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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.

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/*
 * 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.Collection;
import java.util.List;
import java.util.Set;

import com.google.common.collect.Lists;

import org.apache.cassandra.cql3.statements.schema.IndexTarget;
import org.apache.cassandra.db.ColumnFamilyStore;
import org.apache.cassandra.db.DataRange;
import org.apache.cassandra.db.DecoratedKey;
import org.apache.cassandra.db.PartitionPosition;
import org.apache.cassandra.db.PartitionRangeReadCommand;
import org.apache.cassandra.db.ReadCommand;
import org.apache.cassandra.db.ReadExecutionController;
import org.apache.cassandra.db.SinglePartitionReadCommand;
import org.apache.cassandra.db.filter.ClusteringIndexFilter;
import org.apache.cassandra.db.filter.ClusteringIndexNamesFilter;
import org.apache.cassandra.db.filter.DataLimits;
import org.apache.cassandra.db.filter.RowFilter;
import org.apache.cassandra.db.rows.UnfilteredRowIterator;
import org.apache.cassandra.dht.AbstractBounds;
import org.apache.cassandra.dht.Range;
import org.apache.cassandra.index.sai.IndexContext;
import org.apache.cassandra.index.sai.QueryContext;
import org.apache.cassandra.index.sai.StorageAttachedIndex;
import org.apache.cassandra.index.sai.disk.IndexSearchResultIterator;
import org.apache.cassandra.index.sai.disk.SSTableIndex;
import org.apache.cassandra.index.sai.iterators.KeyRangeIntersectionIterator;
import org.apache.cassandra.index.sai.iterators.KeyRangeIterator;
import org.apache.cassandra.index.sai.metrics.TableQueryMetrics;
import org.apache.cassandra.index.sai.utils.PrimaryKey;
import org.apache.cassandra.schema.TableMetadata;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.Pair;

public class QueryController
{
    private final ColumnFamilyStore cfs;
    private final ReadCommand command;
    private final QueryContext queryContext;
    private final TableQueryMetrics tableQueryMetrics;
    private final RowFilter filterOperation;
    private final List ranges;
    private final AbstractBounds mergeRange;

    public QueryController(ColumnFamilyStore cfs,
                           ReadCommand command,
                           RowFilter filterOperation,
                           QueryContext queryContext,
                           TableQueryMetrics tableQueryMetrics)
    {
        this.cfs = cfs;
        this.command = command;
        this.queryContext = queryContext;
        this.tableQueryMetrics = tableQueryMetrics;
        this.filterOperation = filterOperation;
        this.ranges = dataRanges(command);
        DataRange first = ranges.get(0);
        DataRange last = ranges.get(ranges.size() - 1);
        this.mergeRange = ranges.size() == 1 ? first.keyRange() : first.keyRange().withNewRight(last.keyRange().right);
    }

    public TableMetadata metadata()
    {
        return command.metadata();
    }

    RowFilter filterOperation()
    {
        return this.filterOperation;
    }

    /**
     * @return token ranges used in the read command
     */
    List dataRanges()
    {
        return ranges;
    }

    /**
     * Note: merged range may contain subrange that no longer belongs to the local node after range movement.
     * It should only be used as an optimization to reduce search space. Use {@link #dataRanges()} instead to filter data.
     *
     * @return merged token range
     */
    AbstractBounds mergeRange()
    {
        return mergeRange;
    }

    /**
     * @return indexed {@code IndexContext} if index is found; otherwise return non-indexed {@code IndexContext}.
     */
    public IndexContext getContext(RowFilter.Expression expression)
    {
        Set indexes = cfs.indexManager.getBestIndexFor(expression, StorageAttachedIndex.class);

        return indexes.isEmpty() ? new IndexContext(cfs.metadata().keyspace,
                                                    cfs.metadata().name,
                                                    cfs.metadata().partitionKeyType,
                                                    cfs.metadata().comparator,
                                                    expression.column(),
                                                    IndexTarget.Type.VALUES,
                                                    null)
                                 : indexes.iterator().next().getIndexContext();
    }

    public UnfilteredRowIterator queryStorage(PrimaryKey key, ReadExecutionController executionController)
    {
        if (key == null)
            throw new IllegalArgumentException("non-null key required");

        try
        {
            SinglePartitionReadCommand partition = SinglePartitionReadCommand.create(cfs.metadata(),
                                                                                     command.nowInSec(),
                                                                                     command.columnFilter(),
                                                                                     RowFilter.none(),
                                                                                     DataLimits.NONE,
                                                                                     key.partitionKey(),
                                                                                     makeFilter(key));

            return partition.queryMemtableAndDisk(cfs, executionController);
        }
        finally
        {
            queryContext.checkpoint();
        }
    }

    /**
     * Build a {@link KeyRangeIterator.Builder} from the given list of {@link Expression}s.
     * 

* This is achieved by creating an on-disk view of the query that maps the expressions to * the {@link SSTableIndex}s that will satisfy the expression. *

* Each (expression, SSTable indexes) pair is then passed to * {@link IndexSearchResultIterator#build(Expression, Collection, AbstractBounds, QueryContext)} * to search the in-memory index associated with the expression and the SSTable indexes, the results of * which are unioned and returned. *

* The results from each call to {@link IndexSearchResultIterator#build(Expression, Collection, AbstractBounds, QueryContext)} * are added to a {@link KeyRangeIntersectionIterator} and returned. */ public KeyRangeIterator.Builder getIndexQueryResults(Collection expressions) { KeyRangeIterator.Builder builder = KeyRangeIntersectionIterator.builder(expressions.size()); QueryViewBuilder queryViewBuilder = new QueryViewBuilder(expressions, mergeRange); Collection>> queryView = queryViewBuilder.build(); try { for (Pair> queryViewPair : queryView) { @SuppressWarnings({"resource", "RedundantSuppression"}) // RangeIterators are closed by releaseIndexes KeyRangeIterator index = IndexSearchResultIterator.build(queryViewPair.left, queryViewPair.right, mergeRange, queryContext); builder.add(index); } } catch (Throwable t) { // all sstable indexes in view have been referenced, need to clean up when exception is thrown builder.cleanup(); queryView.forEach(pair -> pair.right.forEach(SSTableIndex::releaseQuietly)); throw t; } return builder; } /** * Returns whether this query is not selecting the {@link PrimaryKey}. * The query does not select the key if both of the following statements are false: * 1. The table associated with the query is not using clustering keys * 2. The clustering index filter for the command wants the row. * * Item 2 is important in paged queries where the {@link org.apache.cassandra.db.filter.ClusteringIndexSliceFilter} for * subsequent paged queries may not select rows that are returned by the index * search because that is initially partition based. * * @param key The {@link PrimaryKey} to be tested * @return true if the key is not selected by the query */ public boolean doesNotSelect(PrimaryKey key) { return !key.hasEmptyClustering() && !command.clusteringIndexFilter(key.partitionKey()).selects(key.clustering()); } // Note: This method assumes that the selects method has already been called for the // key to avoid having to (potentially) call selects twice private ClusteringIndexFilter makeFilter(PrimaryKey key) { ClusteringIndexFilter clusteringIndexFilter = command.clusteringIndexFilter(key.partitionKey()); if (key.hasEmptyClustering()) return clusteringIndexFilter; else return new ClusteringIndexNamesFilter(FBUtilities.singleton(key.clustering(), cfs.metadata().comparator), clusteringIndexFilter.isReversed()); } /** * Used to release all resources and record metrics when query finishes. */ public void finish() { if (tableQueryMetrics != null) tableQueryMetrics.record(queryContext); } /** * Returns the {@link DataRange} list covered by the specified {@link ReadCommand}. * * @param command a read command * @return the data ranges covered by {@code command} */ private static List dataRanges(ReadCommand command) { if (command instanceof SinglePartitionReadCommand) { SinglePartitionReadCommand cmd = (SinglePartitionReadCommand) command; DecoratedKey key = cmd.partitionKey(); return Lists.newArrayList(new DataRange(new Range<>(key, key), cmd.clusteringIndexFilter())); } else if (command instanceof PartitionRangeReadCommand) { PartitionRangeReadCommand cmd = (PartitionRangeReadCommand) command; return Lists.newArrayList(cmd.dataRange()); } else { throw new AssertionError("Unsupported read command type: " + command.getClass().getName()); } } }





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