distinctscanresultset.java

derby database source code.good for you.

/*

   Derby - Class org.apache.derby.impl.sql.execute.DistinctScanResultSet

   Copyright 1999, 2004 The Apache Software Foundation or its licensors, as applicable.

   Licensed 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.derby.impl.sql.execute;

import org.apache.derby.iapi.services.loader.GeneratedMethod;

import org.apache.derby.iapi.services.monitor.Monitor;

import org.apache.derby.iapi.services.sanity.SanityManager;

import org.apache.derby.iapi.services.io.Storable;

import org.apache.derby.iapi.services.stream.HeaderPrintWriter;
import org.apache.derby.iapi.services.stream.InfoStreams;

import org.apache.derby.iapi.sql.conn.LanguageConnectionContext;

import org.apache.derby.iapi.error.StandardException;


import org.apache.derby.iapi.sql.execute.CursorResultSet;
import org.apache.derby.iapi.sql.execute.ExecIndexRow;
import org.apache.derby.iapi.sql.execute.ExecRow;
import org.apache.derby.iapi.sql.execute.ExecutionContext;
import org.apache.derby.iapi.sql.execute.NoPutResultSet;

import org.apache.derby.iapi.sql.Activation;
import org.apache.derby.iapi.sql.ResultSet;

import org.apache.derby.iapi.store.access.ConglomerateController;
import org.apache.derby.iapi.store.access.Qualifier;
import org.apache.derby.iapi.store.access.ScanController;
import org.apache.derby.iapi.store.access.StaticCompiledOpenConglomInfo;
import org.apache.derby.iapi.store.access.TransactionController;

import org.apache.derby.iapi.types.RowLocation;

import org.apache.derby.iapi.services.io.FormatableBitSet;
import org.apache.derby.iapi.services.io.FormatableArrayHolder;
import org.apache.derby.iapi.services.io.FormatableIntHolder;

import java.util.Enumeration;
import java.util.Properties;
import java.util.Vector;

/**
 * Eliminates duplicates while scanning the underlying conglomerate.
 * (Assumes no predicates, for now.)
 *
 * @author jerry
 */
public class DistinctScanResultSet extends HashScanResultSet
{

	Enumeration element = null;


    //
    // class interface
    //
    public DistinctScanResultSet(long conglomId, 
		StaticCompiledOpenConglomInfo scoci, Activation activation, 
		GeneratedMethod resultRowAllocator, 
		int resultSetNumber,
		int hashKeyItem,
		String tableName,
		String indexName,
		boolean isConstraint,
		int colRefItem,
		int lockMode,
		boolean tableLocked,
		int isolationLevel,
		double optimizerEstimatedRowCount,
		double optimizerEstimatedCost,
		GeneratedMethod closeCleanup)
			throws StandardException
    {
		super(conglomId, scoci, activation, resultRowAllocator, resultSetNumber,
			  (GeneratedMethod) null, // startKeyGetter
			  0,					  // startSearchOperator
			  (GeneratedMethod) null, // stopKeyGetter
			  0,					  // stopSearchOperator
			  false,				  // sameStartStopPosition
			  (Qualifier[][]) null,	  // scanQualifiers
			  (Qualifier[][]) null,	  // nextQualifiers
			  DEFAULT_INITIAL_CAPACITY, DEFAULT_LOADFACTOR, DEFAULT_MAX_CAPACITY,
			  hashKeyItem, tableName, indexName, isConstraint, 
			  false,				  // forUpdate
			  colRefItem, lockMode, tableLocked, isolationLevel,
			  false,
			  optimizerEstimatedRowCount, optimizerEstimatedCost, closeCleanup);

		// Tell super class to eliminate duplicates
		eliminateDuplicates = true;
    }

	//
	// ResultSet interface (override methods from HashScanResultSet)
	//

	/**
     * Return the next row (if any) from the scan (if open).
	 *
	 * @exception StandardException thrown on failure to get next row
	 */
	public ExecRow getNextRowCore() throws StandardException
	{
	    ExecRow result = null;
		Object[] columns = null;

		beginTime = getCurrentTimeMillis();
	    if ( isOpen )
	    {
			if (firstNext)
			{
				element = hashtable.elements();
				firstNext = false;
			}

			if (element.hasMoreElements())
			{
				columns = (Object[]) element.nextElement();

				setCompatRow(compactRow, columns);

				rowsSeen++;

				result = compactRow;
			}
			// else done
		}

		currentRow = result;
		setCurrentRow(result);

		nextTime += getElapsedMillis(beginTime);
	    return result;
	}
}