lib/dml/pgsql_native_moodle_recordset.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * Native postgresql recordset.
  19  *
  20  * @package    core_dml
  21  * @copyright  2008 Petr Skoda (http://skodak.org)
  22  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  23  */
  24
  25 defined('MOODLE_INTERNAL') || die();
  26
  27 require_once(__DIR__.'/moodle_recordset.php');
  28
  29 /**
  30  * pgsql specific moodle recordset class
  31  *
  32  * @package    core_dml
  33  * @copyright  2008 Petr Skoda (http://skodak.org)
  34  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  35  */
  36 class pgsql_native_moodle_recordset extends moodle_recordset {
  37
  38     protected $result;
  39     /** @var current row as array.*/
  40     protected $current;
  41     protected $blobs = array();
  42
  43     /** @var string Name of cursor or '' if none */
  44     protected $cursorname;
  45
  46     /** @var pgsql_native_moodle_database Postgres database resource */
  47     protected $db;
  48
  49     /** @var bool True if there are no more rows to fetch from the cursor */
  50     protected $lastbatch;
  51
  52     /**
  53      * Build a new recordset to iterate over.
  54      *
  55      * When using cursors, $result will be null initially.
  56      *
  57      * @param resource|null $result A pg_query() result object to create a recordset from.
  58      * @param pgsql_native_moodle_database $db Database object (only required when using cursors)
  59      * @param string $cursorname Name of cursor or '' if none
  60      */
  61     public function __construct($result, pgsql_native_moodle_database $db = null, $cursorname = '') {
  62         if ($cursorname && !$db) {
  63             throw new coding_exception('When specifying a cursor, $db is required');
  64         }
  65         $this->result = $result;
  66         $this->db = $db;
  67         $this->cursorname = $cursorname;
  68
  69         // When there is a cursor, do the initial fetch.
  70         if ($cursorname) {
  71             $this->fetch_cursor_block();
  72         }
  73
  74         // Find out if there are any blobs.
  75         $numfields = pg_num_fields($this->result);
  76         for ($i = 0; $i < $numfields; $i++) {
  77             $type = pg_field_type($this->result, $i);
  78             if ($type == 'bytea') {
  79                 $this->blobs[] = pg_field_name($this->result, $i);
  80             }
  81         }
  82
  83         $this->current = $this->fetch_next();
  84     }
  85
  86     /**
  87      * Fetches the next block of data when using cursors.
  88      *
  89      * @throws coding_exception If you call this when the fetch buffer wasn't freed yet
  90      */
  91     protected function fetch_cursor_block() {
  92         if ($this->result) {
  93             throw new coding_exception('Unexpected non-empty result when fetching from cursor');
  94         }
  95         list($this->result, $this->lastbatch) = $this->db->fetch_from_cursor($this->cursorname);
  96         if (!$this->result) {
  97             throw new coding_exception('Unexpected failure when fetching from cursor');
  98         }
  99     }
 100
 101     public function __destruct() {
 102         $this->close();
 103     }
 104
 105     private function fetch_next() {
 106         if (!$this->result) {
 107             return false;
 108         }
 109         if (!$row = pg_fetch_assoc($this->result)) {
 110             // There are no more rows in this result.
 111             pg_free_result($this->result);
 112             $this->result = null;
 113
 114             // If using a cursor, can we fetch the next block?
 115             if ($this->cursorname && !$this->lastbatch) {
 116                 $this->fetch_cursor_block();
 117                 if (!$row = pg_fetch_assoc($this->result)) {
 118                     pg_free_result($this->result);
 119                     $this->result = null;
 120                     return false;
 121                 }
 122             } else {
 123                 return false;
 124             }
 125         }
 126
 127         if ($this->blobs) {
 128             foreach ($this->blobs as $blob) {
 129                 $row[$blob] = $row[$blob] !== null ? pg_unescape_bytea($row[$blob]) : null;
 130             }
 131         }
 132
 133         return $row;
 134     }
 135
 136     public function current() {
 137         return (object)$this->current;
 138     }
 139
 140     public function key() {
 141         // return first column value as key
 142         if (!$this->current) {
 143             return false;
 144         }
 145         $key = reset($this->current);
 146         return $key;
 147     }
 148
 149     public function next() {
 150         $this->current = $this->fetch_next();
 151     }
 152
 153     public function valid() {
 154         return !empty($this->current);
 155     }
 156
 157     public function close() {
 158         if ($this->result) {
 159             pg_free_result($this->result);
 160             $this->result  = null;
 161         }
 162         $this->current = null;
 163         $this->blobs   = null;
 164
 165         // If using cursors, close the cursor.
 166         if ($this->cursorname) {
 167             $this->db->close_cursor($this->cursorname);
 168             $this->cursorname = null;
 169         }
 170     }
 171 }