summaryrefslogtreecommitdiff
path: root/maintenance/backupPrefetch.inc
blob: cc0a7e170c2cc53ed242429ea1bff53dffcbd3a0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
<?php
/**
 * Helper class for the --prefetch option of dumpTextPass.php
 *
 * Copyright © 2005 Brion Vibber <brion@pobox.com>
 * http://www.mediawiki.org/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 * @ingroup Maintenance
 */

/**
 * Readahead helper for making large MediaWiki data dumps;
 * reads in a previous XML dump to sequentially prefetch text
 * records already normalized and decompressed.
 *
 * This can save load on the external database servers, hopefully.
 *
 * Assumes that dumps will be recorded in the canonical order:
 * - ascending by page_id
 * - ascending by rev_id within each page
 * - text contents are immutable and should not change once
 *   recorded, so the previous dump is a reliable source
 *
 * @ingroup Maintenance
 */
class BaseDump {
	var $reader = null;
	var $atEnd = false;
	var $atPageEnd = false;
	var $lastPage = 0;
	var $lastRev = 0;
	var $infiles = null;

	function BaseDump( $infile ) {
		$this->infiles = explode( ';', $infile );
		$this->reader = new XMLReader();
		$infile = array_shift( $this->infiles );
		if (defined( 'LIBXML_PARSEHUGE' ) ) {
			$this->reader->open( $infile, null, LIBXML_PARSEHUGE );
		}
		else {
			$this->reader->open( $infile );
		}
	}

	/**
	 * Attempts to fetch the text of a particular page revision
	 * from the dump stream. May return null if the page is
	 * unavailable.
	 *
	 * @param $page Integer: ID number of page to read
	 * @param $rev Integer: ID number of revision to read
	 * @return string or null
	 */
	function prefetch( $page, $rev ) {
		$page = intval( $page );
		$rev = intval( $rev );
		while ( $this->lastPage < $page && !$this->atEnd ) {
			$this->debug( "BaseDump::prefetch at page $this->lastPage, looking for $page" );
			$this->nextPage();
		}
		if ( $this->lastPage > $page || $this->atEnd ) {
			$this->debug( "BaseDump::prefetch already past page $page looking for rev $rev  [$this->lastPage, $this->lastRev]" );
			return null;
		}
		while ( $this->lastRev < $rev && !$this->atEnd && !$this->atPageEnd ) {
			$this->debug( "BaseDump::prefetch at page $this->lastPage, rev $this->lastRev, looking for $page, $rev" );
			$this->nextRev();
		}
		if ( $this->lastRev == $rev && !$this->atEnd ) {
			$this->debug( "BaseDump::prefetch hit on $page, $rev [$this->lastPage, $this->lastRev]" );
			return $this->nextText();
		} else {
			$this->debug( "BaseDump::prefetch already past rev $rev on page $page  [$this->lastPage, $this->lastRev]" );
			return null;
		}
	}

	function debug( $str ) {
		wfDebug( $str . "\n" );
		// global $dumper;
		// $dumper->progress( $str );
	}

	/**
	 * @access private
	 */
	function nextPage() {
		if ( $this->skipTo( 'page', 'mediawiki' ) ) {
			if ( $this->skipTo( 'id' ) ) {
				$this->lastPage = intval( $this->nodeContents() );
				$this->lastRev = 0;
				$this->atPageEnd = false;
			}
		} else {
			$this->close();
			if (count($this->infiles)) {
				$infile = array_shift($this->infiles);
				$this->reader->open( $infile );
				$this->atEnd = false;
			}
		}
	}

	/**
	 * @access private
	 */
	function nextRev() {
		if ( $this->skipTo( 'revision' ) ) {
			if ( $this->skipTo( 'id' ) ) {
				$this->lastRev = intval( $this->nodeContents() );
			}
		} else {
			$this->atPageEnd = true;
		}
	}

	/**
	 * @access private
	 * @return string
	 */
	function nextText() {
		$this->skipTo( 'text' );
		return strval( $this->nodeContents() );
	}

	/**
	 * @access private
	 * @param $name string
	 * @param $parent string
	 * @return bool|null
	 */
	function skipTo( $name, $parent = 'page' ) {
		if ( $this->atEnd ) {
			return false;
		}
		while ( $this->reader->read() ) {
			if ( $this->reader->nodeType == XMLReader::ELEMENT &&
				$this->reader->name == $name ) {
				return true;
			}
			if ( $this->reader->nodeType == XMLReader::END_ELEMENT &&
				$this->reader->name == $parent ) {
				$this->debug( "BaseDump::skipTo found </$parent> searching for <$name>" );
				return false;
			}
		}
		return $this->close();
	}

	/**
	 * Shouldn't something like this be built-in to XMLReader?
	 * Fetches text contents of the current element, assuming
	 * no sub-elements or such scary things.
	 *
	 * @return String
	 * @access private
	 */
	function nodeContents() {
		if ( $this->atEnd ) {
			return null;
		}
		if ( $this->reader->isEmptyElement ) {
			return "";
		}
		$buffer = "";
		while ( $this->reader->read() ) {
			switch( $this->reader->nodeType ) {
			case XMLReader::TEXT:
//			case XMLReader::WHITESPACE:
			case XMLReader::SIGNIFICANT_WHITESPACE:
				$buffer .= $this->reader->value;
				break;
			case XMLReader::END_ELEMENT:
				return $buffer;
			}
		}
		return $this->close();
	}

	/**
	 * @access private
	 * @return null
	 */
	function close() {
		$this->reader->close();
		$this->atEnd = true;
		return null;
	}
}