node_revision_history.module

<?php
/**
 * @file
 * This module allows administrators to review the number of node
 * revisions current in the site and make use of Backdrop's
 * function node_revision_delete for selective deletion of them.
 */


/**
* Implements hook_menu().
*/
function node_revision_history_menu() {
  $items['admin/content/node_revision_history'] = array(
    'title' => 'Node Revision History',
    'description' => 'Listing of node revisions.',
    'page callback' => 'backdrop_get_form',
    'page arguments' => array('node_revision_history_listing_form'),
    'access callback' => 'user_access',
    'access arguments' => array('administer node_revision_history'),
    'type' => MENU_NORMAL_ITEM,
  );

  return $items;
}

/**
 * Implements hook_permission().
 */
function node_revision_history_permission() {
  return array(
    'administer node_revision_history' => array(
      'title' => t('Administer Node History'),
      'description' => t('Allow access to use the module.'),
    ),
  );
}

/**
 * The Node Revision History initial form.
 */
function node_revision_history_listing_form($form, &$form_state) {

  // Display page 2 if $form_state['page_num'] == 2
  if (!empty($form_state['page_num']) && $form_state['page_num'] == 2) {
    return node_revision_history_listing_form_page_two($form, $form_state);
  }

  // Display page 3 if $form_state['page_num'] == 3
  if (!empty($form_state['page_num']) && $form_state['page_num'] == 3) {
    return node_revision_history_listing_form_page_three($form, $form_state);
  }

  // Otherwise we build page 1.
  $form_state['page_num'] = 1;

  $form['help'] = array(
    '#type' => 'help',
    '#suffix' => t('Important: make sure you have backed up your database before using this utilty.'),
    '#markup' => t('This utility provides a quick way for admin to review the number of revisions 
      stored in the system for individual nodes and to delete some or all of them.'),
  );
  $form['description'] = array(
    '#type' => 'item',
    '#title' => t('Specify either a single node identity number to process one node or use zero to get a full listing'),
    '#description' => t('Submitting zero will produce a table listing current node types and number of revisions.'),
  );

  $form['nid'] = array(
    '#type' => 'textfield',
    '#title' => t('Node identity - NID'),
    '#default_value' => 0,
    '#size' => 10,
    '#maxlength' => 10,
  );

  $form['threshold'] = array(
    '#type' => 'textfield',
    '#title' => t('Revision threshold'),
    '#description' => t('When generating the table of results only include nodes 
      which have more revisions than this threshold.'),
    '#default_value' => 1,
    '#size' => 10,
    '#maxlength' => 10,
  );

  $form['next'] = array(
    '#type' => 'submit',
    '#value' => 'Next >>',
    '#submit' => array('node_revision_history_listing_form_next_submit'),
  );

  return $form;
}


/**
 * Submit handler for node_revision_history_listing_form() next button.
 *
 * Capture the values from page one and store them away so they can be used
 * at final submit time.
 */
function node_revision_history_listing_form_next_submit($form, &$form_state) {
  $form_state['page_values'][1] = $form_state['values'];

  if (!empty($form_state['page_values'][2])) {
    $form_state['values'] = $form_state['page_values'][2];
  }

  // When form rebuilds, it will look at this to figure which page to build.
  if ($form_state['values']['nid'] == 0) {
    $form_state['page_num'] = 3;
  }
  else {
    $form_state['page_num'] = 2;
  }
  $form_state['rebuild'] = TRUE;
}


/**
 * The form for the second page of form_node_revision_history_listing().
 * This form is for reviewing a specified node.
 */
function node_revision_history_listing_form_page_two($form, &$form_state) {

  $this_nid = $form_state['values']['nid'];
  $this_node = node_load($this_nid);
  $revisions = node_revision_list($this_node);

  // Produce a table of results.
  $headers = array(
    'VID',
    'Author',
    'Created',
  );

  $options = array();

  foreach ($revisions as $vid => $data) {
    $options[$vid] = array(
      array('data' => $data -> vid),
      array('data' => $data-> name),
      array('data' => date('Y-m-d H:i', $data-> timestamp)),
    );
    // For each revision identify the current one, others are given value 0.
    $form_state['current_vid'][$vid] = $data -> vid == $data -> current_vid ? $data -> current_vid : 0;
  }

  $form['description'] = array(
    '#type' => 'item',
    '#title' => "Select revisions of node $this_nid to delete.",
    '#description' => 'NB. The procedure will prevent the deletion of the current revision (the first in this list).',
  );

  $form['revisions'] = array(
    '#type' => 'tableselect',
    '#header' => $headers,
    '#options' => $options,
    '#empty' => t('No content available.'),
  );

  $form['actions'] = array('#type' => 'actions');
  $form['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Submit'),
    '#submit' => array('node_revision_history_listing_form_page_two_submit'),
  );

  $form['back'] = array(
    '#type' => 'submit',
    '#value' => t('<< Back'),
    '#submit' => array('node_revision_history_listing_form_page_two_back'),
    '#limit_validation_errors' => array(),
  );

  return $form;
}


function node_revision_history_listing_form_page_two_submit($form, &$form_state) {
  // Get node identities.
  $revisions = $form_state['values']['revisions'];
  $vids = $form_state['current_vid'];

  $deleted_vids = '';
  foreach($revisions as $revision => $value){
    if($value > 0){
      node_revision_delete($value);
      $deleted_vids =  trim($value) . ', ' . $deleted_vids;
    }
  }
  backdrop_set_message(t('The following revisions have been deleted, VIDs = @deleted_vids',
    array(
      '@deleted_vids' => $deleted_vids,
    )
  ));
}


/**
 * Back button handler submit handler.
 *
 * Since #limit_validation_errors = array() is set, values from page 2
 * will be discarded. We load the page 1 values instead.
 */
function node_revision_history_listing_form_page_two_back($form, &$form_state) {
  $form_state['values'] = $form_state['page_values'][1];
  $form_state['page_num'] = 1;
  $form_state['rebuild'] = TRUE;
}

/**
 * The form for the third page of form_node_revision_history_listing().
 * This lists the number of revisions for every node in the system
 * where that number exceeds the threshold.
 * It provides a checkbox for specifying which nodes should have some
 * revisions deleted and when submitted processes the selection.
 */
function node_revision_history_listing_form_page_three($form, &$form_state) {
  $revision_count = array();
  $threshold = $form_state['values']['threshold'];

  //for each node type count how many revision exist.
  foreach (node_type_get_names() as $type => $name) {
    $revisions = node_revision_history_candidates($type, $threshold);
    if(!empty($revisions)){
      $revision_count[$name] = $revisions;
    }
  }
  $rows = array();

  foreach ($revision_count as $name => $data) {
    foreach ($data as $identity => $revisions) {
      $rows[$identity] = array(
        'name' => $name,
        'identity' => $identity,
        'number' => $revisions,
      );
    }
  }
  $form_state['revision_data'] = $rows;
  $form_state['threshold'] = $threshold;

  $options = array();

  foreach ($rows as $rid => $revisions) {
    $options[$rid] = array(
      array('data' => $revisions['name']),
      array('data' => $revisions['identity']),
      array('data' => $revisions['number']),
    );
  }

  // Produce a table of results.
  $headers = array(
    'Node type',
    'Node identity',
    'Number of revisions',
  );

  $form['description'] = array(
    '#type' => 'item',
    '#title' => t('Table of existing revisions with number greater than threshold.'),
    '#description' => t('Choose one or more nodes to process. The more recent revisions 
    will not be deleted, depending on the value of the threshold.'),
  );
  
  $form['d_threshold'] = array(
    '#type' => 'textfield',
    '#title' => t('Deletion threshold'),
    '#description' => t('Delete revisions in excess of this threshold.'),
    '#default_value' => $threshold,
    '#size' => 10,
    '#maxlength' => 10,
  );

  $form['revisions'] = array(
    '#type' => 'tableselect',
    '#header' => $headers,
    '#options' => $options,
    '#empty' => t('No content available.'),
  );

  $form['back'] = array(
    '#type' => 'submit',
    '#value' => t('<< Back'),
    '#submit' => array('node_revision_history_listing_form_page_three_back'),
  );

  $form['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Submit'),
    '#submit' => array('node_revision_history_listing_form_page_three_submit'),
  );

  return $form;
}


/**
 * Submit function for the third page of form_node_revision_history_listing().
 */
function node_revision_history_listing_form_page_three_submit($form, &$form_state) {
  // Get IDs of nodes to process from $form_state['values']['revisions'] > 0.
  // Get corresponding node data from $form_state['revision_data'].
  // Build an array of data for selected nodes ready for use of
  // function node_revision_delete() limited by value of threshold in
  // $form_state['threshold'].

  $data = $form_state['revision_data'];

  $d_threshold = $form_state['values']['d_threshold'];
  // List nodes with revisions to delete
  $nodes = array();
  $no_nodes = TRUE;
  foreach ($form_state['values']['revisions'] as $nid => $value) {
    if ($value > 0) {
      $nodes[$nid] = $nid;
      $no_nodes = FALSE;
    }
  }
  if ($no_nodes) {
    // return to initial page.
    $form_state['page_num'] = 1;
    $form_state['rebuild'] = TRUE;
    backdrop_set_message(t('No nodes to process.'));
    return;
  }
  foreach ($nodes as $node => $item) {
    // Now obtain the number of revisions for each node listed.
    $nid = $data[$item]['identity'];
    $this_node = node_load($nid);
    $revisions_list = node_revision_list($this_node);
    // step through revisions_list with a count,
    // do nothing until count reaches threshold
    // then delete each revision
    // this relies on revisions being listed in descending order
    // $revisions_list is an array of node objects.
    // Note: function node_revision_delete includes a check that
    // prevents deleting the current revision.
    $n = 0;
    foreach ($revisions_list as $vid => $revision) {
      if ($n >= $d_threshold){
        node_revision_delete($vid);
      }
      $n++;
    }
  }
  backdrop_set_message(t('Processing complete.'));
}


function node_revision_history_listing_form_page_three_back($form, &$form_state) {
  $form_state['values'] = $form_state['page_values'][1];
  $form_state['page_num'] = 1;
  $form_state['rebuild'] = TRUE;
}


/**
 * Helper function to return the list of nids with revisions.
 *
 * @param string $content_type
 *   A content type machine name.
 *
 * @return array
 *   Array of nids with number of revisions for each
 */
function node_revision_history_candidates($content_type, $threshold) {
  $params = array(
    ':content_type' => $content_type,
    ':threshold' => $threshold,
  );
  $result = db_query("SELECT n.nid, COUNT(r.nid)
                     FROM {node} n
                     INNER JOIN {node_revision} r ON r.nid = n.nid
                     WHERE n.type = :content_type
                     GROUP BY n.nid
                     HAVING count(r.nid) > :threshold", $params)->fetchAllKeyed();
  return $result;
}