternatively re-read from disk |
| // every time, but that feels more wasteful) so we want to include everything from the beginning. |
| // We can stop at the slice end however since any following slice will be before that. |
| loadFromDisk(null, slice.end(), false, false); |
| } |
| setIterator(slice); |
| } |
| |
| protected void setIterator(Slice slice) |
| { |
| assert buffer != null; |
| iterator = buffer.built.unfilteredIterator(columns, Slices.with(metadata().comparator, slice), true); |
| |
| if (!iterator.hasNext()) |
| return; |
| |
| if (skipFirstIteratedItem) |
| iterator.next(); |
| |
| if (skipLastIteratedItem) |
| iterator = new SkipLastIterator(iterator); |
| } |
| |
| protected boolean hasNextInternal() throws IOException |
| { |
| // If we've never called setForSlice, we're reading everything |
| if (iterator == null) |
| setForSlice(Slice.ALL); |
| |
| return iterator.hasNext(); |
| } |
| |
| protected Unfiltered nextInternal() throws IOException |
| { |
| if (!hasNext()) |
| throw new NoSuchElementException(); |
| return iterator.next(); |
| } |
| |
| protected boolean stopReadingDisk() throws IOException |
| { |
| return false; |
| } |
| |
| // Reads the unfiltered from disk and load them into the reader buffer. It stops reading when either the partition |
| // is fully read, or when stopReadingDisk() returns true. |
| protected void loadFromDisk(ClusteringBound<?> start, |
| ClusteringBound<?> end, |
| boolean hasPreviousBlock, |
| boolean hasNextBlock) throws IOException |
| { |
| // start != null means it's the block covering the beginning of the slice, so it has to be the last block for this slice. |
| assert start == null || !hasNextBlock; |
| |
| buffer.reset(); |
| skipFirstIteratedItem = false; |
| skipLastIteratedItem = false; |
| |
| // If the start might be in this block, skip everything that comes before it. |
| if (start != null) |
| { |
| while (deserializer.hasNext() && deserializer.compareNextTo(start) <= 0 && !stopReadingDisk()) |
| { |
| if (deserializer.nextIsRow()) |
| deserializer.skipNext(); |
| else |
| updateOpenMarker((RangeTombstoneMarker)deserializer.readNext()); |
| } |
| } |
| |
| // If we have an open marker, it's either one from what we just skipped or it's one that open in the next (or |
| // one of the next) index block (if openMarker == openMarkerAtStartOfBlock). |
| if (openMarker != null) |
| { |
| // We have to feed a marker to the buffer, because that marker is likely to be close later and ImmtableBTreePartition |
| // doesn't take kindly to marker that comes without their counterpart. If that's the last block we're gonna read (for |
| // the current slice at least) it's easy because we'll want to return that open marker at the end of the data in this |
| // block anyway, so we have nothing more to do than adding it to the buffer. |
| // If it's not the last block however, in which case we know we'll have start == null, it means this marker is really |
| // open in a next block and so while we do need to add it the buffer for the reason mentioned above, we don't |
| // want to "return" it just yet, we'll wait until we reach it in the next blocks. That's why we trigger |
| // skipLastIteratedItem in that case (this is first item of the block, but we're iterating in reverse order |
| // so it will be last returned by the iterator). |
| ClusteringBound<?> markerStart = start == null ? BufferClusteringBound.BOTTOM : start; |
| buffer.add(new RangeTombstoneBoundMarker(markerStart, openMarker)); |
| if (hasNextBlock) |
| skipLastIteratedItem = true; |
| } |
| |
| // Now deserialize everything until we reach our requested end (if we have one) |
| // See SSTableIterator.ForwardRead.computeNext() for why this is a strict inequality below: this is the same |
| // reasoning here. |
| while (deserializer.hasNext() |
| && (end == null || deserializer.compareNextTo(end) < 0) |
| && !stopReadingDisk()) |
| { |
| Unfiltered unfiltered = deserializer.readNext(); |
| UnfilteredValidation.maybeValidateUnfiltered(unfiltered, metadata(), key, sstable); |
| // We may get empty row for the same reason expressed on UnfilteredSerializer.deserializeOne. |
| if (!unfiltered.isEmpty()) |
| buffer.add(unfiltered); |
| |
| if (unfiltered.isRangeTombstoneMarker()) |
| updateOpenMarker((RangeTombstoneMarker)unfiltered); |
| } |
| |
| // If we have an open marker, we should close it before finishing |
| if (openMarker != null) |
| { |
| // This is the reverse problem than the one at the start of the block. Namely, if it's the first block |
| // we deserialize for the slice (the one covering the slice end basically), then it's easy, we just want |
| // to add the close marker to the buffer and return it normally. |
| // If it's note our first block (for the slice) however, it means that marker closed in a previously read |
| // block and we have already returned it. So while we should still add it to the buffer for the sake of |
| // not breaking ImmutableBTreePartition, we should skip it when returning from the iterator, hence the |
| // skipFirstIteratedItem (this is the last item of the block, but we're iterating in reverse order so it will |
| // be the first returned by the iterator). |
| ClusteringBound<?> markerEnd = end == null ? BufferClusteringBound.TOP : end; |
| buffer.add(new RangeTombstoneBoundMarker(markerEnd, openMarker)); |
| if (hasPreviousBlock) |
| skipFirstIteratedItem = true; |
| } |
| |
| buffer.build(); |
| } |
| } |
| |
| private class ReverseIndexedReader extends ReverseReader |
| { |
| private final IndexState indexState; |
| |
| // The slice we're currently iterating over |
| private Slice slice; |
| // The last index block to consider for the slice |
| private int lastBlockIdx; |
| |
| private ReverseIndexedReader(RowIndexEntry indexEntry, FileDataInput file, boolean shouldCloseFile) |
| { |
| super(file, shouldCloseFile); |
| this.indexState = new IndexState(this, metadata.comparator, indexEntry, true, ifile); |
| } |
| |
| @Override |
| public void close() throws IOException |
| { |
| super.close(); |
| this.indexState.close(); |
| } |
| |
| @Override |
| public void setForSlice(Slice slice) throws IOException |
| { |
| this.slice = slice; |
| |
| // if our previous slicing already got us past the beginning of the sstable, we're done |
| if (indexState.isDone()) |
| { |
| iterator = Collections.emptyIterator(); |
| return; |
| } |
| |
| // Find the first index block we'll need to read for the slice. |
| int startIdx = indexState.findBlockIndex(slice.end(), indexState.currentBlockIdx()); |
| if (startIdx < 0) |
| { |
| iterator = Collections.emptyIterator(); |
| indexState.setToBlock(startIdx); |
| return; |
| } |
| |
| lastBlockIdx = indexState.findBlockIndex(slice.start(), startIdx); |
| |
| // If the last block to look (in reverse order) is after the very last block, we have nothing for that slice |
| if (lastBlockIdx >= indexState.blocksCount()) |
| { |
| assert startIdx >= indexState.blocksCount(); |
| iterator = Collections.emptyIterator(); |
| return; |
| } |
| |
| // If we start (in reverse order) after the very last block, just read from the last one. |
| if (startIdx >= indexState.blocksCount()) |
| startIdx = indexState.blocksCount() - 1; |
| |
| // Note that even if we were already set on the proper block (which would happen if the previous slice |
| // requested ended on the same block this one start), we can't reuse it because when reading the previous |
| // slice we've only read that block from the previous slice start. Re-reading also handles |
| // skipFirstIteratedItem/skipLastIteratedItem that we would need to handle otherwise. |
| indexState.setToBlock(startIdx); |
| |
| readCurrentBlock(false, startIdx != lastBlockIdx); |
| } |
| |
| @Override |
| protected boolean hasNextInternal() throws IOException |
| { |
| if (super.hasNextInternal()) |
| return true; |
| |
| while (true) |
| { |
| // We have nothing more for our current block, move the next one (so the one before on disk). |
| int nextBlockIdx = indexState.currentBlockIdx() - 1; |
| if (nextBlockIdx < 0 || nextBlockIdx < lastBlockIdx) |
| return false; |
| |
| // The slice start can be in |
| indexState.setToBlock(nextBlockIdx); |
| readCurrentBlock(true, nextBlockIdx != lastBlockIdx); |
| |
| // If an indexed block only contains data for a dropped column, the iterator will be empty, even |
| // though we may still have data to read in subsequent blocks |
| |
| // also, for pre-3.0 storage formats, index blocks that only contain a single row and that row crosses |
| // index boundaries, the iterator will be empty even though we haven't read everything we're intending |
| // to read. In that case, we want to read the next index block. This shouldn't be possible in 3.0+ |
| // formats (see next comment) |
| if (!iterator.hasNext() && nextBlockIdx > lastBlockIdx) |
| { |
| continue; |
| } |
| |
| return iterator.hasNext(); |
| } |
| } |
| |
| /** |
| * Reads the current block, the last one we've set. |
| * |
| * @param hasPreviousBlock is whether we have already read a previous block for the current slice. |
| * @param hasNextBlock is whether we have more blocks to read for the current slice. |
| */ |
| private void readCurrentBlock(boolean hasPreviousBlock, boolean hasNextBlock) throws IOException |
| { |
| if (buffer == null) |
| buffer = createBuffer(indexState.blocksCount()); |
| |
| // The slice start (resp. slice end) is only meaningful on the last (resp. first) block read (since again, |
| // we read blocks in reverse order). |
| boolean canIncludeSliceStart = !hasNextBlock; |
| boolean canIncludeSliceEnd = !hasPreviousBlock; |
| |
| loadFromDisk(canIncludeSliceStart ? slice.start() : null, |
| canIncludeSliceEnd ? slice.end() : null, |
| hasPreviousBlock, |
| hasNextBlock); |
| setIterator(slice); |
| } |
| |
| @Override |
| protected boolean stopReadingDisk() throws IOException |
| { |
| return indexState.isPastCurrentBlock(); |
| } |
| } |
| |
| private class ReusablePartitionData |
| { |
| private final TableMetadata metadata; |
| private final DecoratedKey partitionKey; |
| private final RegularAndStaticColumns columns; |
| |
| private MutableDeletionInfo.Builder deletionBuilder; |
| private MutableDeletionInfo deletionInfo; |
| private BTree.Builder<Row> rowBuilder; |
| private ImmutableBTreePartition built; |
| |
| private ReusablePartitionData(TableMetadata metadata, |
| DecoratedKey partitionKey, |
| RegularAndStaticColumns columns, |
| int initialRowCapacity) |
| { |
| this.metadata = metadata; |
| this.partitionKey = partitionKey; |
| this.columns = columns; |
| this.rowBuilder = BTree.builder(metadata.comparator, initialRowCapacity); |
| } |
| |
| |
| public void add(Unfiltered unfiltered) |
| { |
| if (unfiltered.isRow()) |
| rowBuilder.add((Row)unfiltered); |
| else |
| deletionBuilder.add((RangeTombstoneMarker)unfiltered); |
| } |
| |
| public void reset() |
| { |
| built = null; |
| rowBuilder.reuse(); |
| deletionBuilder = MutableDeletionInfo.builder(partitionLevelDeletion, metadata().comparator, false); |
| } |
| |
| public void build() |
| { |
| deletionInfo = deletionBuilder.build(); |
| built = new ImmutableBTreePartition(metadata, partitionKey, columns, Rows.EMPTY_STATIC_ROW, rowBuilder.build(), |
| deletionInfo, EncodingStats.NO_STATS); |
| deletionBuilder = null; |
| } |
| } |
| |
| private static class SkipLastIterator extends AbstractIterator<Unfiltered> |
| { |
| private final Iterator<Unfiltered> iterator; |
| |
| private SkipLastIterator(Iterator<Unfiltered> iterator) |
| { |
| this.iterator = iterator; |
| } |
| |
| protected Unfiltered computeNext() |
| { |
| if (!iterator.hasNext()) |
| return endOfData(); |
| |
| Unfiltered next = iterator.next(); |
| return iterator.hasNext() ? next : endOfData(); |
| } |
| } |
| } |