Loading data efficiently

Many pages use components (web parts or controls) to load and display data from the Kentico database, or other external sources. Transferring data between storage spaces and the application can be a performance bottleneck.

To maximize data loading efficiency, consider the following points when setting up data source components.

Only load the data columns that you need

When loading data, you usually do not need all columns available in the source. The less data you retrieve, the faster your pages will be.

You can limit which columns data sources load through the Columns (or Selected columns) property. Enter a list of column names separated by commas. We recommend loading only the columns that your components need to display the required results:

  • Columns used in the code of transformations
  • Columns inside Where conditions, Order by clauses etc.

When loading Kentico documents, the behavior of the Columns property depends on the type of the data source:


Standard document data sources load all columns if you leave the Columns property empty. The full list includes the columns of the View_CMS_Tree_Joined database view, and the coupled data columns of individual document types.

By setting the Columns property, you specify exactly which of the columns the data source retrieves.

Note: In addition to the columns that you specify in the Columns property, the data source always loads a set of specific columns that allow the system to identify individual documents (NodeID, DocumentCulture, etc.).


Data sources of navigation components always load a set of default columns required to correctly display documents in menus.

The Columns property only allows you to add extra columns. Leave the property empty unless your component requires a field that is not included in the defaults.

Note: To find a full list of the default navigation columns, use the SQL queries debugging tool and inspect the query performed by your navigation component.

To learn how Kentico stores documents in the database, refer to Document database structure.


Disable unnecessary processing

Document data sources provide features for filtering data according to the settings and status of the website's documents. All such operations add steps to the data retrieval process and use the system's resources. By disabling filtering options that you do not need, you can reduce processing overhead when loading uncached data.

Consider the following when configuring the properties of document data sources:

  • If you are not loading sensitive data (secured documents), disable the data source's Check permissions property.
  • If the website's documents do not use workflow or content scheduling (i.e. documents are always published immediately), disable the Select only published property.

Disable view state for web parts

By default, web parts store data in the page's view state. If view state contains a large amount of information, it can slow down page performance.

You can turn off view state for web parts that do not need to preserve their state across postbacks:

  1. Open the Pages application.
  2. Select the page containing the web part.
  3. On the Design tab, configure the given web part instance (double-click).
  4. Enable the Disable view state property in the Performance category.

Disabling view state reduces processing overhead and the size of the page output that clients need to download. As a result, page load time improves (depending on the size of the view state).

Note: Test your web parts carefully after disabling view state. Web parts may not work correctly without view state in some scenarios.

Example - Optimizing a news list

The following example demonstrates how to maximize the performance of a Repeater web part. Repeaters load data from documents in the website's content tree, and use transformations to format the data into HTML output.

In this sample scenario, the Repeater displays news documents with the following configuration and environment:

  • The website does not use workflow, all documents are published.
  • All of the website's documents are publicly available without security requirements.
  • The Repeater web part:
    • loads CMS.News documents as the data
    • uses an ORDER BY expression: NewsReleaseDate DESC
    • renders the data using the following Text type transformations:

    List item transformation  Expand source
    <div class="listBoxWithTeaser">
    	<div class="teaser">
    		{% GetImage(NewsTeaser, "", 90) %}
     	<div class="description">
    		<a class="header bold" href="{% GetDocumentUrl() %}">
    			{% HTMLEncode(NewsTitle) %}
    			<span class="black bold">
    				By {% GetUserFullName(NodeOwner) %}
    			</span><br /><br />
    			{% NewsSummary %}
    Item detail transformation  Expand source
    <div class="listDetail">
    		{% HTMLEncode(NewsTitle) %}
    	<div class="teaser">
    		{% GetImage(NewsTeaser, "", 230, 230, 500) %}
    	<div class="contentText contentTextTeaser">
    		<div class="summary">
    			<p>{% NewsSummary %}</p>
    		<div class="text">
    			<p>{% NewsText %}</p>

To optimize how the Repeater loads data, perform the following steps:

  1. Open the Pages application.
  2. Configure the Repeater web part on the Design tab.
  3. Set the following Columns (in the Content filter category):
    NewsReleaseDate, NewsTeaser, NewsTitle, NewsSummary, NewsText, NodeOwner, NodeAlias, DocumentURLPath, NodeAliasPath

    • Column used in the ORDER BY expression
    • Columns accessed directly inside the transformations
    • Column required by the GetImage method in the transformations
    • Columns required by the GetDocumentUrl() transformation method

  4. Disable Select only published (Content filter category).
  5. Disable Check permissions (System settings category).
  6. Check the Disable view state property (Performance category).
  7. Configure caching for the web part:
  8. Click OK.

The web part now loads only the required data columns, skips unnecessary processing, and uses caching. This Repeater does not use filtering or paging, so it is safe to disable view state.