function pager_query in Drupal 6

Same name and namespace in other branches

1. 4 includes/pager.inc \pager_query()
2. 5 includes/pager.inc \pager_query()

Perform a paged database query.

Use this function when doing select queries you wish to be able to page. The pager uses LIMIT-based queries to fetch only the records required to render a certain page. However, it has to learn the total number of records returned by the query to compute the number of pages (the number of records / records per page). This is done by inserting "COUNT(*)" in the original query. For example, the query "SELECT nid, type FROM node WHERE status = '1' ORDER BY sticky DESC, created DESC" would be rewritten to read "SELECT COUNT(*) FROM node WHERE status = '1' ORDER BY sticky DESC, created DESC". Rewriting the query is accomplished using a regular expression.

Unfortunately, the rewrite rule does not always work as intended for queries that already have a "COUNT(*)" or a "GROUP BY" clause, and possibly for other complex queries. In those cases, you can optionally pass a query that will be used to count the records.

For example, if you want to page the query "SELECT COUNT(*), TYPE FROM node GROUP BY TYPE", pager_query() would invoke the incorrect query "SELECT COUNT(*) FROM node GROUP BY TYPE". So instead, you should pass "SELECT COUNT(DISTINCT(TYPE)) FROM node" as the optional $count_query parameter.

Parameters

$query: The SQL query that needs paging.

$limit: The number of query results to display per page.

$element: An optional integer to distinguish between multiple pagers on one page.

$count_query: An SQL query used to count matching records.

...: A variable number of arguments which are substituted into the query (and the count query) using printf() syntax. Instead of a variable number of query arguments, you may also pass a single array containing the query arguments.

Return value

A database query result resource, or FALSE if the query was not executed correctly.

Related topics

28 calls to pager_query()

aggregator_feed_items_load in modules/aggregator/aggregator.pages.inc

Load feed items by passing a SQL query.

blog_page_last in modules/blog/blog.pages.inc

Menu callback; displays a Drupal page containing recent blog entries of all users.

blog_page_user in modules/blog/blog.pages.inc

Menu callback; displays a Drupal page containing recent blog entries of a given user.

comment_admin_overview in modules/comment/comment.admin.inc

Form builder; Builds the comment overview form for the admin.

comment_render in modules/comment/comment.module

Renders comment(s).

... See full list

1 string reference to 'pager_query'

drupal_error_handler in includes/common.inc

Log errors as defined by administrator.

File

includes/pager.inc, line 50

Functions to aid in presenting database results as a set of pages.

Code

function pager_query($query, $limit = 10, $element = 0, $count_query = NULL) {
  global $pager_page_array, $pager_total, $pager_total_items;
  $page = isset($_GET['page']) ? $_GET['page'] : '';

  // Substitute in query arguments.
  $args = func_get_args();
  $args = array_slice($args, 4);

  // Alternative syntax for '...'
  if (isset($args[0]) && is_array($args[0])) {
    $args = $args[0];
  }

  // Construct a count query if none was given.
  if (!isset($count_query)) {
    $count_query = preg_replace(array(
      '/SELECT.*?FROM /As',
      '/ORDER BY .*/',
    ), array(
      'SELECT COUNT(*) FROM ',
      '',
    ), $query);
  }

  // Convert comma-separated $page to an array, used by other functions.
  $pager_page_array = explode(',', $page);

  // We calculate the total of pages as ceil(items / limit).
  $pager_total_items[$element] = db_result(db_query($count_query, $args));
  $pager_total[$element] = ceil($pager_total_items[$element] / $limit);
  $pager_page_array[$element] = max(0, min((int) $pager_page_array[$element], (int) $pager_total[$element] - 1));
  return db_query_range($query, $args, $pager_page_array[$element] * $limit, $limit);
}