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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.db;

import org.apache.cassandra.cql3.ColumnIdentifier;
import org.apache.cassandra.db.filter.ColumnFilter;
import org.apache.cassandra.db.filter.DataLimits;
import org.apache.cassandra.db.filter.RowFilter;
import org.apache.cassandra.db.monitoring.MonitorableImpl;
import org.apache.cassandra.db.partitions.PartitionIterator;
import org.apache.cassandra.db.partitions.UnfilteredPartitionIterators;
import org.apache.cassandra.schema.TableMetadata;

/**
 * Base class for {@code ReadQuery} implementations.
 */
abstract class AbstractReadQuery extends MonitorableImpl implements ReadQuery
{
    private final TableMetadata metadata;
    private final long nowInSec;

    private final ColumnFilter columnFilter;
    private final RowFilter rowFilter;
    private final DataLimits limits;

    protected AbstractReadQuery(TableMetadata metadata, long nowInSec, ColumnFilter columnFilter, RowFilter rowFilter, DataLimits limits)
    {
        this.metadata = metadata;
        this.nowInSec = nowInSec;
        this.columnFilter = columnFilter;
        this.rowFilter = rowFilter;
        this.limits = limits;
    }

    @Override
    public TableMetadata metadata()
    {
        return metadata;
    }

    // Monitorable interface
    public String name()
    {
        return toCQLString();
    }

    @Override
    public PartitionIterator executeInternal(ReadExecutionController controller)
    {
        return UnfilteredPartitionIterators.filter(executeLocally(controller), nowInSec());
    }

    @Override
    public DataLimits limits()
    {
        return limits;
    }

    @Override
    public long nowInSec()
    {
        return nowInSec;
    }

    @Override
    public RowFilter rowFilter()
    {
        return rowFilter;
    }

    @Override
    public ColumnFilter columnFilter()
    {
        return columnFilter;
    }

    /**
     * Recreate the CQL string corresponding to this query.
     * 
     * Note that in general the returned string will not be exactly the original user string, first
     * because there isn't always a single syntax for a given query,  but also because we don't have
     * all the information needed (we know the non-PK columns queried but not the PK ones as internally
     * we query them all). So this shouldn't be relied too strongly, but this should be good enough for
     * debugging purpose which is what this is for.
     */
    public String toCQLString()
    {
        StringBuilder sb = new StringBuilder().append("SELECT ")
                                              .append(columnFilter().toCQLString())
                                              .append(" FROM ")
                                              .append(ColumnIdentifier.maybeQuote(metadata().keyspace))
                                              .append('.')
                                              .append(ColumnIdentifier.maybeQuote(metadata().name));
        appendCQLWhereClause(sb);

        if (limits() != DataLimits.NONE)
            sb.append(' ').append(limits());

        // ALLOW FILTERING might not be strictly necessary
        sb.append(" ALLOW FILTERING");

        return sb.toString();
    }

    protected abstract void appendCQLWhereClause(StringBuilder sb);
}