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     /** @var PgSql\Result|resource|null */
  39     protected $result;
  40     /** @var current row as array.*/
  41     protected $current;
  42     protected $blobs = array();
  43
  44     /** @var string Name of cursor or '' if none */
  45     protected $cursorname;
  46
  47     /** @var pgsql_native_moodle_database Postgres database resource */
  48     protected $db;
  49
  50     /** @var bool True if there are no more rows to fetch from the cursor */
  51     protected $lastbatch;
  52
  53     /**
  54      * Build a new recordset to iterate over.
  55      *
  56      * When using cursors, $result will be null initially.
  57      *
  58      * @param resource|PgSql\Result|null $result A pg_query() result object to create a recordset from.
  59      * @param pgsql_native_moodle_database $db Database object (only required when using cursors)
  60      * @param string $cursorname Name of cursor or '' if none
  61      */
  62     public function __construct($result, pgsql_native_moodle_database $db = null, $cursorname = '') {
  63         if ($cursorname && !$db) {
  64             throw new coding_exception('When specifying a cursor, $db is required');
  65         }
  66         $this->result = $result;
  67         $this->db = $db;
  68         $this->cursorname = $cursorname;
  69
  70         // When there is a cursor, do the initial fetch.
  71         if ($cursorname) {
  72             $this->fetch_cursor_block();
  73         }
  74
  75         // Find out if there are any blobs.
  76         $numfields = pg_num_fields($this->result);
  77         for ($i = 0; $i < $numfields; $i++) {
  78             $type = $this->db->pg_field_type($this->result, $i);
  79             if ($type == 'bytea') {
  80                 $this->blobs[] = pg_field_name($this->result, $i);
  81             }
  82         }
  83
  84         $this->current = $this->fetch_next();
  85     }
  86
  87     /**
  88      * Fetches the next block of data when using cursors.
  89      *
  90      * @throws coding_exception If you call this when the fetch buffer wasn't freed yet
  91      */
  92     protected function fetch_cursor_block() {
  93         if ($this->result) {
  94             throw new coding_exception('Unexpected non-empty result when fetching from cursor');
  95         }
  96         list($this->result, $this->lastbatch) = $this->db->fetch_from_cursor($this->cursorname);
  97         if (!$this->result) {
  98             throw new coding_exception('Unexpected failure when fetching from cursor');
  99         }
 100     }
 101
 102     public function __destruct() {
 103         $this->close();
 104     }
 105
 106     private function fetch_next() {
 107         if (!$this->result) {
 108             return false;
 109         }
 110         if (!$row = pg_fetch_assoc($this->result)) {
 111             // There are no more rows in this result.
 112             pg_free_result($this->result);
 113             $this->result = null;
 114
 115             // If using a cursor, can we fetch the next block?
 116             if ($this->cursorname && !$this->lastbatch) {
 117                 $this->fetch_cursor_block();
 118                 if (!$row = pg_fetch_assoc($this->result)) {
 119                     pg_free_result($this->result);
 120                     $this->result = null;
 121                     return false;
 122                 }
 123             } else {
 124                 return false;
 125             }
 126         }
 127
 128         if ($this->blobs) {
 129             foreach ($this->blobs as $blob) {
 130                 $row[$blob] = $row[$blob] !== null ? pg_unescape_bytea($row[$blob]) : null;
 131             }
 132         }
 133
 134         return $row;
 135     }
 136
 137     public function current(): stdClass {
 138         return (object)$this->current;
 139     }
 140
 141     #[\ReturnTypeWillChange]
 142     public function key() {
 143         // return first column value as key
 144         if (!$this->current) {
 145             return false;
 146         }
 147         $key = reset($this->current);
 148         return $key;
 149     }
 150
 151     public function next(): void {
 152         $this->current = $this->fetch_next();
 153     }
 154
 155     public function valid(): bool {
 156         return !empty($this->current);
 157     }
 158
 159     public function close() {
 160         if ($this->result) {
 161             pg_free_result($this->result);
 162             $this->result  = null;
 163         }
 164         $this->current = null;
 165         $this->blobs   = null;
 166
 167         // If using cursors, close the cursor.
 168         if ($this->cursorname) {
 169             $this->db->close_cursor($this->cursorname);
 170             $this->cursorname = null;
 171         }
 172     }
 173 }