View


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30  
31  
32  package org.hsqldb;
33  
34  import org.hsqldb.HsqlNameManager.HsqlName;
35  import org.hsqldb.lib.HsqlArrayList;
36  import org.hsqldb.lib.Iterator;
37  
38  // fredt@users 20020420 - patch523880 by leptipre@users - VIEW support - modified
39  // fredt@users 20031227 - remimplementated as compiled query
40  
41  /**
42   * Represents an SQL VIEW based on a SELECT statement.
43   *
44   * @author leptipre@users
45   * @author fredt@users
46   * @version 1.8.0
47   * @since 1.7.0
48   */
49  class View extends Table {
50  
51      Select             viewSelect;
52      SubQuery           viewSubQuery;
53      private String       statement;
54      private HsqlName[] colList;
55  
56      /** schema at the time of compilation */
57      HsqlName compileTimeSchema;
58  
59      /**
60       * List of subqueries in this view in order of materialization. Last
61       * element is the view itself.
62       */
63      SubQuery[] viewSubqueries;
64  
65      /**
66       * Constructor.
67       * @param Session
68       * @param db database
69       * @param name HsqlName of the view
70       * @param definition SELECT statement of the view
71       * @param columns array of HsqlName column names
72       * @throws HsqlException
73       */
74      View(Session session, Database db, HsqlName name, String   definition,
75              HsqlName[] columns) throws HsqlException {
76  
77          super(db, name, VIEW);
78  
79          isReadOnly        = true;
80          colList           = columns;
81          statement         = trimStatement(definition);
82          compileTimeSchema = session.getSchemaHsqlName(null);
83  
84          compile(session);
85  
86          HsqlName[] schemas = getSchemas();
87  
88          for (int i = 0; i < schemas.length; i++) {
89              if (db.schemaManager.isSystemSchema(schemas[i])) {
90                  continue;
91              }
92  
93              if (!schemas[i].equals(name.schema)) {
94                  throw Trace.error(Trace.INVALID_SCHEMA_NAME_NO_SUBCLASS);
95              }
96          }
97      }
98  
99      /**
100      * Returns the SELECT statement trimmed of any terminating SQL
101      * whitespace, separators or SQL comments.
102      */
103     static String   trimStatement(String   s) throws HsqlException {
104 
105         int       position;
106         String      str;
107         Tokenizer tokenizer = new Tokenizer(s);
108 
109         // fredt@users - this establishes the end of the actual statement
110         // to get rid of any end semicolon or comment line after the end
111         // of statement
112         do {
113             position = tokenizer.getPosition();
114             str      = tokenizer.getString();
115         } while (str.length() != 0 || tokenizer.wasValue());
116 
117         return s.substring(0, position).trim();
118     }
119 
120     /**
121      * Compiles the SELECT statement and sets up the columns.
122      */
123     void compile(Session session) throws HsqlException {
124 
125         // create the working table
126         Parser p = new Parser(session, this.database,
127                               new Tokenizer(statement));
128         int brackets = p.parseOpenBracketsSelect();
129 
130         viewSubQuery = p.parseSubquery(brackets, colList, true,
131                                        Expression.VIEW);
132 
133         p.setAsView(this);
134 
135         viewSubqueries = p.getSortedSubqueries();
136         viewSelect     = viewSubQuery.select;
137 
138         viewSelect.prepareResult(session);
139 
140         Result.ResultMetaData metadata = viewSelect.resultMetaData;
141         int                   columns  = viewSelect.iResultLen;
142 
143         if (super.columnCount == 0) {
144 
145             // do not add columns at recompile time
146             super.addColumns(metadata, columns);
147         }
148     }
149 
150     /**
151      * Returns the SELECT statement for the view.
152      */
153     String   getStatement() {
154         return statement;
155     }
156 
157     /**
158      * Overridden to disable SET TABLE READONLY DDL for View objects.
159      */
160     void setDataReadOnly(boolean value) throws HsqlException {
161         throw Trace.error(Trace.NOT_A_TABLE);
162     }
163 
164     /**
165      * Returns list of schemas
166      */
167     HsqlName[] getSchemas() {
168 
169         HsqlArrayList list = new HsqlArrayList();
170 
171         for (int i = 0; i < viewSubqueries.length; i++) {
172             Select select = viewSubqueries[i].select;
173 
174             for (; select != null; select = select.unionSelect) {
175                 TableFilter[] tfilter = select.tFilter;
176 
177                 for (int j = 0; j < tfilter.length; j++) {
178                     list.add(tfilter[j].filterTable.tableName.schema);
179                 }
180             }
181         }
182 
183         return (HsqlName[]) list.toArray(new HsqlName[list.size()]);
184     }
185 
186     boolean hasView(View view) {
187 
188         if (view == this) {
189             return false;
190         }
191 
192         for (int i = 0; i < viewSubqueries.length; i++) {
193             if (viewSubqueries[i].view == view) {
194                 return true;
195             }
196         }
197 
198         return false;
199     }
200 
201     /**
202      * Returns true if the view references any column of the named table.
203      */
204     boolean hasTable(Table table) {
205 
206         for (int i = 0; i < viewSubqueries.length; i++) {
207             Select select = viewSubqueries[i].select;
208 
209             for (; select != null; select = select.unionSelect) {
210                 TableFilter[] tfilter = select.tFilter;
211 
212                 for (int j = 0; j < tfilter.length; j++) {
213                     if (table.equals(tfilter[j].filterTable.tableName)) {
214                         return true;
215                     }
216                 }
217             }
218         }
219 
220         return false;
221     }
222 
223     /**
224      * Returns true if the view references the named column of the named table,
225      * otherwise false.
226      */
227     boolean hasColumn(Table table, String   colname) {
228 
229         if (hasTable(table)) {
230             Expression.Collector coll = new Expression.Collector();
231 
232             coll.addAll(viewSubqueries[viewSubqueries.length - 1].select,
233                         Expression.COLUMN);
234 
235             Iterator it = coll.iterator();
236 
237             for (; it.hasNext(); ) {
238                 Expression e = (Expression) it.next();
239 
240                 if (colname.equals(e.getBaseColumnName())
241                         && table.equals(e.getTableHsqlName())) {
242                     return true;
243                 }
244             }
245         }
246 
247         return false;
248     }
249 
250     /**
251      * Returns true if the view references the named SEQUENCE,
252      * otherwise false.
253      */
254     boolean hasSequence(NumberSequence sequence) {
255 
256         Expression.Collector coll = new Expression.Collector();
257 
258         coll.addAll(viewSubqueries[viewSubqueries.length - 1].select,
259                     Expression.SEQUENCE);
260 
261         Iterator it = coll.iterator();
262 
263         for (; it.hasNext(); ) {
264             Expression e = (Expression) it.next();
265 
266             if (e.valueData == sequence) {
267                 return true;
268             }
269         }
270 
271         return false;
272     }
273 }
274
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