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HSQLDB example source code file (GroupedResult.java)
The HSQLDB GroupedResult.java source code/* Copyright (c) 2001-2008, The HSQL Development Group * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * Redistributions of source code must retain the above copyright notice, this * list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * Neither the name of the HSQL Development Group nor the names of its * contributors may be used to endorse or promote products derived from this * software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG, * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ package org.hsqldb; import org.hsqldb.lib.ArrayUtil; import org.hsqldb.lib.HashSet; import org.hsqldb.lib.Iterator; /** * This class is used for grouping select results, especially for select * statements that include group by clause and nested aggregate functions. * It is used by the <b>Select class regardless the existence of group by * clause. * <p> * When a group by clause is defined, a <b>ResultGroup is used to hold * all column values and <b>AggregatingValues for each group. When a group * by clause is not defined, one <b>ResultGroup is used to hold all the * results.<p> * * All <b>ResultGroups are placed in a HashSet. Adding a new row * will first retrieve the corresponding group from the table, based on the * values in the group by columns. If a group is found, then the row * associated with the group will be returned. Otherwise a new group is * created with the new row, and the new row is returned. * <p> * The <b>Select can then update the values and AggregatingValues * in the returned row, rather than the original row. This approach enables * nested aggregate functions, such as "count(id)+2, 20-count(id), * max(id)-min(id)" support. * * @author Tony Lai * @version 1.7.2 * @since 1.7.2 * @see Expression * @see Select */ // fredt@users - patch 1.7.2 - mods to use new HashSet class and to separate addRow and getRow operations class GroupedResult { /** @todo fredt - initialise results on first use */ private Result result; int groupBegin; int groupEnd; private final boolean isGrouped; private final boolean isAggregated; private HashSet groups; private ResultGroup currGroup; GroupedResult(Select select, Result.ResultMetaData meta) { result = new Result(meta); groupBegin = select.iResultLen; groupEnd = groupBegin + select.iGroupLen; isGrouped = groupBegin != groupEnd; isAggregated = select.isAggregated; if (isGrouped) { groups = new HashSet(); } } Object[] getRow(Object[] row) { if (isGrouped) { ResultGroup newGroup = new ResultGroup(row); ResultGroup group = (ResultGroup) groups.get(newGroup); if (group != null) { ArrayUtil.copyArray(group.row, row, row.length); } } else if (isAggregated) { if (currGroup != null) { ArrayUtil.copyArray(currGroup.row, row, row.length); } } return row; } void addRow(Object[] row) { if (isGrouped) { ResultGroup newGroup = new ResultGroup(row); currGroup = (ResultGroup) groups.get(newGroup); if (currGroup == null) { currGroup = newGroup; groups.add(currGroup); result.add(row); } else { System.arraycopy(row, 0, currGroup.row, 0, row.length); } } else if (isAggregated) { if (currGroup == null) { currGroup = new ResultGroup(row); result.add(row); } else { System.arraycopy(row, 0, currGroup.row, 0, row.length); } } else { result.add(row); } } int size() { return result.getSize(); } Iterator iterator() { return result.iterator(); } Result getResult() { return result; } class ResultGroup { Object[] row; int hashCode; private ResultGroup(Object[] row) { this.row = row; hashCode = 0; for (int i = groupBegin; i < groupEnd; i++) { if (row[i] != null) { hashCode += row[i].hashCode(); } } } public int hashCode() { return hashCode; } public boolean equals(Object obj) { if (obj == this) { return true; } if (obj == null ||!(obj instanceof ResultGroup)) { return false; } ResultGroup group = (ResultGroup) obj; for (int i = groupBegin; i < groupEnd; i++) { if (!equals(row[i], group.row[i])) { return false; } } return true; } private boolean equals(Object o1, Object o2) { return (o1 == null) ? o2 == null : o1.equals(o2); } } } Other HSQLDB examples (source code examples)Here is a short list of links related to this HSQLDB GroupedResult.java source code file: |
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