Other parameters: Difference between revisions

The <code>updaterules</code> feature is intended for wiki expert users only. It is recommended that articles usindusing this statement are 'protected':

The regexp will implicitly be enclosed in slashes. Hence, literal slash characters must be escaped by backslashes.

The regexp will implicitly be enclosed in slashes. Hence, literal slash characters must be escaped by backslashes.

The regexp will implicitly be enclosed in slashes. Hence, literal slash characters must be escaped by backslashes.

For safety reasons, the update statements will only be performed if "exec yes" is specified. So, leaving this away, you can check what would happen if the update were to be executed.

Note that if "exec yes" is present, the update will be performed each time the page is rendered which contains the DPL statement with the <code>updaterules</code>. So it is advisable to set "exec yes" only via a command line argument and not as part of the statiocstatic article text. Thus, you stay in control when the update happens. Typically, one would use ana URL parameter like ''DPL_arg1'' for that purpose.

<!--To make the use of the <code>updaterules</code> feature easier, we provide a [[Template:Bulk Update|special user interface]].

Note: This template is deliberately not present, as it can apparently alter lots of wiki content. The line above is retained as a comment, since it was part of the original DPL documentation. -->

Default is 'pages', which means that DPL produces a list of pages. And this is exactlyprecisely what the name DPL promises.

If you set the goal parameter to 'categories' the list of pages will still be produced, but you won't see it. Instead, it will be used to '''calculate a unique ordered list of all categories these pages belong to'''.

This allows you to ask a question like: Given all pages that are a member of category X with a title matching "y%" and which use template "Z": to which categories do these pages belong?

One of the more useful applications would be a question like: "To which categories do the pages belong which contain a reference to the current page?"

Due to some limitations in MySQL, it is currently not possible to restrict the intermediate result set of pages to a certain maximum (using the LIMIT clause). In addition, the generated SQL code is not in all cases optimal (as its structure provides for complex selection criteria and therefore is unnecessarily complex in simple cases). So be careful and apply precise selection criteria.

|purpose= Cache query results to improve performance, keep servers from crashing under high load.

All queries are cached by default to reduce server load, as generally articles do not change often enough to require updating every page load. If immediate updates are required every page load, then set this parameter to false. The cache period is handled by the [[#cacheperiod]] parameter.

In some cases, this may be useful. But in many cases, this is not wanted. Especially when you use DPL to create a printable document which contains the full text of other articles, you will probably not want to duplicate all links, template uses etc. of those articles.

There are some subtle differences here depending on the mode in which you use DPL. These differences affect the question of how links, and categories etc., are treated which are direct part of the document containing the DPL query.

;reset=links: will throw away all references to other pages, i.e., links contained in included contents and links like 'Q Link' will be ignored. This means that all links can be used in the normal "FORWARD" way, but no "BACKLINKS" are available for them.

If you want to avoid the above described effect of <code>reset</code> on your 'own' links, you can use {{dpl3|eliminate}}. But you should know that ''eliminate'' is rather expensive in terms of computer power, as it does a second parse for all included contents.

As you see, using <code>reset</code> in parser function mode will clear everything, regardless whether it comes from included contents or whether it is direct part of the document containing the DPL query.

If you want to avoid the above described effect of <code>reset</code>, you can use {{dpl3|eliminate}}</code>. But you should know that ''eliminate'' is rather expensive in terms of computing power, as it does a second parse for all included contents. The extra parser step is conducted as soon as you specify <code>eliminate</code>. In terms of extra processing needed, it does not make a difference whether you specify one or more arguments for the 'eliminate' command.

If you have '''more than one DPL query''' in a document the effects will depend on the exact mode (parser extension or parser function mode), on the sequence of the statements and on the presence of 'reset' or 'eliminate' statements in each of the queries and on their individual arguments. As this is a very rare case, we only give a simple rule of thumb here: Once you have used 'reset' in parser function mode or 'reset=links' in parser extension mode, the effect of these statements will dominate the rest.

|purpose= assign the article containing a DPL statement to a category, although <code>reset</code> was used.

If you use <code>reset=all</code> or <code>reset=categories</code> the article containing your DPL statement will not be recorded in the mediawiki link database. This may be quite useful if your article transcludes content from other pages. Without the <code>reset</code> command, your article would appear in a category if you included a text portion containing an assignment to that category.

In some cases, this may be useful. But in many cases, this is not wanted. Especially when you use DPL to create a printable document which contains the full text of other articles, you will probably not want to duplicate all links, template uses etc., of those articles.

For further explanation, see {{dpl3|reset}}.

This list will output the error for the first namespace: ''Media'' is not a valid [[#namespace|namespace]] value (pseudo-namespace). Assuming you haven't changed the default debug value (2), you will also get a warning: <code>debug=1</code> is not input first (before <code>namespace=Media</code>). So, it did not apply to <code>namespace=Media</code> but only to what's after. Indeed, you won't get the warning for the second namespace (''Special'') since <code>debug=0</code> changed debug settings to silent mode.

'debug=1' will suppress warning messages (e.g., if the result set of a DPL query is empty). As an alternative, you can use the {{dpl3|suppresserrors}} statement.

If no wiki text is given, the command will be ignored. Otherwise, DPL will output the wiki text and exit immediately.

The special word ''geturlargs'' can be used as a wiki text to transform URL arguments starting with <code>DPL_</code> into variables, which can then be accessed via #var (if the Variables extension is installed) or via #dplvar.

Using this command, you can prevent DPL from executing a database query; this may be useful if a necessary parameter was not given by the user. Note that an ''#if'' function call would NOT help in that case because ''#if'' evaluates its complete content before taking the "if" or the "else" path. So, emebdding a DPL call within a #if is much less efficient than using the ''execandexit'' function.