This repository has been archived by the owner on Jun 29, 2021. It is now read-only.
-
Notifications
You must be signed in to change notification settings - Fork 151
/
OffsetFetchQueryRewriter.java
79 lines (69 loc) · 3.22 KB
/
OffsetFetchQueryRewriter.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
/**
* Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE
* file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*/
package org.apache.metamodel.jdbc.dialects;
import org.apache.metamodel.jdbc.JdbcDataContext;
import org.apache.metamodel.query.Query;
/**
* Query rewriter for databases that support OFFSET and FETCH keywords for max
* rows and first row properties.
*/
public abstract class OffsetFetchQueryRewriter extends DefaultQueryRewriter {
private final String _databaseProductName;
private final int _databaseSupportedVersion;
private final boolean _fetchNeedsOffsetAndOrderBy;
public OffsetFetchQueryRewriter(final JdbcDataContext dataContext, final int minSupportedVersion,
final boolean fetchNeedsOrderBy) {
super(dataContext);
_databaseProductName = dataContext.getDatabaseProductName();
_databaseSupportedVersion = minSupportedVersion;
_fetchNeedsOffsetAndOrderBy = fetchNeedsOrderBy;
}
@Override
public boolean isFirstRowSupported(final Query query) {
return isSupportedVersion(_databaseProductName, _databaseSupportedVersion) && !query.getOrderByClause()
.isEmpty();
}
@Override
public boolean isMaxRowsSupported() {
return isSupportedVersion(_databaseProductName, _databaseSupportedVersion);
}
/**
* {@inheritDoc}
*
* If the Max rows and First row property of the query is set, then we
* will use the database's "OFFSET i ROWS FETCH NEXT j ROWS ONLY" construct.
*/
@Override
public String rewriteQuery(final Query query) {
final boolean hasOrderBy = !query.getOrderByClause().isEmpty();
String queryString = super.rewriteQuery(query);
if (isSupportedVersion(_databaseProductName, _databaseSupportedVersion) && (query.getMaxRows() != null
|| query.getFirstRow() != null)) {
final Integer maxRows = query.getMaxRows();
Integer firstRow = query.getFirstRow();
if (!_fetchNeedsOffsetAndOrderBy || hasOrderBy) {
if (firstRow != null) {
queryString = queryString + " OFFSET " + (firstRow - 1) + " ROWS";
} else if (_fetchNeedsOffsetAndOrderBy) {
// TOP should do it.
return queryString;
}
if (maxRows != null) {
queryString = queryString.replaceAll(" TOP [0-9]+", "");
queryString += " FETCH NEXT " + maxRows + " ROWS ONLY";
}
}
}
return queryString;
}
}