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6<title>Berkeley DB: Bulk Retrieval API</title>
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13<b>Bulk Retrieval API</b>
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21<b><pre>
22#include &lt;db_cxx.h&gt;
23<p>
24class DbMultipleDataIterator
25{
26public:
27	DbMultipleDataIterator(const Dbt &dbt);
28<p>
29	bool next(Dbt &data);
30};
31<p>
32class DbMultipleKeyDataIterator
33{
34public:
35	DbMultipleKeyDataIterator(const Dbt &dbt);
36<p>
37	bool next(Dbt &key, Dbt &data);
38};
39<p>
40class DbMultipleRecnoDataIterator
41{
42public:
43	DbMultipleRecnoDataIterator(const Dbt &dbt);
44<p>
45	bool next(db_recno_t &key, Dbt &data);
46};
47</pre></b>
48<hr size=1 noshade>
49<b>Description: Bulk Retrieval API</b>
50<p>If either of the <a href="../api_cxx/dbc_get.html#DB_MULTIPLE">DB_MULTIPLE</a> or <a href="../api_cxx/dbc_get.html#DB_MULTIPLE_KEY">DB_MULTIPLE_KEY</a> flags
51were specified to the <a href="../api_cxx/db_get.html">Db::get</a> or <a href="../api_cxx/dbc_get.html">Dbc::get</a> method, the data
52<a href="../api_cxx/dbt_class.html">Dbt</a> returned by those interfaces will refer to a buffer that
53is filled with data.  Access to that data is through the following
54classes.</p>
55<p>All instances of the bulk retrieval classes may be used only once, and
56to traverse the bulk retrieval buffer in the forward direction only.
57However, they are nondestructive, so multiple iterators can be
58instantiated and used on the same returned data <a href="../api_cxx/dbt_class.html">Dbt</a>.</p>
59<hr size=1 noshade>
60<b>Description: DbMultipleIterator</b>
61<p>The <a href="../api_cxx/dbt_bulk_class.html">DbMultipleIterator</a> is a shared package-private base class
62for the three types of bulk-return Iterator; it should never be
63instantiated directly, but it handles the functionality shared by its
64subclasses.</p>
65<hr size=1 noshade>
66<b>Description: DbMultipleDataIterator</b>
67<p>The DbMultipleDataIterator class is used to iterate through data
68returned using the <a href="../api_cxx/dbc_get.html#DB_MULTIPLE">DB_MULTIPLE</a> flag from a database belonging
69to any access method.</p>
70<p>The constructor takes the data <a href="../api_cxx/dbt_class.html">Dbt</a> returned by the call to
71<a href="../api_cxx/db_get.html">Db::get</a> or <a href="../api_cxx/dbc_get.html">Dbc::get</a> that used the <a href="../api_cxx/dbc_get.html#DB_MULTIPLE">DB_MULTIPLE</a>
72flag.</p>
73<b>Parameters</b> <br>
74 <b>dbt</b><ul compact><li>The <b>dbt</b> parameter is a data <a href="../api_cxx/dbt_class.html">Dbt</a> returned by the call to
75<a href="../api_cxx/db_get.html">Db::get</a> or <a href="../api_cxx/dbc_get.html">Dbc::get</a> that used the <a href="../api_cxx/dbc_get.html#DB_MULTIPLE">DB_MULTIPLE</a>
76flag.</ul>
77<br>
78<hr size=1 noshade>
79<b>Description: DbMultipleDataIterator.next</b>
80<p>The DbMultipleDataIterator.next method takes a <a href="../api_cxx/dbt_class.html">Dbt</a> that will be
81filled in with a reference to a buffer, a size, and an offset that
82together yield the next data item in the original bulk retrieval buffer.</p>
83<p>The DbMultipleDataIterator.next method returns false if no more data are
84available, and true otherwise.</p>
85<b>Parameters</b> <br>
86 <b>data</b><ul compact><li>The <b>data</b> parameter is a <a href="../api_cxx/dbt_class.html">Dbt</a> that will be filled in with
87a reference to a buffer, a size, and an offset that together yield the
88next data item in the original bulk retrieval buffer.</ul>
89<br>
90<hr size=1 noshade>
91<b>Description: DbMultipleKeyDataIterator</b>
92<p>The DbMultipleKeyDataIterator class is used to iterate through
93data returned using the <a href="../api_cxx/dbc_get.html#DB_MULTIPLE_KEY">DB_MULTIPLE_KEY</a> flag from a database
94belonging to the Btree or Hash access methods.</p>
95<p>The constructor takes the data <a href="../api_cxx/dbt_class.html">Dbt</a> returned by the call to
96<a href="../api_cxx/db_get.html">Db::get</a> or <a href="../api_cxx/dbc_get.html">Dbc::get</a> that used the <a href="../api_cxx/dbc_get.html#DB_MULTIPLE_KEY">DB_MULTIPLE_KEY</a>
97flag.</p>
98<b>Parameters</b> <br>
99 <b>dbt</b><ul compact><li>The <b>dbt</b> parameter is a data <a href="../api_cxx/dbt_class.html">Dbt</a> returned by the call to
100<a href="../api_cxx/db_get.html">Db::get</a> or <a href="../api_cxx/dbc_get.html">Dbc::get</a> that used the <a href="../api_cxx/dbc_get.html#DB_MULTIPLE_KEY">DB_MULTIPLE_KEY</a>
101flag.</ul>
102<br>
103<hr size=1 noshade>
104<b>Description: DbMultipleKeyDataIterator.next</b>
105<p>The DbMultipleKeyDataIterator.next method takes two <a href="../api_cxx/dbt_class.html">Dbt</a>s, one
106for a key and one for a data item, that will each be filled in with a
107reference to a buffer, a size, and an offset that together yield the
108next key and data item in the original bulk retrieval buffer.  The
109DbMultipleKeyDataIterator.next method returns false if no more data are
110available, and true otherwise.</p>
111<p>The DbMultipleKeyDataIterator.next method returns false if no more data
112are available, and true otherwise.</p>
113<b>Parameters</b> <br>
114 <b>key</b><ul compact><li>The <b>key</b> parameter will be filled in with a reference to a buffer,
115a size, and an offset that yields the next key item in the original bulk
116retrieval buffer.</ul>
117 <b>data</b><ul compact><li>The <b>data</b> parameter will be filled in with a reference to a buffer,
118a size, and an offset that yields the next data item in the original bulk
119retrieval buffer.</ul>
120<br>
121<hr size=1 noshade>
122<b>Description: DbMultipleRecnoDataIterator</b>
123<p>This class is used to iterate through data returned using the
124<a href="../api_cxx/dbc_get.html#DB_MULTIPLE_KEY">DB_MULTIPLE_KEY</a> flag from a database belonging to the Recno or
125Queue access methods.</p>
126<p>The constructor takes the data <a href="../api_cxx/dbt_class.html">Dbt</a> returned by the call to
127<a href="../api_cxx/db_get.html">Db::get</a> or <a href="../api_cxx/dbc_get.html">Dbc::get</a> that used the <a href="../api_cxx/dbc_get.html#DB_MULTIPLE_KEY">DB_MULTIPLE_KEY</a>
128flag.</p>
129<b>Parameters</b> <br>
130 <b>dbt</b><ul compact><li>The <b>dbt</b> parameter is a data <a href="../api_cxx/dbt_class.html">Dbt</a> returned by the call to
131<a href="../api_cxx/db_get.html">Db::get</a> or <a href="../api_cxx/dbc_get.html">Dbc::get</a> that used the <a href="../api_cxx/dbc_get.html#DB_MULTIPLE_KEY">DB_MULTIPLE_KEY</a>
132flag.</ul>
133<br>
134<hr size=1 noshade>
135<b>Description: DbMultipleRecnoDataIterator.next</b>
136The DbMultipleRecnoDataIterator.next method takes a <b>db_recno_t</b>
137for the key and a <a href="../api_cxx/dbt_class.html">Dbt</a> for a data item, which will be filled in
138with a pointer to a buffer and a size.  Together they yield the next key
139and data item in the original bulk retrieval buffer.
140<p>The DbMultipleRecnoDataIterator.next method returns false if no more
141data are available, and true otherwise.</p>
142<b>Parameters</b> <br>
143 <b>key</b><ul compact><li>The <b>key</b> parameter will be filled in with a reference to a
144buffer, a size, and an offset that yields the next key item in the
145original bulk retrieval buffer.</ul>
146 <b>data</b><ul compact><li>The <b>data</b> parameter will be filled in with a reference to a
147buffer, a size, and an offset that yields the next data item in the
148original bulk retrieval buffer.</ul>
149<br>
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