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</div><hr /><div id="mysqlinfo.concepts.buffering" class="section">
<h2 class="title">Buffered and Unbuffered queries</h2>
<p class="para">
Queries are using the buffered mode by default. This means that query results are
immediately transferred from the MySQL Server to PHP in is then kept in the memory
of the PHP process. This allows additional operations like counting the
number of rows, and moving (seeking) the current result pointer. It also allows
issuing further queries on the same connection while working on the result set.
The downside of the buffered mode is that larger result sets might require
quite a lot memory. The memory will be kept occupied till all references to the
result set are unset or the result set was explicitly freed, which will automatically
happen during request end the latest. The terminology "store result" is also used
for buffered mode, as the whole result set is stored at once.
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
When using libmysqlclient as library PHP's memory limit won't count the memory used
for result sets unless the data is fetched into PHP variables. With mysqlnd
the memory accounted for will include the full result set.
</p>
</p></blockquote>
<p class="para">
Unbuffered MySQL queries execute the query and then return a <span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span> while
the data is still waiting on the MySQL server for being fetched. This uses less memory
on the PHP-side, but can increase the load on the server. Unless the full result set was
fetched from the server no further queries can be sent over the same connection. Unbuffered
queries can also be referred to as "use result".
</p>
<p class="para">
Following these characteristics buffered queries should be used in cases where you expect
only a limited result set or need to know the amount of returned rows before reading all
rows. Unbuffered mode should be used when you expect larger results.
</p>
<p class="para">
Because buffered queries are the default, the examples below will demonstrate how to
execute unbuffered queries with each API.
</p>
<div class="example" id="example-1556">
<p><strong>Example #1 Unbuffered query example: mysqli</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$mysqli </span><span style="color: #007700">= new </span><span style="color: #0000BB">mysqli</span><span style="color: #007700">(</span><span style="color: #DD0000">"localhost"</span><span style="color: #007700">, </span><span style="color: #DD0000">"my_user"</span><span style="color: #007700">, </span><span style="color: #DD0000">"my_password"</span><span style="color: #007700">, </span><span style="color: #DD0000">"world"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$uresult </span><span style="color: #007700">= </span><span style="color: #0000BB">$mysqli</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT Name FROM City"</span><span style="color: #007700">, </span><span style="color: #0000BB">MYSQLI_USE_RESULT</span><span style="color: #007700">);<br /><br />if (</span><span style="color: #0000BB">$uresult</span><span style="color: #007700">) {<br /> while (</span><span style="color: #0000BB">$row </span><span style="color: #007700">= </span><span style="color: #0000BB">$uresult</span><span style="color: #007700">-></span><span style="color: #0000BB">fetch_assoc</span><span style="color: #007700">()) {<br /> echo </span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #DD0000">'Name'</span><span style="color: #007700">] . </span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br /> }<br />}<br /></span><span style="color: #0000BB">$uresult</span><span style="color: #007700">-></span><span style="color: #0000BB">close</span><span style="color: #007700">();<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<div class="example" id="example-1557">
<p><strong>Example #2 Unbuffered query example: pdo_mysql</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$pdo </span><span style="color: #007700">= new </span><span style="color: #0000BB">PDO</span><span style="color: #007700">(</span><span style="color: #DD0000">"mysql:host=localhost;dbname=world"</span><span style="color: #007700">, </span><span style="color: #DD0000">'my_user'</span><span style="color: #007700">, </span><span style="color: #DD0000">'my_pass'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$pdo</span><span style="color: #007700">-></span><span style="color: #0000BB">setAttribute</span><span style="color: #007700">(</span><span style="color: #0000BB">PDO</span><span style="color: #007700">::</span><span style="color: #0000BB">MYSQL_ATTR_USE_BUFFERED_QUERY</span><span style="color: #007700">, </span><span style="color: #0000BB">false</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$uresult </span><span style="color: #007700">= </span><span style="color: #0000BB">$pdo</span><span style="color: #007700">-></span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT Name FROM City"</span><span style="color: #007700">);<br />if (</span><span style="color: #0000BB">$uresult</span><span style="color: #007700">) {<br /> while (</span><span style="color: #0000BB">$row </span><span style="color: #007700">= </span><span style="color: #0000BB">$uresult</span><span style="color: #007700">-></span><span style="color: #0000BB">fetch</span><span style="color: #007700">(</span><span style="color: #0000BB">PDO</span><span style="color: #007700">::</span><span style="color: #0000BB">FETCH_ASSOC</span><span style="color: #007700">)) {<br /> echo </span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #DD0000">'Name'</span><span style="color: #007700">] . </span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br /> }<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<div class="example" id="example-1558">
<p><strong>Example #3 Unbuffered query example: mysql</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br />$conn </span><span style="color: #007700">= </span><span style="color: #0000BB">mysql_connect</span><span style="color: #007700">(</span><span style="color: #DD0000">"localhost"</span><span style="color: #007700">, </span><span style="color: #DD0000">"my_user"</span><span style="color: #007700">, </span><span style="color: #DD0000">"my_pass"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$db </span><span style="color: #007700">= </span><span style="color: #0000BB">mysql_select_db</span><span style="color: #007700">(</span><span style="color: #DD0000">"world"</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$uresult </span><span style="color: #007700">= </span><span style="color: #0000BB">mysql_unbuffered_query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT Name FROM City"</span><span style="color: #007700">);<br />if (</span><span style="color: #0000BB">$uresult</span><span style="color: #007700">) {<br /> while (</span><span style="color: #0000BB">$row </span><span style="color: #007700">= </span><span style="color: #0000BB">mysql_fetch_assoc</span><span style="color: #007700">(</span><span style="color: #0000BB">$uresult</span><span style="color: #007700">)) {<br /> echo </span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #DD0000">'Name'</span><span style="color: #007700">] . </span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br /> }<br />}<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
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