001    /**
002     * Copyright (c) 2000-2013 Liferay, Inc. All rights reserved.
003     *
004     * This library is free software; you can redistribute it and/or modify it under
005     * the terms of the GNU Lesser General Public License as published by the Free
006     * Software Foundation; either version 2.1 of the License, or (at your option)
007     * any later version.
008     *
009     * This library is distributed in the hope that it will be useful, but WITHOUT
010     * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
011     * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
012     * details.
013     */
014    
015    package com.liferay.portal.dao.orm.hibernate;
016    
017    import com.liferay.portal.kernel.util.StringBundler;
018    import com.liferay.portal.kernel.util.StringPool;
019    import com.liferay.portal.kernel.util.StringUtil;
020    
021    /**
022     * @author Shepherd Ching
023     * @author Jian Cao
024     * @author Laszlo Csontos
025     */
026    public class DB2Dialect extends org.hibernate.dialect.DB2Dialect {
027    
028            public DB2Dialect() {
029                    super();
030    
031                    registerKeyword("for");
032                    registerKeyword("optimize");
033            }
034    
035            @Override
036            public String getForUpdateString() {
037                    return " for read only with rs use and keep exclusive locks";
038            }
039    
040            @Override
041            public String getLimitString(String sql, int offset, int limit) {
042                    boolean hasOffset = false;
043    
044                    if ((offset > 0) || forceLimitUsage()) {
045                            hasOffset = true;
046                    }
047    
048                    StringBundler sb = null;
049    
050                    if (hasOffset) {
051                            sb = new StringBundler(11);
052                    }
053                    else {
054                            sb = new StringBundler(5);
055                    }
056    
057                    if (!hasOffset) {
058                            addQueryForLimitedRows(sb, sql, limit);
059                            addOptimizeForLimitedRows(sb, limit);
060    
061                            return sb.toString();
062                    }
063    
064                    // Outer query
065    
066                    sb.append("SELECT outerQuery.* FROM (");
067                    sb.append("SELECT ROW_NUMBER() OVER() AS rowNumber_, ");
068    
069                    // Inner query
070    
071                    sb.append("innerQuery.* FROM (");
072    
073                    addQueryForLimitedRows(sb, sql, limit);
074    
075                    sb.append(") AS innerQuery");
076    
077                    // Offset
078    
079                    sb.append(") AS outerQuery WHERE rowNumber_ > ");
080                    sb.append(offset);
081    
082                    addOptimizeForLimitedRows(sb, limit);
083    
084                    return sb.toString();
085            }
086    
087            @Override
088            public boolean supportsVariableLimit() {
089                    return _SUPPORTS_VARIABLE_LIMIT;
090            }
091    
092            protected void addOptimizeForLimitedRows(StringBundler sb, int limit) {
093                    sb.append(StringPool.SPACE);
094                    sb.append(
095                            StringUtil.replace(
096                                    _SQL_OPTIMIZE_FOR_LIMITED_ROWS, "[$LIMIT$]",
097                                    String.valueOf(limit)));
098            }
099    
100            protected void addQueryForLimitedRows(
101                    StringBundler sb, String sql, int limit) {
102    
103                    sb.append(sql);
104                    sb.append(StringPool.SPACE);
105                    sb.append(
106                            StringUtil.replace(
107                                    _SQL_FETCH_FIRST_LIMITED_ROWS_ONLY, "[$LIMIT$]",
108                                    String.valueOf(limit)));
109            }
110    
111            private static final String _SQL_FETCH_FIRST_LIMITED_ROWS_ONLY =
112                    "FETCH FIRST [$LIMIT$] ROWS ONLY";
113    
114            private static final String _SQL_OPTIMIZE_FOR_LIMITED_ROWS =
115                    "OPTIMIZE FOR [$LIMIT$] ROWS";
116    
117            private static final boolean _SUPPORTS_VARIABLE_LIMIT = false;
118    
119    }