DKAN Data Preview Features¶
DKAN allows users to have a preview of their data when uploaded to or linked to a resource. Which preview type is displayed for a particular resource depends on the data format selected. If no data format is provided, DKAN will attempt to auto-detect the format from the file’s metadata; re-editing the resource and correcting the format field manually may be necessary if the auto-detection is not successful.
This functionality is provided via the Recline module, which is not part of the core DKAN repository but is a basic dependency of it (and will be included when building the distribution via
Record limit: The previews will display up to 100 records by default. You can use the pager to preview additional results based on the range given. If you want to preview more than 100 records at a time, adjust the max range value to the desired range.
All tabular data can be rendered as spreadsheet-style rows and columns:
|[*]||For xls files be sure to fill in the format field to see previews of the data|
Visitors can preview data that contains either coordinates or GeoJSON on a Leaflet.js -based map:
If enabled, visitors can chose one column of your data as an X-axis, one or more as Y-axis data, and preview your data as a bar, point or line graph.
File size limits¶
Files can only be previewed if they are well formatted and small enough to render in the browser.
If files are too large to preview within 1 second you will get the following message “File was too large or unavailable for preview.”
Files that are too large to preview in the browser can be previewed by adding them to the datastore. Once a file is in the datastore the preview is only asking for the first 25 rows of the data. Thus large datasets can be previewed.
Additional Preview Types¶
DKAN provides preview formats for several additional file types beyond what is supported by Recline.js, these include: JSON, geojson, XML, ArcGIS REST, WMS, images, PDF, and ZIP files. These additional preview formatters are defined in a forked version of Recline
DKAN offers the ability to preview the files and folders locked in ZIP files. DKAN will display a list of contents for ZIP files uploaded as resources on datasets.
Image files (JPG, PNG or GIF) uploaded as resources will be displayed directly on the resource page.
Web Map Service (WMS)¶
DKAN can use Leaflet to display a preview of a WMS server, provided endpoint.
WMS support in DKAN is still somewhat experimental and your results may vary.
An ESRI/ArcGIS REST endpoint may also be displayed in a Leaflet preview.
Starting with version 7.x-1.10, DKAN supports previewing/opening resources in external services that offer simple URL-based integrations. For instance, the CartoDB mapping service offers an Open in CartoDB service. Enabling this for CSV files will result in a dataset display like this:
External preview functionality can be enabled and configured in the “DKAN Dataset Previews” administration page (/admin/dkan/dataset_preview).
By default previews are available for resources with files below 3MB of size. However you can customize this limit in the recline configuration page (/admin/dkan/recline).