Current File : //home/bitrix/www/bitrix/modules/main/lang/en/admin/checklist/QC0050.html
<p>When implementing cache support in custom components, the following rules
should be observed by a developer.</p>
<ol>
<li>In cached mode, a component must not perform database API calls or request
data from database in any other way. Unfortunately, a developer may
unwillingly make coding mistakes which allow database API calls to bleed
through even in cached mode.</li>
<li>When a component cannot find cached data for requested parameters, it has to
create such data and put it to the cache. When creating new data, the
component's database API calls must be painstakingly optimized. Sometimes
coding errors may cause excessive database load performing enormous amount of
SQL queries. </li>
</ol>
<p>It is recommended that you carefully analyze all database queries a component
performs and optimize the code by using filters, proper sort modes and reducing the
number of properties to fetch. </p>
<p>To analyze the SQL queries, the EXPLAIN command will come in handy for you.
Make sure your SQL selections use database indexes. This can be of great
importance for Components 2.0 because they can create indexes for columns of the
information block element properties table.</p>
<p>This approach should also be applied to database API calls in the service and
initialization scripts. Even if an optimized component is robust, fast and uses
caching, it may interact with an initialization script that executes an outburst
of numerous SQL queries which will kill all your optimization efforts.</p>
<p>To streamline your database optimization work, create and use an <i>optimization
status table</i>:</p>
<ul>
<li>Column 1: Web page address.</li>
<li>Column 2: SQL query count, cache disabled.</li>
<li>Column 3: SQL query count, cache enabled.</li>
<li>Column 4: SQL queries optimized. <i>(using the approach described above)</i></li>
</ul>
<p>Check all the website pages and fill the table with performance data. Your
aim is to get the numbers in (3) as small as possible (zero SQL queries is the
ideal value; the Web Analytics module, if used, may produce some surplus which
is normal); the number of SQL queries in (2) must be reduced to a bare minimum.
Once you have optimized a page, make a note in column (4). </p>
<p>You can use this table for your custom components if you like.</p>
<ol>
<li>Create and populate an optimization status table. If time presses, measure
performance of the most visited pages only. Minimize database load by
optimizing and adding cache functionality to unacceptably aggressive
components.</li>
<li>Ensure that all the service and initialization scripts are also optimized
and that they use only the Bitrix Framework API calls to execute database
queries. Direct database queries are not allowed.</li>
</ol>
Mini Shell