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<h2 class="title" style="clear: both"><a id="stl_container_specific"></a>Dbstl container specific notes</h2>
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<dt>
<span class="sect2">
<a href="stl_container_specific.html#idp51492808">db_vector specific notes</a>
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<span class="sect2">
<a href="stl_container_specific.html#idp51561456">Associative container specific notes</a>
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<h3 class="title"><a id="idp51492808"></a>db_vector specific notes</h3>
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<ul type="disc">
<li>
<p>
Set the <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> flag in the database handle if you want
<code class="classname">db_vector<></code> to work like
<code class="classname">std::vector</code> or <code class="classname">std::deque</code>. Do not set
<a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> if you want <code class="classname">db_vector<></code> to work like
<code class="classname">std::list</code>. Note that without <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> set,
<code class="classname">db_vector<></code> can work faster.
</p>
<p>
For example, to construct a fast std::queue/std::stack object, you only need a
<code class="classname">db_vector<></code> object whose database handle does not have
<a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> set. Of course, if the database handle has <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> set, it
still works for this kind of scenario, just not as fast.
</p>
<p>
<code class="classname">db_vector</code> does not check whether <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> is set. If
you do not set it, <code class="classname">db_vector<></code> will not work like
std::vector<>/std::deque<> with regard to operator[], because the
indices are not maintained in that case.
</p>
<p>
You can find example code showing how to use this feature in the
<code class="methodname">StlAdvancedFeaturesExample::queue_stack()</code> method.
</p>
</li>
<li>
<p>
Just as is the case with <code class="classname">std::vector</code>, inserting/deleting in
the middle of a <code class="classname">db_vector</code> is slower than doing the same
action at the end of the sequence. This is because the underlying DB_RECNO DB (with
the <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> flag set) is relatively slow when inserting/deleting in the middle
or the head — it has to update the index numbers of all the records following
the one that was inserted/deleted. If you do not need to keep the index ordered on
insert/delete, you can use <code class="classname">db_map</code> instead.
</p>
<p>
<code class="classname">db_vector</code> also contains methods inherited from
<code class="classname">std::list</code> and <code class="classname">std::deque</code>,
including <code class="classname">std::list<>'s</code> unique methods
<code class="methodname">remove()</code>, <code class="methodname">remove_if()</code>,
<code class="methodname">unique()</code>, <code class="methodname">merge()</code>,
<code class="methodname">sort()</code>, <code class="methodname">reverse()</code>, and
<code class="methodname">splice()</code>. These use the identical semantics/behaviors
of the <code class="classname">std::list<></code> methods, although
pushing/deleting at the head is slower than the
<code class="methodname">std::deque</code> and <code class="methodname">std::list</code>
equivalent when there are quite a lot of elements in the database.
</p>
</li>
<li>
<p>
You can use <code class="classname">std::queue</code>,
<code class="classname">std::priority_queue</code> and <code class="classname">std::stack</code>
container adapters with <code class="classname">db_vector</code>; they work with db_vector
even without <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_RENUMBER" class="olink">DB_RENUMBER</a> set.
</p>
</li>
</ul>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp51561456"></a>Associative container specific notes</h3>
</div>
</div>
</div>
<p>
<code class="classname">db_map</code> contains the union of method set from
<code class="classname">std::map</code> and <code class="classname">hash_map</code>, but there are some
methods that can only be called on containers backed by <code class="literal">DB_BTREE</code> or
<code class="literal">DB_HASH</code> databases. You can call
<code class="function">db_map<>::is_hash()</code> to figure out the type of the backing
database. If you call unsupported methods then an InvalidFunctionCall exception is thrown.
</p>
<p>
These are the <code class="literal">DB_BTREE</code> specific methods: <code class="methodname">upper_bound()</code>,
<code class="methodname">lower_bound()</code>, <code class="methodname">key_comp()</code>,
and <code class="methodname">value_comp()</code>. The <code class="literal">DB_HASH</code> specific methods are
<code class="methodname">key_eq()</code>, <code class="methodname">hash_funct()</code>.
</p>
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