Source Code Cross Referenced for MergeCursor.java in  » Database-DBMS » Quadcap-Embeddable-Database » com » quadcap » sql » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Database DBMS » Quadcap Embeddable Database » com.quadcap.sql 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        package com.quadcap.sql;
002:
003:        /* Copyright 1999 - 2003 Quadcap Software.  All rights reserved.
004:         *
005:         * This software is distributed under the Quadcap Free Software License.
006:         * This software may be used or modified for any purpose, personal or
007:         * commercial.  Open Source redistributions are permitted.  Commercial
008:         * redistribution of larger works derived from, or works which bundle
009:         * this software requires a "Commercial Redistribution License"; see
010:         * http://www.quadcap.com/purchase.
011:         *
012:         * Redistributions qualify as "Open Source" under  one of the following terms:
013:         *   
014:         *    Redistributions are made at no charge beyond the reasonable cost of
015:         *    materials and delivery.
016:         *
017:         *    Redistributions are accompanied by a copy of the Source Code or by an
018:         *    irrevocable offer to provide a copy of the Source Code for up to three
019:         *    years at the cost of materials and delivery.  Such redistributions
020:         *    must allow further use, modification, and redistribution of the Source
021:         *    Code under substantially the same terms as this license.
022:         *
023:         * Redistributions of source code must retain the copyright notices as they
024:         * appear in each source code file, these license terms, and the
025:         * disclaimer/limitation of liability set forth as paragraph 6 below.
026:         *
027:         * Redistributions in binary form must reproduce this Copyright Notice,
028:         * these license terms, and the disclaimer/limitation of liability set
029:         * forth as paragraph 6 below, in the documentation and/or other materials
030:         * provided with the distribution.
031:         *
032:         * The Software is provided on an "AS IS" basis.  No warranty is
033:         * provided that the Software is free of defects, or fit for a
034:         * particular purpose.  
035:         *
036:         * Limitation of Liability. Quadcap Software shall not be liable
037:         * for any damages suffered by the Licensee or any third party resulting
038:         * from use of the Software.
039:         */
040:
041:        import java.io.ByteArrayInputStream;
042:        import java.io.Externalizable;
043:        import java.io.IOException;
044:        import java.io.ObjectInput;
045:        import java.io.ObjectOutput;
046:
047:        import java.util.Vector;
048:
049:        import java.sql.SQLException;
050:
051:        import com.quadcap.sql.io.ObjectInputStream;
052:        import com.quadcap.sql.io.ObjectOutputStream;
053:
054:        import com.quadcap.sql.file.ByteUtil;
055:
056:        import com.quadcap.sql.index.BCursor;
057:        import com.quadcap.sql.index.Btree;
058:
059:        import com.quadcap.sql.types.Op;
060:        import com.quadcap.sql.types.Value;
061:
062:        import com.quadcap.util.Debug;
063:        import com.quadcap.util.Util;
064:
065:        /**
066:         * Cursor implementing the SQL <b>UNION</b> or <b>INTERSECTION</b> operations.
067:         * This cursor shares some functionality with the GroupByCursor class,
068:         * and factorization should be investigated.
069:         *
070:         * @author Stan Bailes
071:         */
072:        public class MergeCursor extends CursorImpl {
073:            int op;
074:            boolean all;
075:            TempTableMerge tempTable;
076:            LazyRow row = null;
077:            BCursor bc = null;
078:            int duplicateCount = 0;
079:
080:            public MergeCursor(Session session, int op, boolean all,
081:                    TempTableMerge tempTable) throws SQLException {
082:                super (session, null, null);
083:                this .op = op;
084:                this .all = all;
085:                this .tempTable = tempTable;
086:            }
087:
088:            public Row getRow() throws SQLException {
089:                return row;
090:            }
091:
092:            public void checkCursor() throws IOException {
093:                if (bc == null) {
094:                    bc = tempTable.getCursor();
095:                }
096:            }
097:
098:            public long getRowId() {
099:                byte[] val = bc.getValBuf();
100:                return val[0] == 1 ? 0 : ByteUtil.getLong(val, 1);
101:            }
102:
103:            public void resolveColumns() throws SQLException {
104:                super .resolveColumns();
105:                row = new LazyRow(getColumnCount());
106:                beforeFirst();
107:            }
108:
109:            public String getName() {
110:                return "";
111:            }
112:
113:            public long size() throws SQLException {
114:                try {
115:                    checkCursor();
116:                    return bc.size();
117:                } catch (IOException e) {
118:                    throw DbException.wrapThrowable(e);
119:                }
120:            }
121:
122:            public void afterLast() throws SQLException {
123:                throw new SQLException(
124:                        "afterLast() not supported for this cursor type");
125:            }
126:
127:            public boolean isWritable(int col) {
128:                return false;
129:            }
130:
131:            public boolean next() throws SQLException {
132:                try {
133:                    checkCursor();
134:                    switch (op) {
135:                    case Op.UNION:
136:                        return all ? nextUnionAll() : nextUnion();
137:                    case Op.INTERSECT:
138:                        return nextIntersect();
139:                    case Op.EXCEPT:
140:                        return nextExcept();
141:                    default:
142:                        throw new SQLException("Bad merge op: " + op, "42000");
143:                    }
144:                } catch (IOException e) {
145:                    throw DbException.wrapThrowable(e);
146:                }
147:            }
148:
149:            public void updateRow(Row row) throws SQLException {
150:                throw new SQLException("GroupBy expressions aren't updateable",
151:                        "42000");
152:            }
153:
154:            public void deleteRow() throws SQLException {
155:                throw new SQLException("GroupBy expressions aren't updateable",
156:                        "42000");
157:            }
158:
159:            public void beforeFirst() throws SQLException {
160:                try {
161:                    checkCursor();
162:                    bc.beforeFirst();
163:                } catch (IOException e) {
164:                    throw DbException.wrapThrowable(e);
165:                } finally {
166:                    duplicateCount = 0;
167:                }
168:            }
169:
170:            /**
171:             * Separate from 'nextUnionAll' because we can avoid fetching the
172:             * data for this case.
173:             */
174:            boolean nextUnion() throws SQLException, IOException {
175:                if (!bc.next())
176:                    return false;
177:                tempTable.getRow(bc.getValBuf(), row);
178:                return true;
179:            }
180:
181:            /**
182:             * Fetch the data once when we fetch the counts, then return each
183:             * row the required number of times
184:             */
185:            boolean nextUnionAll() throws SQLException, IOException {
186:                if (duplicateCount-- <= 0) {
187:                    if (!bc.next())
188:                        return false;
189:                    tempTable.getRow(bc.getValBuf(), row);
190:                    byte[] data = bc.getValBuf();
191:                    int acnt = TempTableMerge.getCount(data, 0);
192:                    int bcnt = TempTableMerge.getCount(data, 1);
193:                    duplicateCount = acnt + bcnt - 1;
194:                    return true;
195:                }
196:                return true;
197:            }
198:
199:            boolean nextIntersect() throws SQLException, IOException {
200:                if (!all || duplicateCount-- <= 0) {
201:                    boolean found = false;
202:                    do {
203:                        if (!bc.next())
204:                            return false;
205:                        byte[] data = bc.getValBuf();
206:                        int acnt = TempTableMerge.getCount(data, 0);
207:                        int bcnt = TempTableMerge.getCount(data, 1);
208:                        duplicateCount = all ? Math.min(acnt, bcnt)
209:                                : (acnt > 0 && bcnt > 0) ? 1 : 0;
210:                        if (duplicateCount-- > 0) {
211:                            tempTable.getRow(data, row);
212:                            found = true;
213:                        }
214:                    } while (!found);
215:                    return found;
216:                }
217:                return true;
218:            }
219:
220:            boolean nextExcept() throws SQLException, IOException {
221:                if (!all || duplicateCount-- <= 0) {
222:                    boolean found = false;
223:                    do {
224:                        if (!bc.next())
225:                            return false;
226:                        byte[] data = bc.getValBuf();
227:                        int acnt = TempTableMerge.getCount(data, 0);
228:                        int bcnt = TempTableMerge.getCount(data, 1);
229:                        duplicateCount = all ? (acnt - bcnt)
230:                                : (acnt > 0 && bcnt == 0) ? 1 : 0;
231:                        if (duplicateCount-- > 0) {
232:                            tempTable.getRow(data, row);
233:                            found = true;
234:                        }
235:                    } while (!found);
236:                    return found;
237:                }
238:                return true;
239:            }
240:
241:            /**
242:             * On close, we release the resources.
243:             */
244:            public void close() throws SQLException {
245:                try {
246:                    if (bc != null)
247:                        bc.release();
248:                } finally {
249:                    bc = null;
250:                    try {
251:                        if (tempTable != null)
252:                            tempTable.release();
253:                    } catch (IOException e2) {
254:                        throw DbException.wrapThrowable(e2);
255:                    } finally {
256:                        tempTable = null;
257:                    }
258:                }
259:            }
260:        }
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