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org.apache.torque.util.JoinBuilder |
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1 | package org.apache.torque.util; |
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2 | ||
3 | /* |
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4 | * Licensed to the Apache Software Foundation (ASF) under one |
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5 | * or more contributor license agreements. See the NOTICE file |
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6 | * distributed with this work for additional information |
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7 | * regarding copyright ownership. The ASF licenses this file |
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8 | * to you under the Apache License, Version 2.0 (the |
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9 | * "License"); you may not use this file except in compliance |
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10 | * with the License. You may obtain a copy of the License at |
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11 | * |
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12 | * http://www.apache.org/licenses/LICENSE-2.0 |
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13 | * |
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14 | * Unless required by applicable law or agreed to in writing, |
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15 | * software distributed under the License is distributed on an |
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16 | * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
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17 | * KIND, either express or implied. See the License for the |
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18 | * specific language governing permissions and limitations |
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19 | * under the License. |
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20 | */ |
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21 | ||
22 | import java.util.List; |
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23 | ||
24 | import org.apache.torque.TorqueException; |
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25 | import org.apache.torque.adapter.DB; |
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26 | import org.apache.torque.map.DatabaseMap; |
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27 | ||
28 | /** |
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29 | * Factored out code that is used to generate Join Code. This code comes |
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30 | * from BasePeer and is put here to reduce complexity in the BasePeer class. |
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31 | * You should not use the methods here directly! |
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32 | * |
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33 | * @author <a href="mailto:fischer@seitenbau.de">Thomas Fischer</a> |
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34 | * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a> |
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35 | * @version $Id: JoinBuilder.java 476550 2006-11-18 16:08:37Z tfischer $ |
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36 | */ |
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37 | public final class JoinBuilder |
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38 | { |
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39 | /** |
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40 | * Private constructor to prevent initialisation. |
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41 | * |
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42 | * Class contains only static methods and should therefore not be |
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43 | * instantiated. |
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44 | */ |
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45 | private JoinBuilder() |
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46 | 0 | { |
47 | 0 | } |
48 | ||
49 | /** |
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50 | * adds the Joins from the criteria to the query |
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51 | * @param criteria the criteria from which the Joins are taken |
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52 | * @param query the query to which the Joins should be added |
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53 | * @throws TorqueException if the Joins can not be processed |
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54 | */ |
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55 | public static void processJoins( |
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56 | final DB db, |
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57 | final DatabaseMap dbMap, |
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58 | final Criteria criteria, |
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59 | final Query query) |
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60 | throws TorqueException |
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61 | { |
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62 | 240 | List criteriaJoins = criteria.getJoins(); |
63 | ||
64 | 240 | if (criteriaJoins == null) |
65 | { |
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66 | 224 | return; |
67 | } |
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68 | ||
69 | 16 | UniqueList queryFromClause = query.getFromClause(); |
70 | 16 | UniqueList queryWhereClause = query.getWhereClause(); |
71 | ||
72 | 32 | for (int i = 0; i < criteriaJoins.size(); i++) |
73 | { |
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74 | 16 | Criteria.Join join = (Criteria.Join) criteriaJoins.get(i); |
75 | 16 | String leftColumn = join.getLeftColumn(); |
76 | 16 | String rightColumn = join.getRightColumn(); |
77 | ||
78 | // check if the column names make sense |
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79 | 16 | if (leftColumn.indexOf('.') == -1) |
80 | { |
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81 | 0 | SQLBuilder.throwMalformedColumnNameException("join", leftColumn); |
82 | } |
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83 | 16 | if (rightColumn.indexOf('.') == -1) |
84 | { |
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85 | 0 | SQLBuilder.throwMalformedColumnNameException("join", rightColumn); |
86 | } |
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87 | ||
88 | // get the table names |
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89 | // (and the alias names for them if necessary)) |
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90 | // Also check whether a case insensitive comparison is needed |
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91 | 16 | int dot = leftColumn.lastIndexOf('.'); |
92 | 16 | String leftTableName = leftColumn.substring(0, dot); |
93 | ||
94 | 16 | leftTableName = |
95 | SQLBuilder.getTableNameForFromClause(leftTableName, criteria); |
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96 | ||
97 | 16 | dot = rightColumn.lastIndexOf('.'); |
98 | 16 | String rightTableName = rightColumn.substring(0, dot); |
99 | 16 | String dbTableName |
100 | = criteria.getTableForAlias(rightTableName); |
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101 | ||
102 | 16 | if (dbTableName == null) |
103 | { |
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104 | 0 | dbTableName = rightTableName; |
105 | } |
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106 | ||
107 | 16 | String columnName = rightColumn.substring( |
108 | dot + 1, |
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109 | rightColumn.length()); |
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110 | ||
111 | 16 | boolean ignoreCase = (criteria.isIgnoreCase() |
112 | && (dbMap |
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113 | .getTable(dbTableName) |
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114 | .getColumn(columnName) |
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115 | .getType() |
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116 | instanceof String)); |
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117 | ||
118 | 16 | rightTableName = SQLBuilder.getTableNameForFromClause( |
119 | rightTableName, criteria); |
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120 | ||
121 | // now check the join type and add the join to the |
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122 | // appropriate places in the query |
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123 | 16 | SqlEnum joinType = join.getJoinType(); |
124 | ||
125 | 16 | if (joinType == null) |
126 | { |
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127 | // Do not treat join as explicit join, but add |
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128 | // the join condition to the where clauses |
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129 | 16 | if (!SQLBuilder.fromClauseContainsTableName( |
130 | queryFromClause, |
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131 | leftTableName)) |
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132 | { |
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133 | 16 | Query.FromElement fromElement |
134 | = new Query.FromElement( |
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135 | leftTableName, null, class="keyword">null); |
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136 | 16 | queryFromClause.add(fromElement); |
137 | } |
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138 | 16 | if (!SQLBuilder.fromClauseContainsTableName( |
139 | queryFromClause, |
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140 | rightTableName)) |
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141 | { |
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142 | 16 | Query.FromElement fromElement |
143 | = new Query.FromElement( |
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144 | rightTableName, null, class="keyword">null); |
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145 | 16 | queryFromClause.add(fromElement); |
146 | } |
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147 | 16 | queryWhereClause.add( |
148 | SqlExpression.buildInnerJoin( |
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149 | leftColumn, rightColumn, ignoreCase, db)); |
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150 | 16 | } |
151 | else |
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152 | { |
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153 | // check whether the order of the join must be "reversed" |
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154 | // This if the case if the fromClause already contains |
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155 | // rightTableName |
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156 | ||
157 | 0 | if (!SQLBuilder.fromClauseContainsTableName( |
158 | queryFromClause, |
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159 | rightTableName)) |
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160 | { |
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161 | 0 | if (!SQLBuilder.fromClauseContainsTableName( |
162 | queryFromClause, |
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163 | leftTableName)) |
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164 | { |
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165 | 0 | Query.FromElement fromElement |
166 | = new Query.FromElement( |
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167 | leftTableName, null, class="keyword">null); |
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168 | 0 | queryFromClause.add(fromElement); |
169 | } |
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170 | ||
171 | 0 | Query.FromElement fromElement |
172 | = new Query.FromElement( |
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173 | rightTableName, joinType, |
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174 | SqlExpression.buildInnerJoin( |
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175 | leftColumn, rightColumn, |
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176 | ignoreCase, db)); |
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177 | 0 | queryFromClause.add(fromElement); |
178 | 0 | } |
179 | else |
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180 | { |
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181 | 0 | if (SQLBuilder.fromClauseContainsTableName( |
182 | queryFromClause, |
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183 | leftTableName)) |
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184 | { |
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185 | // We cannot add an explicit join if both tables |
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186 | // are alredy present in the from clause |
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187 | 0 | throw new TorqueException( |
188 | "Unable to create a " + joinType |
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189 | + "because both table names " |
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190 | + leftTableName + " and " + rightTableName |
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191 | + " are already in use. " |
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192 | + "Try to create an(other) alias."); |
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193 | } |
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194 | // now add the join in reverse order |
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195 | // rightTableName must not be added |
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196 | // because it is already present |
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197 | 0 | Query.FromElement fromElement |
198 | = new Query.FromElement( |
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199 | leftTableName, reverseJoinType(joinType), |
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200 | SqlExpression.buildInnerJoin( |
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201 | rightColumn, leftColumn, |
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202 | ignoreCase, db)); |
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203 | 0 | queryFromClause.add(fromElement); |
204 | } |
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205 | } |
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206 | } |
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207 | 16 | } |
208 | ||
209 | /** |
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210 | * returns the reversed Join type, i.e. the join type which would produce |
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211 | * the same result if also the joined tables were exchanged: |
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212 | * Example:<br /> |
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213 | * table_a left join table_b <br /> |
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214 | * produces the same result as <br /> |
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215 | * table_b right join table_a<br /> |
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216 | * So "left join" is the reverse of "right join" |
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217 | * @param joinType the join type to be reversed |
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218 | * @return the reversed join type |
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219 | */ |
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220 | private static SqlEnum reverseJoinType(final SqlEnum joinType) |
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221 | { |
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222 | 0 | if (SqlEnum.LEFT_JOIN.equals(joinType)) |
223 | { |
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224 | 0 | return SqlEnum.RIGHT_JOIN; |
225 | } |
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226 | 0 | else if (SqlEnum.RIGHT_JOIN.equals(joinType)) |
227 | { |
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228 | 0 | return SqlEnum.LEFT_JOIN; |
229 | } |
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230 | else |
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231 | { |
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232 | 0 | return joinType; |
233 | } |
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234 | } |
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235 | } |
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