DataViewer

The DataViewer turns a MySQL table into a searchable, sortable spreadsheet on a hub page. It has no content of its own and no list of things to manage: it is a renderer that other components link into, and every table it draws belongs to something else. On a hub built from this repository the only thing that links into it is the Projects - Databases plugin, whose DataStore Lite databases open in the DataViewer, and the publications that attach one.

There is an administrator screen at Components → DataViewer, but it edits configuration files belonging to a separate com_databases component that is not part of Hubzero 2.4. On a stock hub that screen lists nothing and there is nothing on it to do. What the DataViewer actually needs from you is set elsewhere: the read-only MySQL account on the Projects - Databases plugin. Without it the DataViewer cannot read anything, and the Databases tab does not appear in projects at all.

So the question this chapter answers is narrow. A project team asks to keep a few thousand rows of measurements on the hub and have people browse them rather than download a spreadsheet. That is what the DataViewer is for, and what it costs you is two MySQL accounts and one plugin. A hub whose projects only ever exchange files needs none of it, and can stop reading here.

What it is not

The DataViewer is not a database manager, and it is not somewhere you put data. It never creates a table, has no import screen, and holds no rows of its own; a project team creates the data through the project's own Databases tab. It is also not a chart tool for arbitrary content — it draws exactly the tables another component hands it, and on this hub that means project databases and the publications built from them.

What a manager has to configure

Do this once, before the first project team asks. Both accounts go on one plugin, and getting the read-only one wrong is the fault you will spend an afternoon on, because the symptom appears in a project rather than here.

Everything that makes the DataViewer work is on the Projects - Databases plugin, not on this component:

1. Go to Extensions → Plug-in Manager and open Projects - Databases.
2. Set Database Host, the read/write account (Database User [rw], Database Password [rw]) that creates the tables, and the read-only account (Database User [ro], Database Password [ro]) that the DataViewer reads them with. The read-only user defaults to dataviewer.
3. Set Status to Enabled and select Save & Close.

See Projects for the rest of that plugin, and Databases in the users book for what a project team does with the result.

Where the DataViewer appears

Nothing on the hub links to /dataviewer on its own. Two things link into it:

Link comes from	URL it builds
A project's Databases tab	/dataviewer/view/<project alias>:dsl/<database name>/
A data attachment on a publication	/dataviewer/view/publication:dsl/<database name>/?v=<version>

The segment after the colon is the mode. Three modes exist in the code:

Mode	Reads from	State in Hubzero 2.4
dsl	#__project_databases, using the Projects - Databases plugin's read-only account	Works. This is the one the hub uses.
db	JSON configuration files under a com_databases base directory	Inert — com_databases does not ship with the CMS
ds	A com_datastores component's ds_* databases	Inert — com_datastores does not ship with the CMS

A hub that has none of the extra components installed only ever sees dsl.

Who can see a data view

Access is decided per data view, not per hub. In dsl mode:

• An unpublished project database is visible to the project's owners.
• A database attached to a published publication version is public.
• A database attached to an unpublished version is visible to the project's owners and to the publication's curator and curator groups.
• A visitor who is not logged in and is not entitled to see the data is sent to the login form.

The component's own ACL Users and ACL Groups options are a second, blunter layer. ACL Users never takes effect on a project database, because the data view supplies its own user list and that list wins. ACL Groups does take effect, because a project database supplies no group list.

What a visitor sees

The data view opens as a table with a global search box, per-column filters, and a page-size selector. Above it is a toolbar; which buttons appear depends on what the data definition declares:

Button	What it does	When it appears
Download	Downloads the current result set as CSV	Unless the data definition turns it off
Fullscreen	Expands the table to the whole window	Unless the data definition turns it off
Filter Dialog	Opens the data definition's own filter form	When the data definition declares filters
Clear Filters	Clears the column filters and the global search	Always
No-Wrap	Stops cell text wrapping	Unless the data definition turns it off
Charts	Opens a chart panel, with Download Chart	When the data definition declares charts
Maps	Opens a map panel, with KML, KMZ and SHP exports	When the data definition declares show_maps
Customize DataView	Lets the reader pick a subset of columns	When the data definition declares a customizer

Large tables switch from browser-side to server-side processing on their own when Dynamic Processing mode is on; see the options below.

The administrator screen

Components → DataViewer opens a screen headed Database List. It scans a base directory on disk — taken from com_databases, or /db/databases when that component is absent — for */database.json files, and lists one row per database it finds, with links to Edit Config and Dataviews. Those lead to a pair of JSON editors: one for a per-database DataViewer configuration file, one for individual data definitions.

On a hub installed from this repository the directory does not exist, so the list is empty and there is nothing to open. The only working control on the screen is Options.

Project databases do not appear here. Their data definitions live in the #__project_databases table and are built by the project team through the Databases tab, not by editing files.

Options

Select Options on the DataViewer screen. The full parameter list is in the generated reference.

• Record Display Limit — rows per page in a new data view: 5, 10, 25, 50 or 100.
• Dynamic Processing mode and Client-side threshold — when the mode is on, a data view whose row count times its visible column count exceeds the threshold is paged and sorted by the database instead of in the browser. Raising the threshold makes small tables feel faster and large ones slower; lowering it does the reverse. The threshold is counted in cells, not rows.
• DB Mode enabled — only meaningful with the separate com_databases component installed. Leave it off.
• ACL Users and ACL Groups — see the warning above.

The Permissions tab has no effect at all: nothing in the component reads the actions it sets. Access to a data view is decided per data view, and access to the administrator screen is not decided at all.

What does not work

• The db and ds modes. Both need components that are not part of Hubzero 2.4. A URL that names either mode fails.
• File and image columns. A data definition that declares a file or gallery column renders links to /dataviewer/file/… and /dataviewer/gallery/…. The component implements only two front-end tasks, view and data, so both links return Invalid or Missing Dataview. The view templates that would serve them are present but unreachable. Only the DataStores mode produced such columns, so a project database is unaffected.
• The Maps panel. It loads the Google Maps JavaScript API with no API key and with the long-removed sensor parameter. Google refuses unkeyed requests, so the map does not draw. The KML, KMZ and SHP export buttons in the same panel are generated server-side and do work — but they are inside the panel the map failed to fill.

The component's own database access

The DataViewer connects to the data with mysqli directly, using the credentials it is handed for the mode, and not through the CMS's database layer. That is why the read-only account on the Projects - Databases plugin matters and why a mistake in it produces a raw connection error on the page rather than a Hubzero error message.