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Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
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<th colspan="3" align="center">Dbc::get()</th>
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<th width="60%" align="center">Chapter 3. 
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<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="dbcget"></a>Dbc::get()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include &lt;db_cxx.h&gt;
int
Dbc::get(Dbt *key, Dbt *data, u_int32_t flags);
int
Dbc::pget(Dbt *key, Dbt *pkey, Dbt *data, u_int32_t flags); </pre>
<p>
The <code class="methodname">Dbc::get()</code> method retrieves key/data pairs from the
database. The address and length of the key are returned in the
object to which <span class="bold"><strong>key</strong></span> refers (except
for the case of the DB_SET flag, in which the <span class="bold"><strong>key</strong></span> object is unchanged), and the address and
length of the data are returned in the object to which <span class="bold"><strong>data</strong></span> refers.
</p>
<p>
When called on a cursor opened on a database that has been made into a
secondary index using the
<a class="xref" href="dbassociate.html" title="Db::associate()">Db::associate()</a> method, the
<code class="methodname">Dbc::get()</code> and <code class="methodname">Dbc::pget()</code>
methods return the key from the
secondary index and the data item from the primary database. In
addition, the <code class="methodname">Dbc::pget()</code> method returns the key from the
primary database. In databases that are not secondary indices, the
<code class="methodname">Dbc::pget()</code> method will always fail.
</p>
<p>
Modifications to the database during a sequential scan will be
reflected in the scan; that is, records inserted behind a cursor will
not be returned while records inserted in front of a cursor will be
returned.
</p>
<p>
In Queue and Recno databases, missing entries (that is, entries that
were never explicitly created or that were created and then deleted)
will be skipped during a sequential scan.
</p>
<p>
Unless otherwise specified, the <code class="methodname">Dbc::get()</code> <span>
<span>
method either returns a non-zero error value or throws an
exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
</span>
</span>
</p>
<p>
If <code class="methodname">Dbc::get()</code> fails for any reason, the state of the cursor will
be unchanged.
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h3 class="title"><a id="id3586060"></a>Parameters</h3>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3586063"></a>key</h4>
Release 5.2.28 on 6/10/2011
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</div>
</div>
</div>
<p>
The key <a class="link" href="dbt.html" title="Chapter 4.  The Dbt Handle">Dbt</a> operated on.
</p>
<p>
If <a class="link" href="dbt.html#dbt_DB_DBT_PARTIAL">DB_DBT_PARTIAL</a>
is set for the Dbt used for this parameter,
and if the <span class="bold"><strong>flags</strong></span> parameter
is set to
<a class="link" href="dbcget.html#dbcget_DB_GET_BOTH">DB_GET_BOTH</a>,
<a class="link" href="dbcget.html#dbcget_DB_GET_BOTH_RANGE">DB_GET_BOTH_RANGE</a>,
<a class="link" href="dbcget.html#dbcget_DB_SET">DB_SET</a>, or
<a class="link" href="dbcget.html#dbcget_DB_SET_RECNO">DB_SET_RECNO</a>,
then this method will fail and return <code class="literal">EINVAL</code>.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3586138"></a>pkey</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
The return key from the primary database.
If
<a class="link" href="dbt.html#dbt_DB_DBT_PARTIAL">DB_DBT_PARTIAL</a>
is set for the Dbt used for this parameter,
then this method will fail and return <code class="literal">EINVAL</code>.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3585966"></a>data</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
The data <a class="link" href="dbt.html" title="Chapter 4.  The Dbt Handle">Dbt</a> operated on.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3586004"></a>flags</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
The <span class="bold"><strong>flags</strong></span> parameter must be set to
one of the following values:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p><a id="dbcget_DB_CURRENT"></a>
<code class="literal">DB_CURRENT</code>
</p>
<p>
Return the key/data pair to which the cursor refers.
</p>
<p>
The <code class="methodname">Dbc::get()</code> method
will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_KEYEMPTY" class="olink">DB_KEYEMPTY</a>
if DB_CURRENT is set and the cursor key/data pair
was deleted.
</p>
</li>
<li>
<p><a id="dbcget_DB_FIRST"></a>
<code class="literal">DB_FIRST</code>
</p>
<p>
The cursor is set to refer to the first key/data
pair of the database, and that pair is returned.
If the first key has duplicate values, the first
data item in the set of duplicates is returned.
</p>
<p>
If the database is a Queue or Recno database,
<code class="methodname">Dbc::get()</code> using the
DB_FIRST flag will ignore any keys that exist but
were never explicitly created by the application,
or were created and later deleted.
</p>
<p>
The <code class="methodname">Dbc::get()</code> method
will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if DB_FIRST is set and the database is empty.
</p>
</li>
<li>
<p><a id="dbcget_DB_GET_BOTH"></a>
<code class="literal">DB_GET_BOTH</code>
</p>
<p>
Move the cursor to the specified key/data pair of
the database. The cursor is positioned to a
key/data pair if both the key and data match the
values provided on the key and data parameters.
</p>
<p>
In all other ways, this flag is identical to the
<a class="link" href="dbcget.html#dbcget_DB_SET">DB_SET</a>
flag.
</p>
<p>
When used with
<code class="methodname">Dbc::pget()</code> on a
secondary index handle, both the secondary and
primary keys must be matched by the secondary and
primary key item in the database. It is an error
to use the DB_GET_BOTH flag with the
<code class="methodname">Dbc::get()</code> version
of this method and a cursor that has been opened on a secondary index
handle.
</p>
</li>
<li>
<p><a id="dbcget_DB_GET_BOTH_RANGE"></a>
<code class="literal">DB_GET_BOTH_RANGE</code>
</p>
<p>
Move the cursor to the specified key/data pair of the
database. The key parameter must be an exact match with a
key in the database. The data item retrieved is the item in
a duplicate set that is the smallest value which is greater than or equal
to the value provided by the data parameter (as determined by the comparison
function). If this flag is specified on a database
configured without sorted duplicate support, the behavior
is identical to the <code class="literal">DB_GET_BOTH</code> flag. Returns the datum
associated with the given key/data pair.
</p>
<p>
In all other ways, this flag is identical to the
<a class="link" href="dbcget.html#dbcget_DB_GET_BOTH">DB_GET_BOTH</a>
flag.
</p>
</li>
<li>
<p><a id="dbcget_DB_GET_RECNO"></a>
<code class="literal">DB_GET_RECNO</code>
</p>
<p>
Return the record number associated with the cursor. The record
number will be returned in <span class="bold"><strong>data</strong></span>, as
described in <a class="link" href="dbt.html" title="Chapter 4.  The Dbt Handle">Dbt</a>. The
<span class="bold"><strong>key</strong></span> parameter is ignored.
</p>
<p>
For DB_GET_RECNO to be specified, the underlying database must be of
type Btree, and it must have been created with the
<a class="link" href="dbset_flags.html#dbset_flags_DB_RECNUM">DB_RECNUM</a>
flag.
</p>
<p>
When called on a cursor opened on a database that has been made into a
secondary index, the <code class="methodname">Dbc::get()</code> and
<code class="methodname">Dbc::pget()</code> methods return the record
number of the primary database in <span class="bold"><strong>data</strong></span>.
In addition, the <code class="methodname">Dbc::pget()</code>
method returns the record number of the secondary index in <span class="bold"><strong>pkey</strong></span>. If either underlying database is not of
type Btree or is not created with the
<a class="link" href="dbset_flags.html#dbset_flags_DB_RECNUM">DB_RECNUM</a>
flag, the out-of-band record number of 0 is returned.
</p>
</li>
<li>
<p><a id="dbcget_DB_JOIN_ITEM"></a>
<code class="literal">DB_JOIN_ITEM</code>
</p>
<p>
Do not use the data value found in all of the cursors as a lookup key
for the primary database, but simply return it in the key parameter
instead. The data parameter is left unchanged.
</p>
<p>
For DB_JOIN_ITEM to be specified, the underlying cursor must have been
returned from the <a class="xref" href="dbjoin.html" title="Db::join()">Db::join()</a> method.
</p>
<p>
This flag is not supported for Heap databases.
</p>
</li>
<li>
<p><a id="dbcget_DB_LAST"></a>
<code class="literal">DB_LAST</code>
</p>
<p>
The cursor is set to refer to the last key/data pair of the database,
and that pair is returned. If the last key has duplicate values, the
last data item in the set of duplicates is returned.
</p>
<p>
If the database is a Queue or Recno database,
<code class="methodname">Dbc::get()</code> using the
DB_LAST flag will ignore any keys that exist but
were never explicitly created by the application,
or were created and later deleted.
</p>
<p>
The <code class="methodname">Dbc::get()</code> method
will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if DB_LAST is set and the database is empty.
</p>
</li>
<li>
<p><a id="dbcget_DB_NEXT"></a>
<code class="literal">DB_NEXT</code>
</p>
<p>
If the cursor is not yet initialized, DB_NEXT is identical to
DB_FIRST. Otherwise, the cursor is moved to the next key/data pair of
the database, and that pair is returned. In the presence of duplicate
key values, the value of the key may not change.
</p>
<p>
If the database is a Queue or Recno database,
<code class="methodname">Dbc::get()</code> using the
DB_NEXT flag will skip any keys that exist but
were never explicitly created by the application,
or those that were created and later deleted.
</p>
<p>
The <code class="methodname">Dbc::get()</code> method
will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if DB_NEXT is set and the cursor is already on the
last record in the database.
</p>
</li>
<li>
<p><a id="dbcget_DB_NEXT_DUP"></a>
<code class="literal">DB_NEXT_DUP</code>
</p>
<p>
If the next key/data pair of the database is a duplicate data record
for the current key/data pair, the cursor is moved to the next
key/data pair of the database, and that pair is returned.
</p>
<p>
The <code class="methodname">Dbc::get()</code> method
will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if DB_NEXT_DUP is set and the next key/data pair
of the database is not a duplicate data record for
the current key/data pair.
</p>
<p>
If using a Heap database, this flag results in this
method returning
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>.
</p>
</li>
<li>
<p><a id="dbcget_DB_NEXT_NODUP"></a>
<code class="literal">DB_NEXT_NODUP</code>
</p>
<p>
If the cursor is not yet initialized, DB_NEXT_NODUP is identical to
DB_FIRST. Otherwise, the cursor is moved to the next non-duplicate
key of the database, and that key/data pair is returned.
</p>
<p>
If the database is a Queue or Recno database,
<code class="methodname">Dbc::get()</code> using the
DB_NEXT_NODUP flag will ignore any keys that exist
but were never explicitly created by the
application, or those that were created and later
deleted.
</p>
<p>
The <code class="methodname">Dbc::get()</code> method
will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if DB_NEXT_NODUP is set and no non-duplicate
key/data pairs exist after the cursor position in
the database.
</p>
<p>
If using a Heap database, this flag is identical to
the <code class="literal">DB_NEXT</code> flag.
</p>
</li>
<li>
<p><a id="dbcget_DB_PREV"></a>
<code class="literal">DB_PREV</code>
</p>
<p>
If the cursor is not yet initialized, DB_PREV is identical to DB_LAST.
Otherwise, the cursor is moved to the previous key/data pair of the
database, and that pair is returned. In the presence of duplicate key
values, the value of the key may not change.
</p>
<p>
If the database is a Queue or Recno database,
<code class="methodname">Dbc::get()</code> using the
DB_PREV flag will skip any keys that exist but
were never explicitly created by the application,
or those that were created and later deleted.
</p>
<p>
The <code class="methodname">Dbc::get()</code> method
will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if DB_PREV is set and the cursor is already on the
first record in the database.
</p>
</li>
<li>
<p><a id="dbcget_DB_PREV_DUP"></a>
<code class="literal">DB_PREV_DUP</code>
</p>
<p>
If the previous key/data pair of the database is a duplicate data
record for the current key/data pair, the cursor is moved to the
previous key/data pair of the database, and that pair is returned.
</p>
<p>
The <code class="methodname">Dbc::get()</code> method
will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if DB_PREV_DUP is set and the previous key/data
pair of the database is not a duplicate data
record for the current key/data pair.
</p>
<p>
If using a Heap database, this flag results in this
method returning
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>.
</p>
</li>
<li>
<p><a id="dbcget_DB_PREV_NODUP"></a>
<code class="literal">DB_PREV_NODUP</code>
</p>
<p>
If the cursor is not yet initialized,
DB_PREV_NODUP is identical to DB_LAST. Otherwise,
the cursor is moved to the previous non-duplicate
key of the database, and that key/data pair is
returned.
</p>
<p>
If the database is a Queue or Recno database,
<code class="methodname">Dbc::get()</code> using the
DB_PREV_NODUP flag will ignore any keys that exist
but were never explicitly created by the
application, or those that were created and later
deleted.
</p>
<p>
The <code class="methodname">Dbc::get()</code> method
will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if DB_PREV_NODUP is set and no non-duplicate
key/data pairs exist before the cursor position in
the database.
</p>
<p>
If using a Heap database, this flag is identical to
the <code class="literal">DB_PREV</code> flag.
</p>
</li>
<li>
<p><a id="dbcget_DB_SET"></a>
<code class="literal">DB_SET</code>
</p>
<p>
Move the cursor to the specified key/data pair of the database, and
return the datum associated with the given key.
</p>
<p>
The <code class="methodname">Dbc::get()</code> method will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if DB_SET is set and no matching keys are found.
The <code class="methodname">Dbc::get()</code> method
will return
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_KEYEMPTY" class="olink">DB_KEYEMPTY</a>
if DB_SET is set and the database is a Queue or
Recno database, and the specified key exists, but
was never explicitly created by the application or
was later deleted. In the presence of duplicate key
values, <code class="methodname">Dbc::get()</code> will
return the first data item for the given key.
</p>
</li>
<li>
<p><a id="dbcget_DB_SET_RANGE"></a>
<code class="literal">DB_SET_RANGE</code>
</p>
<p>
Move the cursor to the specified key/data pair of the
database. In the case of the Btree access method, the key
is returned as well as the data item and the returned
key/data pair is the smallest key greater than or equal to
the specified key (as determined by the Btree comparison
function), permitting partial key matches and range
searches.
</p>
<p>
In all other ways the behavior of this flag is the same
as the
<a class="link" href="dbcget.html#dbcget_DB_SET">DB_SET</a> flag.
</p>
</li>
<li>
<p><a id="dbcget_DB_SET_RECNO"></a>
<code class="literal">DB_SET_RECNO</code>
</p>
<p>
Move the cursor to the specific numbered record of
the database, and return the associated key/data
pair. The <span class="bold"><strong>data</strong></span>
field of the specified
<span class="bold"><strong>key</strong></span> must be a pointer
to a memory location from which a
<code class="literal">db_recno_t</code> may be read, as
described in
<a class="link" href="dbt.html" title="Chapter 4.  The Dbt Handle">Dbt</a>. This memory
location will be read to determine the record to
be retrieved.
</p>
<p>
For DB_SET_RECNO to be specified, the underlying database must be of
type Btree, and it must have been created with the
<a class="link" href="dbset_flags.html#dbset_flags_DB_RECNUM">DB_RECNUM</a>
flag.
</p>
</li>
</ul>
</div>
<p>
In addition, the following flags may be set by bitwise inclusively
<span class="bold"><strong>OR</strong></span>'ing them into the <span class="bold"><strong>flags</strong></span> parameter:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<code class="literal">DB_IGNORE_LEASE</code>
</p>
<p>
This flag is relevant only when using a replicated
environment.
</p>
<p>
Return the data item irrespective of the state of
master leases. The item will be returned under
all conditions: if master leases are not
configured, if the request is made to a client, if
the request is made to a master with a valid
lease, or if the request is made to a master
without a valid lease.
</p>
</li>
<li>
<p><a id="dbcget_DB_READ_COMMITTED"></a>
<code class="literal">DB_READ_COMMITTED</code>
</p>
<p>
Configure a transactional get operation to have degree 2 isolation
(the read is not repeatable).
</p>
</li>
<li>
<p>
<code class="literal">DB_READ_UNCOMMITTED</code>
</p>
<p>
Database items read during a transactional call will have degree 1
isolation, including modified but not yet committed data. Silently
ignored if the
<a class="link" href="dbopen.html#dbopen_DB_READ_UNCOMMITTED">DB_READ_UNCOMMITTED</a>
flag was not specified when the underlying database was opened.
</p>
</li>
<li>
<p><a id="dbcget_DB_MULTIPLE"></a>
<code class="literal">DB_MULTIPLE</code>
</p>
<p>
Return multiple data items in the <span class="bold"><strong>data</strong></span> parameter.
</p>
<p>
In the case of Btree or Hash databases, duplicate data items for the
current key, starting at the current cursor position, are entered into
the buffer. Subsequent calls with both the DB_NEXT_DUP and
DB_MULTIPLE flags specified will return additional duplicate data
items associated with the current key or
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a> if
there are no additional duplicate data items to return. Subsequent
calls with both the DB_NEXT and DB_MULTIPLE flags specified will
return additional duplicate data items associated with the current key
or if there are no additional duplicate data items will return the
next key and its data items or
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if there are no additional keys in the database.
</p>
<p>
In the case of Queue or Recno databases, data items starting at the
current cursor position are entered into the buffer. The record
number of the first record will be returned in the <span class="bold"><strong>key</strong></span> parameter. The record number of each
subsequent returned record must be calculated from this value.
Subsequent calls with the DB_MULTIPLE flag specified will return
additional data items or
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if there are no additional data items to return.
</p>
<p>
The buffer to which the <span class="bold"><strong>data</strong></span>
parameter refers must be provided from user memory (see
<a class="link" href="dbt.html#dbt_DB_DBT_USERMEM">DB_DBT_USERMEM</a> ).
The buffer must be at least as large as the page size of the
underlying database, aligned for unsigned integer access, and be a
multiple of 1024 bytes in size. If the buffer size is insufficient,
then upon return from the call the size field of the <span class="bold"><strong>data</strong></span> parameter will have been set to an
estimated buffer size, and the error DB_BUFFER_SMALL is returned.
(The size is an estimate as the exact size needed may not be known
until all entries are read. It is best to initially provide a
relatively large buffer, but applications should be prepared to resize
the buffer as necessary and repeatedly call the method.)
</p>
<p>
The multiple data items can be iterated over using the
<span>
<a class="xref" href="dbmultipledataiterator.html" title="DbMultipleDataIterator">DbMultipleDataIterator</a> class.
</span>
</p>
<p>
The DB_MULTIPLE flag may only be used with the DB_CURRENT, DB_FIRST,
DB_GET_BOTH, DB_GET_BOTH_RANGE, DB_NEXT, DB_NEXT_DUP, DB_NEXT_NODUP,
DB_SET, DB_SET_RANGE, and DB_SET_RECNO options. The DB_MULTIPLE flag
may not be used when accessing databases made into secondary indices
using the <a class="xref" href="dbassociate.html" title="Db::associate()">Db::associate()</a> method.
</p>
</li>
<li>
<p><a id="dbcget_DB_MULTIPLE_KEY"></a>
<code class="literal">DB_MULTIPLE_KEY</code>
</p>
<p>
Return multiple key and data pairs in the <span class="bold"><strong>data</strong></span> parameter.
</p>
<p>
Key and data pairs, starting at the current cursor position, are
entered into the buffer. Subsequent calls with both the DB_NEXT and
DB_MULTIPLE_KEY flags specified will return additional key and data
pairs or
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a>
if there are no additional key and data items to return.
</p>
<p>
In the case of Btree or Hash databases, the multiple key and data
pairs can be iterated over using the
<span>
<a class="xref" href="dbmultiplekeydataiterator.html" title="DbMultipleKeyDataIterator">DbMultipleKeyDataIterator</a> class.
</span>
</p>
<p>
In the case of Queue or Recno databases, the multiple record number
and data pairs can be iterated over using the
<span>
<a class="xref" href="dbmultiplerecnodataiterator.html" title="DbMultipleRecnoDataIterator">DbMultipleRecnoDataIterator</a> class.
</span>
</p>
<p>
The buffer to which the <span class="bold"><strong>data</strong></span>
parameter refers must be provided from user memory (see
<a class="link" href="dbt.html#dbt_DB_DBT_USERMEM">DB_DBT_USERMEM</a> ).
The buffer must be at least as large as the page size of the
underlying database, aligned for unsigned integer access, and be a
multiple of 1024 bytes in size. If the buffer size is insufficient,
then upon return from the call the size field of the <span class="bold"><strong>data</strong></span> parameter will have been set to an
estimated buffer size, and the error DB_BUFFER_SMALL is returned.
(The size is an estimate as the exact size needed may not be known
until all entries are read. It is best to initially provide a
relatively large buffer, but applications should be prepared to resize
the buffer as necessary and repeatedly call the method.)
</p>
<p>
The DB_MULTIPLE_KEY flag may only be used with the DB_CURRENT,
DB_FIRST, DB_GET_BOTH, DB_GET_BOTH_RANGE, DB_NEXT, DB_NEXT_DUP,
DB_NEXT_NODUP, DB_SET, DB_SET_RANGE, and DB_SET_RECNO options. The
DB_MULTIPLE_KEY flag may not be used when accessing databases made
into secondary indices using the
<a class="xref" href="dbassociate.html" title="Db::associate()">Db::associate()</a> method.
</p>
</li>
<li>
<p><a id="dbcget_DB_RMW"></a>
<code class="literal">DB_RMW</code>
</p>
<p>
Acquire write locks instead of read locks when doing the read, if
locking is configured. Setting this flag can eliminate deadlock
during a read-modify-write cycle by acquiring the write lock during
the read part of the cycle so that another thread of control acquiring
a read lock for the same item, in its own read-modify-write cycle,
will not result in deadlock.
</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h3 class="title"><a id="id3587399"></a>Errors</h3>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
The <code class="methodname">Dbc::get()</code> <span>
<span>
method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
exception, encapsulating one of the following non-zero errors, or return one
of the following non-zero errors:
</span>
</span>
</p>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3587536"></a><span>DbMemoryException or </span>DB_BUFFER_SMALL</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
The requested item could not be returned due to undersized buffer.
</p>
<p>
<a class="xref" href="dbmemory.html" title="DbMemoryException">DbMemoryException</a> is thrown if
your Berkeley DB API is configured to throw exceptions.
Otherwise, <code class="literal">DB_BUFFER_SMALL</code> is returned.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3587182"></a><span>DbDeadlockException or </span>DB_LOCK_DEADLOCK</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
A transactional database environment operation was selected to resolve
a deadlock.
</p>
<p>
<a class="xref" href="dbdeadlock.html" title="DbDeadlockException">DbDeadlockException</a> is thrown if
your Berkeley DB API is configured to throw exceptions.
Otherwise, <code class="literal">DB_LOCK_DEADLOCK</code> is returned.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3586009"></a><span>DbLockNotGrantedException or </span>DB_LOCK_NOTGRANTED</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
A Berkeley DB Concurrent Data Store database environment configured
for lock timeouts was unable to grant a lock in the allowed time.
</p>
<p>
<a class="xref" href="dblocknotgranted.html" title="DbLockNotGrantedException">DbLockNotGrantedException</a> is thrown if
your Berkeley DB API is configured to throw exceptions.
Otherwise, <code class="literal">DB_LOCK_NOTGRANTED</code> is returned.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3585416"></a> <span>DbRepHandleDeadException or</span> DB_REP_HANDLE_DEAD</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
When a client synchronizes with the master, it is possible for committed
transactions to be rolled back. This invalidates all the database and cursor
handles opened in the replication environment. Once this occurs, an attempt to use
such a handle will
<span>
throw a <a class="xref" href="dbrephandledead.html" title="DbRepHandleDeadException">DbRepHandleDeadException</a> (if
your application is configured to throw exceptions), or
</span>
return <code class="literal">DB_REP_HANDLE_DEAD</code>.
The application will need to discard the handle and open a new one in order to
continue processing.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3585961"></a>DB_REP_LEASE_EXPIRED</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
The operation failed because the site's replication master lease has expired.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3586346"></a><span>DbDeadlockException or </span>DB_REP_LOCKOUT</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
The operation was blocked by client/master synchronization.
</p>
<p>
<a class="xref" href="dbdeadlock.html" title="DbDeadlockException">DbDeadlockException</a> is thrown if
your Berkeley DB API is configured to throw exceptions.
Otherwise, <code class="literal">DB_REP_LOCKOUT</code> is returned.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3585397"></a>DB_SECONDARY_BAD</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
A secondary index references a nonexistent primary key.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h4 class="title"><a id="id3586036"></a>EINVAL</h4>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
If the DB_CURRENT, DB_NEXT_DUP or DB_PREV_DUP flags were
specified and the cursor has not been initialized; the
<code class="methodname">Dbc::pget()</code> method was called with
a cursor that does not refer to a secondary index; or if an
invalid flag value or parameter was specified.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h3 class="title"><a id="id3587509"></a>Class</h3>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
<a class="link" href="dbc.html" title="Chapter 3.  The Dbc Handle">Dbc</a>
</p>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
Release 5.2.36 on 9/14/2022
2011-12-20 00:07:10 +00:00
<h3 class="title"><a id="id3586042"></a>See Also</h3>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
</div>
</div>
<p>
<a class="xref" href="dbc.html#dbclist" title="Database Cursors and Related Methods">Database Cursors and Related Methods</a>
</p>
</div>
</div>
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