01: /*
02:
03: Derby - Class org.apache.derby.impl.sql.compile.CountAggregateDefinition
04:
05: Licensed to the Apache Software Foundation (ASF) under one or more
06: contributor license agreements. See the NOTICE file distributed with
07: this work for additional information regarding copyright ownership.
08: The ASF licenses this file to you under the Apache License, Version 2.0
09: (the "License"); you may not use this file except in compliance with
10: the License. You may obtain a copy of the License at
11:
12: http://www.apache.org/licenses/LICENSE-2.0
13:
14: Unless required by applicable law or agreed to in writing, software
15: distributed under the License is distributed on an "AS IS" BASIS,
16: WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17: See the License for the specific language governing permissions and
18: limitations under the License.
19:
20: */
21:
22: package org.apache.derby.impl.sql.compile;
23:
24: import org.apache.derby.iapi.sql.conn.LanguageConnectionContext;
25: import org.apache.derby.iapi.types.DataTypeDescriptor;
26:
27: import org.apache.derby.impl.sql.execute.CountAggregator;
28:
29: import org.apache.derby.catalog.TypeDescriptor;
30:
31: import org.apache.derby.iapi.reference.ClassName;
32:
33: /**
34: * Defintion for the COUNT()/COUNT(*) aggregates.
35: *
36: * @author jamie
37: */
38: public class CountAggregateDefinition implements AggregateDefinition {
39: /**
40: * Niladic constructor. Does nothing. For ease
41: * Of use, only.
42: */
43: public CountAggregateDefinition() {
44: super ();
45: }
46:
47: /**
48: * Determines the result datatype. We can run
49: * count() on anything, and it always returns a
50: * INTEGER (java.lang.Integer).
51: *
52: * @param inputType the input type, either a user type or a java.lang object
53: *
54: * @return the output Class (null if cannot operate on
55: * value expression of this type.
56: */
57: public final TypeDescriptor getAggregator(TypeDescriptor inputType,
58: StringBuffer aggregatorClass) {
59: aggregatorClass.append(ClassName.CountAggregator);
60: /*
61: ** COUNT never returns NULL
62: */
63: return DataTypeDescriptor.getBuiltInDataTypeDescriptor(
64: java.sql.Types.INTEGER, false);
65: }
66:
67: }
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