DPL:Manual - DPL parameters: Other parameters

From FollowTheScore
Revision as of 18:57, 12 June 2009 by Gero (talk | contribs)
Jump to: navigation, search
Manual Other parameters

updaterules

updaterules define a set of rules which are executed to perform an update on selected articles (bulk update)

Syntax: 

updaterules=
    rule;
    ...
    rule;

Where rule is one of the following: 

 before  pattern;
 after   pattern;
 insert  text;
 replace pattern;
 by      replacement;
 summary edit summary text;
 exec    true;

A pattern is a regular expression, typically enclosed within slashes; text is plain text; replacement is text which may contain references (like \1) to the matching pattern (provided that this pattern contains match groups).

The updaterules feature is intended for wiki expert users only. Wrongly used it can create a big mess in your wiki!

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

Note that if "exec true" is present the update will be performed each time the page is shown which contains the DPL statement with the updaterules. So it is advisable to remove "exec true" immediately after the page has been shown once.

To make the use of the updaterules feature easier we provide a special user interface.


deleterules

deleterules allow the mass deletion of wiki pages

deleterules= 

    reason text;
    exec true;

This will delete the selected pages; If "exec true" is missing, nothing will happen.


goal

goal set the overall goal for DPL to either show pages (default) or categories these pages belong to

Syntax:

goal=pages | categories

Explanation:

Default is 'pages', which means that DPL produces a list of pages. And this is exactly 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 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 question like: "To which categories do the pages belong which contain a reference to the current page?"

The output of "goal=categories" is technically a list of pages of type category. This means that you can use all DPL formatting options (mode=userformat, listseparators, columns etc.) and pseudo variables (%TITLE%, %PAGE%) to customise the layout of your report.

Technical Note:

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.

allowcachedresults

allowcachedresults allow delivery of results based on cached database contents.

Syntax:

allowcachedresults=true | false | yes+warn

Explanation:

Default is FALSE, so normally DPL will disable the parser cache before it produces a result. Disabling the cache produces some extra server load but guarantees always correct results.

So, if you do not use this parameter you will always get a result which is based on the latest changes made on any articles. But in many cases you could have gotten the same result with using less server resources!

If you set 'allowcachedresults=true', the parser cache will be used. That means, your results might be a little bit outdated (usually one hour or so). But there are less resources used on the server side. You might want to experiment with that parameter and check the size of load reduction (i.e. gain in term of response time).

If you allow cached results you can still enforce DPL to produce a correct result via using "&action=purge" in the command line.

'yes+warn' will use the cache; in addition the result will contain a warning indicating that the result may be out-dated. This is achieved by including the template DPL Cache Warning into the result header. It is up to you to provide a useful text under that name, see e.g. Template:DPL Cache Warning.

reset

reset suppress references to pages, templates, images, categories in DPL output

Syntax:

reset=keyword,.., where keyword is one of:

  • categories
  • templates
  • images
  • links
  • all — a synonym for all of the above

The output of a DPL statement typically creates links to all pages which are part of the result set. The inclusion of contents from other pages via DPL (using 'include') normally has the consequence

  • that the page containing the DPL query becomes part of the categories of the transcluded page
  • that it shares ('adopts') their use of templates
  • that it shares their references to images
  • that it shares their references to other articles.

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.

The reset parameter will suppress all or some of the effects described above.

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

 [[Category:Q Cat]] linking to [[Q Link]] and showing [[Image:Q Image]] and using {{Q Template}}
 ... DPL query which includes contents from other articles.
     assuming that this contents contains links and images, 
              that it uses templates and thatthe articles are part of one or more categories
     RESET statement at the end of the DPL query with one or more of 'categories,templates,images,links'
 ...

In parser extension mode (DPL tag like <DPL>):

reset=categories
will ignore categories of included contents but keep 'own' categories like 'Q Cat'.
reset=images
will throw away references to images contained in included contents but keep 'own' images like 'Q Image'.
reset=templates
will ignore templates used in included contents but keep 'own' template usage ('Q Template').
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 reset on your 'own' links you can use 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.


In parser fuction mode ({{#DPL:....}}):

reset=categories
will ignore all categories
reset=images
will throw away all references to images
reset=templates
will ignore all template invocations
reset=links
will throw away all references to other pages

As you see, using reset 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 reset, you can use eliminate. 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 eliminate. 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.

eliminate

eliminate suppress references to pages, templates, images, categories in DPL output

Syntax:

eliminate=keyword,..

Where keyword is one of:

  • categories
  • templates
  • images
  • links
  • all — a synonym for all of the above

The output of a DPL statement typically creates links to all pages which are part of the result set. The inclusion of contents from other pages via DPL (using include) normally has these consequences:

  • the page containing the DPL query becomes part of the categories of the transcluded page
  • shares ('adopts') their use of templates
  • shares their references to images
  • shares their references to other articles

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.

The eliminate parameter will suppress all or some of the effects described above.

For further explanation see reset.

Please note that the use of eliminate needs a considerable amount of extra computing power as it performs a second parser step for each included document.

debug

debug Sets debugging level.

Syntax:

debug=n, where n is one of:

  • 0 — silent mode, shows nothing
  • 1 — quiet mode, shows (fatal) errors
  • 2 — default mode, like 1 + shows warnings; — (default)
  • 3 — verbose mode, like 2 + shows SQL query.
  • 4 — for internal use only
  • 5 — show Wiki text output from DPL instead of parsed wiki text
  • 6 — show SQL query but DO NOT EXECUTE the query.

If you use debug param but not in first position in the DPL element, the new debug settings are not applied before all previous parameters have been parsed and checked. This will generate a warning for debug=2 and above.

Example: 

<DPL>
  namespace=Media
  debug=0
  namespace=Special
</DPL>

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

DPL debug messages are translatable in DynamicPageList2.i18n.php. See also #Internationalization.

'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 suppresserrors statement.


execandexit

execandexit process the command given as an argument and then exit immediately.

Syntax:

execandexit=command (wiki text)

The wiki text given as an argument will be parsed. After this is done nothing else will happen and DPL will return the result of the command.

Purpose:

The only purpose of this command is to make DPL's URL commandline parameters accesible for other templates.

DPL 1.8.0 and later can take a couple of parameters from the URL command line, like DPL_offset for instance; these parameters can be accessed within DPL via a special syntax: {%DPL_offset%}. This helps to create pages which allow to scroll easily through huge result sets. For example you could write an article called 'MyPopularArticles' containing a DPL query like: 

<dpl>
  category = my popular category
  count=100
  offset={%DPL_offset%}
  columns=3
</dpl>

Calling http://mywebsite/mywiki/index.php?title=MyPopularArticles will give you the first 100 articles in the category. Adding &DPL_offset=100 will give you the next hundred articles. This mechanism can be used to create a generic page scroll feature - provided you can access the value of DPL_offset also in other templates outside DPL. And this is where the execandexit command comes in: it can be used to store the URL parameter in a variable. We use the 'Variables' extension for that purpose, but other constructions are possible. The whole could look like this: 

{{#dpl:execandexit=²{#vardefine:offset¦{%DPL_offset%} }² }}
Showing 100 pages starting from page {{#expr:{{#var:offset}} + 1}}:
<dpl>
  category = my popular category
  count=100
  offset={%DPL_offset%}
  columns=3
</dpl>

Note that we have to use the ²{ ... ¦ ... }² symbols because we want to pass the template invocation to DPL. Had we used standard syntax the MW parser would have expanded the template call to #vardefine before DPL would see it.

See also: Template:Extension DPL scroll

Retrieved from "http://followthescore.org/dpldemo/index.php?title=DPL:Manual_-_DPL_parameters:_Other_parameters&oldid=12326"