hunt.database.base.Cursor source code

1 /*
2  * Copyright (C) 2019, HuntLabs
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  *
16  */
17 
18 module hunt.database.base.Cursor;
19 
20 import hunt.database.base.AsyncResult;
21 import hunt.database.base.Common;
22 import hunt.database.base.RowSet;
23 
24 import hunt.logging;
25 
26 
27 
28 /**
29  * A cursor that reads progressively rows from the database, it is useful for reading very large result sets.
30  */
31 interface Cursor {
32 
33     /**
34      * Read rows from the cursor, the result is provided asynchronously to the {@code handler}.
35      *
36      * @param count the amount of rows to read
37      * @param handler the handler for the result
38      */
39     void read(int count, RowSetHandler handler);
40 
41     /**
42      * Returns {@code true} when the cursor has results in progress and the {@link #read} should be called to retrieve
43      * them.
44      *
45      * @return whether the cursor has more results,
46      */
47     bool hasMore();
48 
49     /**
50      * Release the cursor.
51      * <p/>
52      * It should be called for prepared queries executed with a fetch size.
53      */
54     final void close() {
55         close((ar) {
56             warning("do nothing...");
57         });
58     }
59 
60     /**
61      * Like {@link #close()} but with a {@code completionHandler} called when the cursor has been released.
62      */
63     void close(AsyncVoidHandler completionHandler);
64 
65 }