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Java > Open Source Codes > mondrian > rolap > RolapNativeTopCount


1 /*
2 // This software is subject to the terms of the Common Public License
3 // Agreement, available at the following URL:
4 // http://www.opensource.org/licenses/cpl.html.
5 // Copyright (C) 2004-2005 TONBELLER AG
6 // All Rights Reserved.
7 // You must accept the terms of that agreement to use this software.
8 */
9 package mondrian.rolap;
10
11 import java.sql.Connection JavaDoc;
12 import java.sql.SQLException JavaDoc;
13 import java.util.ArrayList JavaDoc;
14 import java.util.List JavaDoc;
15 import java.util.Map JavaDoc;
16
17 import javax.sql.DataSource JavaDoc;
18
19 import mondrian.olap.*;
20 import mondrian.rolap.sql.SqlQuery;
21 import mondrian.rolap.sql.TupleConstraint;
22 import mondrian.rolap.sql.SqlQuery.Dialect;
23
24 /**
25  * Computes a TopCount in SQL.
26  *
27  * @author av
28  * @since Nov 21, 2005
29  * @version $Id: //open/mondrian/src/main/mondrian/rolap/RolapNativeTopCount.java#16 $
30  */
31 public class RolapNativeTopCount extends RolapNativeSet {
32
33     boolean ascending;
34
35     public RolapNativeTopCount() {
36         super.setEnabled(MondrianProperties.instance().EnableNativeTopCount.get());
37     }
38
39     class TopCountConstraint extends SetConstraint {
40         String JavaDoc orderByExpr;
41
42         public TopCountConstraint(CrossJoinArg[] args, RolapEvaluator evaluator, String JavaDoc orderByExpr) {
43             super(args, evaluator, true);
44             this.orderByExpr = orderByExpr;
45         }
46
47         /**
48          * we alwas need to join the fact table because we want to evalutate
49          * the top count expression which involves a fact.
50          */
51         protected boolean isJoinRequired() {
52             return true;
53         }
54
55         public void addConstraint(
56             SqlQuery sqlQuery,
57             Map JavaDoc<RolapLevel, RolapStar.Column> levelToColumnMap) {
58             if (orderByExpr != null) {
59                 Dialect dialect = sqlQuery.getDialect();
60                 if (dialect.requiresOrderByAlias()) {
61                     String JavaDoc alias = sqlQuery.nextColumnAlias();
62                     alias = dialect.quoteIdentifier(alias);
63                     sqlQuery.addSelect(orderByExpr, alias);
64                     sqlQuery.addOrderBy(alias, ascending, true, false);
65                 } else {
66                     sqlQuery.addOrderBy(orderByExpr, ascending, true, false);
67                 }
68             }
69             super.addConstraint(sqlQuery, levelToColumnMap);
70         }
71
72         public Object JavaDoc getCacheKey() {
73             List JavaDoc<Object JavaDoc> key = new ArrayList JavaDoc<Object JavaDoc>();
74             key.add(super.getCacheKey());
75             key.add(orderByExpr);
76             key.add(ascending);
77             return key;
78         }
79     }
80
81     protected boolean isStrict() {
82         return true;
83     }
84
85     NativeEvaluator createEvaluator(RolapEvaluator evaluator, FunDef fun, Exp[] args) {
86         if (!isEnabled())
87             return null;
88         if (!TopCountConstraint.isValidContext(evaluator)) {
89             return null;
90         }
91
92         // is this "TopCount(<set>, <count>, [<numeric expr>])"
93 String JavaDoc funName = fun.getName();
94         if ("TopCount".equalsIgnoreCase(funName)) {
95             ascending = false;
96         } else if ("BottomCount".equalsIgnoreCase(funName)) {
97             ascending = true;
98         } else {
99             return null;
100         }
101         if (args.length < 2 || args.length > 3) {
102             return null;
103         }
104         // extract the set expression
105 CrossJoinArg[] cargs = checkCrossJoinArg(args[0]);
106         if (cargs == null) {
107             return null;
108         }
109         if (isPreferInterpreter(cargs)) {
110             return null;
111         }
112
113         // extract count
114 if (!(args[1] instanceof Literal)) {
115             return null;
116         }
117         int count = ((Literal) args[1]).getIntValue();
118
119         // extract "order by" expression
120 SchemaReader schemaReader = evaluator.getSchemaReader();
121         DataSource JavaDoc ds = schemaReader.getDataSource();
122
123         // generate the ORDER BY Clause
124 SqlQuery sqlQuery = SqlQuery.newQuery(ds, "NativeTopCount");
125         RolapNativeSql sql = new RolapNativeSql(sqlQuery);
126         String JavaDoc orderByExpr = null;
127         if (args.length == 3) {
128             orderByExpr = sql.generateTopCountOrderBy(args[2]);
129             if (orderByExpr == null) {
130                 return null;
131             }
132         }
133         LOGGER.debug("using native topcount");
134         evaluator = overrideContext(evaluator, cargs, sql.getStoredMeasure());
135
136         TupleConstraint constraint = new TopCountConstraint(cargs, evaluator, orderByExpr);
137         SetEvaluator sev = new SetEvaluator(cargs, schemaReader, constraint);
138         sev.setMaxRows(count);
139         return sev;
140     }
141 }
142
143 // End RolapNativeTopCount.java
144
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