DPL Example 027

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Optimum performance result scrolling for huge wikis

This page demonstrates how DPL can be used in really huge wikis like WIKIPEDIA to allow efficient scrolling through huge result sets. The approach ios very much straight forward:

  • We use count=50
  • When scrolling forward we use ascending order; when scrolling backward we internally use descending order but we reverse the result set for the user
  • Each query takes a lower or an upper limit for the search as a selection criterion; This criterion is set by an URL parameter which is deducted from information of the previous query: each query passes the first and last page of its result set to a scroll helper template.
  • The approach could be extended: The scroll helper could produce a set of fixed links for the initial letters; thus one could easily jump to A, B, C, ...
  • For convenience we repeat the last page of a result set as the first page of the next result set.
  • Note that adding %TOTALPAGES% to resultsheader or resultsfooter would lead to a SQL statement which might be less efficient as the database must each time calculate the total number of matching records ("SQL_CALC_FOUND_ROWS")
  • The time spent within DPL is displayed at the bottom; usually it is below 30 msec.
startbacknext(50 listedExpression error: Unexpected > operator.)
startbacknext(50 listedExpression error: Unexpected > operator.)
0.002 sec. (2024/11/24 09:40:43) 
{{#dpl:
| namespace          =
| redirects          = include
| count              = {%DPL_count:50%}
| resultsheader      = ²{Extension DPL continue¦dir=%SCROLLDIR%¦pages=%PAGES%¦total=¦firsttitle=%FIRSTTITLE%¦lasttitle=%LASTTITLE%¦page={{FULLPAGENAME}}}²\n
| resultsfooter      = ²{Extension DPL continue¦dir=%SCROLLDIR%¦pages=%PAGES%¦total=¦firsttitle=%FIRSTTITLE%¦lasttitle=%LASTTITLE%¦page={{FULLPAGENAME}}}² %DPLTIME%\n
}}
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