<?php
/**
 * ARC2 RDF Store DELETE Query Handler
 *
 * @author Benjamin Nowack <bnowack@semsol.com>
 * @license http://arc.semsol.org/license
 * @homepage <http://arc.semsol.org/>
 * @package ARC2
 * @version 2010-04-11
*/

ARC2::inc('StoreQueryHandler');

class ARC2_StoreDeleteQueryHandler extends ARC2_StoreQueryHandler {

  function __construct($a = '', &$caller) {/* caller has to be a store */
    parent::__construct($a, $caller);
  }
  
  function ARC2_StoreDeleteQueryHandler($a = '', &$caller) {
    $this->__construct($a, $caller);
  }

  function __init() {/* db_con */
    parent::__init();
    $this->store =& $this->caller;
    $this->handler_type = 'delete';
  }

  /*  */
  
  function runQuery($infos) {
    $this->infos = $infos;
    $con = $this->store->getDBCon();
    $t1 = ARC2::mtime();
    /* delete */
    $this->refs_deleted = false;
    /* graph(s) only */
    if (!$this->v('construct_triples', array(), $this->infos['query'])) {
      $tc = $this->deleteTargetGraphs();
    }
    /* graph(s) + explicit triples */
    elseif (!$this->v('pattern', array(), $this->infos['query'])) {
      $tc = $this->deleteTriples();
    }
    /* graph(s) + constructed triples */
    else {
      $tc = $this->deleteConstructedGraph();
    }
    $t2 = ARC2::mtime();
    /* clean up */
    if ($tc && ($this->refs_deleted || (rand(1, 100) == 1))) $this->cleanTableReferences();
    if ($tc && (rand(1, 50) == 1)) $this->store->optimizeTables();
    if ($tc && (rand(1, 500) == 1)) $this->cleanValueTables();
    $t3 = ARC2::mtime();
    $index_dur = round($t3 - $t2, 4);
    $dur = round($t3 - $t1, 4);
    return array(
      't_count' => $tc,
      'delete_time' => $dur,
      'index_update_time' => $index_dur,
    );
  }
  
  /*  */

  function deleteTargetGraphs() {
    $tbl_prefix = $this->store->getTablePrefix();
    $r = 0;
    $con = $this->store->getDBCon();
    foreach ($this->infos['query']['target_graphs'] as $g) {
      if ($g_id = $this->getTermID($g, 'g')) {
        $rs = mysql_query('DELETE FROM ' . $tbl_prefix . 'g2t WHERE g = ' .$g_id, $con);
        $r += mysql_affected_rows($con);
      }
    }
    $this->refs_deleted = $r ? 1 : 0;
    return $r;
  }
  
  /*  */
  
  function deleteTriples() {
    $r = 0;
    $dbv = $this->store->getDBVersion();
    $tbl_prefix = $this->store->getTablePrefix();
    $con = $this->store->getDBCon();
    /* graph restriction */
    $tgs = $this->infos['query']['target_graphs'];
    $gq = '';
    foreach ($tgs as $g) {
      if ($g_id = $this->getTermID($g, 'g')) {
        $gq .= $gq ? ', ' . $g_id : $g_id;
      }
    }
    $gq = $gq ? ' AND G.g IN (' . $gq . ')' : '';
    /* triples */
    foreach ($this->infos['query']['construct_triples'] as $t) {
      $q = '';
      $skip = 0;
      foreach (array('s', 'p', 'o') as $term) {
        if (isset($t[$term . '_type']) && preg_match('/(var)/', $t[$term . '_type'])) {
          //$skip = 1;
        }
        else {
          $term_id = $this->getTermID($t[$term], $term);
          $q .= ($q ? ' AND ' : '') . 'T.' . $term . '=' . $term_id;
          /* explicit lang/dt restricts the matching */
          if ($term == 'o') {
            $o_lang = $this->v1('o_lang', '', $t);
            $o_lang_dt = $this->v1('o_datatype', $o_lang, $t);
            if ($o_lang_dt) {
              $q .= ($q ? ' AND ' : '') . 'T.o_lang_dt=' . $this->getTermID($o_lang_dt, 'lang_dt');
            }
          }
        }
      }
      if ($skip) {
        continue;
      }
      if ($gq) {
        $sql = ($dbv < '04-01') ? 'DELETE ' . $tbl_prefix . 'g2t' : 'DELETE G';
        $sql .= '
          FROM ' . $tbl_prefix . 'g2t G 
          JOIN ' . $this->getTripleTable() . ' T ON (T.t = G.t' . $gq . ')
          WHERE ' . $q . '
        ';
        $this->refs_deleted = 1;
      }
      else {/* triples only */
        $sql = ($dbv < '04-01') ? 'DELETE ' . $this->getTripleTable() : 'DELETE T';
        $sql .= ' FROM ' . $this->getTripleTable() . ' T WHERE ' . $q;
      }
      $rs = mysql_query($sql, $con);
      if ($er = mysql_error($con)) {
        $this->addError($er .' in ' . $sql);
      }
      $r += mysql_affected_rows($con);
    }
    return $r;
  }
  
  /*  */
  
  function deleteConstructedGraph() {
    ARC2::inc('StoreConstructQueryHandler');
    $h =& new ARC2_StoreConstructQueryHandler($this->a, $this->store);
    $sub_r = $h->runQuery($this->infos);
    $triples = ARC2::getTriplesFromIndex($sub_r);
    $tgs = $this->infos['query']['target_graphs'];
    $this->infos = array('query' => array('construct_triples' => $triples, 'target_graphs' => $tgs));
    return $this->deleteTriples();
  }
  
  /*  */
  
  function cleanTableReferences() {
    /* lock */
    if (!$this->store->getLock()) return $this->addError('Could not get lock in "cleanTableReferences"');
    $con = $this->store->getDBCon();
    $tbl_prefix = $this->store->getTablePrefix();
    $dbv = $this->store->getDBVersion();
    /* check for unconnected triples */
    $sql = '
      SELECT T.t FROM '. $tbl_prefix . 'triple T LEFT JOIN '. $tbl_prefix . 'g2t G ON ( G.t = T.t )
      WHERE G.t IS NULL LIMIT 1
    ';
    if (($rs = mysql_query($sql, $con)) && mysql_num_rows($rs)) {
      /* delete unconnected triples */
      $sql = ($dbv < '04-01') ? 'DELETE ' . $tbl_prefix . 'triple' : 'DELETE T';
      $sql .= '
        FROM ' . $tbl_prefix . 'triple T 
        LEFT JOIN ' . $tbl_prefix . 'g2t G ON (G.t = T.t)
        WHERE G.t IS NULL
      ';
      mysql_query($sql, $con);
    }
    /* check for unconnected graph refs */
    if ((rand(1, 10) == 1)) {
      $sql = '
        SELECT G.g FROM '. $tbl_prefix . 'g2t G LEFT JOIN '. $tbl_prefix . 'triple T ON ( T.t = G.t )
        WHERE T.t IS NULL LIMIT 1
      ';
      if (($rs = mysql_query($sql, $con)) && mysql_num_rows($rs)) {
        /* delete unconnected graph refs */
        $sql = ($dbv < '04-01') ? 'DELETE ' . $tbl_prefix . 'g2t' : 'DELETE G';
        $sql .= '
          FROM ' . $tbl_prefix . 'g2t G 
          LEFT JOIN ' . $tbl_prefix . 'triple T ON (T.t = G.t)
          WHERE T.t IS NULL
        ';
        mysql_query($sql, $con);
      }
    }
    /* release lock */
    $this->store->releaseLock();
  }
  
  /*  */

  function cleanValueTables() {
    /* lock */
    if (!$this->store->getLock()) return $this->addError('Could not get lock in "cleanValueTables"');
    $con = $this->store->getDBCon();
    $tbl_prefix = $this->store->getTablePrefix();
    $dbv = $this->store->getDBVersion();
    /* o2val */
    $sql = ($dbv < '04-01') ? 'DELETE ' . $tbl_prefix . 'o2val' : 'DELETE V';
    $sql .= '
      FROM ' . $tbl_prefix . 'o2val V 
      LEFT JOIN ' . $tbl_prefix . 'triple T ON (T.o = V.id)
      WHERE T.t IS NULL
    ';
    mysql_query($sql, $con);
    /* s2val */
    $sql = ($dbv < '04-01') ? 'DELETE ' . $tbl_prefix . 's2val' : 'DELETE V';
    $sql .= '
      FROM ' . $tbl_prefix . 's2val V 
      LEFT JOIN ' . $tbl_prefix . 'triple T ON (T.s = V.id)
      WHERE T.t IS NULL
    ';
    mysql_query($sql, $con);
    /* id2val */
    $sql = ($dbv < '04-01') ? 'DELETE ' . $tbl_prefix . 'id2val' : 'DELETE V';
    $sql .= '
      FROM ' . $tbl_prefix . 'id2val V 
      LEFT JOIN ' . $tbl_prefix . 'g2t G ON (G.g = V.id)
      LEFT JOIN ' . $tbl_prefix . 'triple T1 ON (T1.p = V.id)
      LEFT JOIN ' . $tbl_prefix . 'triple T2 ON (T2.o_lang_dt = V.id)
      WHERE G.g IS NULL AND T1.t IS NULL AND T2.t IS NULL
    ';
    //mysql_query($sql, $con);
  }
  
  /*  */

}