Source Code Cross Referenced for GroupedResult.java in  » Database-DBMS » hsql » org » hsqldb » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Database DBMS » hsql » org.hsqldb 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /* Copyright (c) 2001-2005, The HSQL Development Group
002:         * All rights reserved.
003:         *
004:         * Redistribution and use in source and binary forms, with or without
005:         * modification, are permitted provided that the following conditions are met:
006:         *
007:         * Redistributions of source code must retain the above copyright notice, this
008:         * list of conditions and the following disclaimer.
009:         *
010:         * Redistributions in binary form must reproduce the above copyright notice,
011:         * this list of conditions and the following disclaimer in the documentation
012:         * and/or other materials provided with the distribution.
013:         *
014:         * Neither the name of the HSQL Development Group nor the names of its
015:         * contributors may be used to endorse or promote products derived from this
016:         * software without specific prior written permission.
017:         *
018:         * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
019:         * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
020:         * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
021:         * ARE DISCLAIMED. IN NO EVENT SHALL HSQL DEVELOPMENT GROUP, HSQLDB.ORG,
022:         * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
023:         * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
024:         * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
025:         * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
026:         * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
027:         * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
028:         * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
029:         */
030:
031:        package org.hsqldb;
032:
033:        import org.hsqldb.lib.ArrayUtil;
034:        import org.hsqldb.lib.HashSet;
035:        import org.hsqldb.lib.Iterator;
036:
037:        /**
038:         * This class is used for grouping select results, especially for select
039:         * statements that include group by clause and nested aggregate functions.
040:         * It is used by the <b>Select</b> class regardless the existence of group by
041:         * clause.
042:         * <p>
043:         * When a group by clause is defined, a <b>ResultGroup</b> is used to hold
044:         * all column values and <b>AggregatingValue</b>s for each group.  When a group
045:         * by clause is not defined, one <b>ResultGroup</b> is used to hold all the
046:         * results.<p>
047:         *
048:         * All <b>ResultGroup</b>s are placed in a <b>HashSet</b>.  Adding a new row
049:         * will first retrieve the corresponding group from the table, based on the
050:         * values in the group by columns.  If a group is found, then the row
051:         * associated with the group will be returned.  Otherwise a new group is
052:         * created with the new row, and the new row is returned.
053:         * <p>
054:         * The <b>Select</b> can then update the values and <b>AggregatingValue</b>s
055:         * in the returned row, rather than the original row.  This approach enables
056:         * nested aggregate functions, such as "count(id)+2, 20-count(id),
057:         * max(id)-min(id)" support.
058:         *
059:         * @author  Tony Lai
060:         * @version   1.7.2
061:         * @since   1.7.2
062:         * @see     Expression
063:         * @see     Select
064:         */
065:
066:        // fredt@users - patch 1.7.2 - mods to use new HashSet class and to separate addRow and getRow operations
067:        class GroupedResult {
068:
069:            /** @todo fredt - initialise results on first use */
070:            private Result result;
071:            int groupBegin;
072:            int groupEnd;
073:            private final boolean isGrouped;
074:            private final boolean isAggregated;
075:            private HashSet groups;
076:            private ResultGroup currGroup;
077:
078:            GroupedResult(Select select, Result.ResultMetaData meta) {
079:
080:                result = new Result(meta);
081:                groupBegin = select.iResultLen;
082:                groupEnd = groupBegin + select.iGroupLen;
083:                isGrouped = groupBegin != groupEnd;
084:                isAggregated = select.isAggregated;
085:
086:                if (isGrouped) {
087:                    groups = new HashSet();
088:                }
089:            }
090:
091:            Object[] getRow(Object[] row) {
092:
093:                if (isGrouped) {
094:                    ResultGroup newGroup = new ResultGroup(row);
095:                    ResultGroup group = (ResultGroup) groups.get(newGroup);
096:
097:                    if (group != null) {
098:                        ArrayUtil.copyArray(group.row, row, row.length);
099:                    }
100:                } else if (isAggregated) {
101:                    if (currGroup != null) {
102:                        ArrayUtil.copyArray(currGroup.row, row, row.length);
103:                    }
104:                }
105:
106:                return row;
107:            }
108:
109:            void addRow(Object[] row) {
110:
111:                if (isGrouped) {
112:                    ResultGroup newGroup = new ResultGroup(row);
113:
114:                    currGroup = (ResultGroup) groups.get(newGroup);
115:
116:                    if (currGroup == null) {
117:                        currGroup = newGroup;
118:
119:                        groups.add(currGroup);
120:                        result.add(row);
121:                    } else {
122:                        System.arraycopy(row, 0, currGroup.row, 0, row.length);
123:                    }
124:                } else if (isAggregated) {
125:                    if (currGroup == null) {
126:                        currGroup = new ResultGroup(row);
127:
128:                        result.add(row);
129:                    } else {
130:                        System.arraycopy(row, 0, currGroup.row, 0, row.length);
131:                    }
132:                } else {
133:                    result.add(row);
134:                }
135:            }
136:
137:            int size() {
138:                return result.getSize();
139:            }
140:
141:            Iterator iterator() {
142:                return result.iterator();
143:            }
144:
145:            Result getResult() {
146:                return result;
147:            }
148:
149:            class ResultGroup {
150:
151:                Object[] row;
152:                int hashCode;
153:
154:                private ResultGroup(Object[] row) {
155:
156:                    this .row = row;
157:                    hashCode = 0;
158:
159:                    for (int i = groupBegin; i < groupEnd; i++) {
160:                        if (row[i] != null) {
161:                            hashCode += row[i].hashCode();
162:                        }
163:                    }
164:                }
165:
166:                public int hashCode() {
167:                    return hashCode;
168:                }
169:
170:                public boolean equals(Object obj) {
171:
172:                    if (obj == this ) {
173:                        return true;
174:                    }
175:
176:                    if (obj == null || !(obj instanceof  ResultGroup)) {
177:                        return false;
178:                    }
179:
180:                    ResultGroup group = (ResultGroup) obj;
181:
182:                    for (int i = groupBegin; i < groupEnd; i++) {
183:                        if (!equals(row[i], group.row[i])) {
184:                            return false;
185:                        }
186:                    }
187:
188:                    return true;
189:                }
190:
191:                private boolean equals(Object o1, Object o2) {
192:                    return (o1 == null) ? o2 == null : o1.equals(o2);
193:                }
194:            }
195:        }
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