const FOR_THIS_USER = 2;
const RAW = 3;
+ const TEXT_CACHE_GROUP = 'revisiontext:10'; // process cache name and max key count
+
/**
* Load a page revision from a given revision ID number.
* Returns null if no such revision can be found.
* @return string|bool The revision's text, or false on failure
*/
private function loadText() {
- // Caching may be beneficial for massive use of external storage
global $wgRevisionCacheExpiry;
- static $processCache = null;
-
- if ( !$wgRevisionCacheExpiry ) {
- return $this->fetchText();
- }
-
- if ( !$processCache ) {
- $processCache = new MapCacheLRU( 10 );
- }
$cache = ObjectCache::getMainWANInstance();
- $key = $cache->makeKey( 'revisiontext', 'textid', $this->getTextId() );
+ if ( $cache->getQoS( $cache::ATTR_EMULATION ) <= $cache::QOS_EMULATION_SQL ) {
+ // Do not cache RDBMs blobs in...the RDBMs store
+ $ttl = $cache::TTL_UNCACHEABLE;
+ } else {
+ $ttl = $wgRevisionCacheExpiry ?: $cache::TTL_UNCACHEABLE;
+ }
// No negative caching; negative hits on text rows may be due to corrupted replica DBs
- return $processCache->getWithSetCallback( $key, function () use ( $cache, $key ) {
- global $wgRevisionCacheExpiry;
-
- return $cache->getWithSetCallback(
- $key,
- $wgRevisionCacheExpiry,
- function () {
- return $this->fetchText();
- }
- );
- } );
+ return $cache->getWithSetCallback(
+ $cache->makeKey( 'revisiontext', 'textid', $this->getTextId() ),
+ $ttl,
+ function () {
+ return $this->fetchText();
+ },
+ [ 'pcGroup' => self::TEXT_CACHE_GROUP, 'pcTTL' => $cache::TTL_PROC_LONG ]
+ );
}
private function fetchText() {
$row = null;
}
+ // Callers doing updates will pass in READ_LATEST as usual. Since the text/blob tables
+ // do not normally get rows changed around, set READ_LATEST_IMMUTABLE in those cases.
+ $flags = $this->mQueryFlags;
+ $flags |= DBAccessObjectUtils::hasFlags( $flags, self::READ_LATEST )
+ ? self::READ_LATEST_IMMUTABLE
+ : 0;
+
+ list( $index, $options, $fallbackIndex, $fallbackOptions ) =
+ DBAccessObjectUtils::getDBOptions( $flags );
+
if ( !$row ) {
// Text data is immutable; check replica DBs first.
- $dbr = wfGetDB( DB_REPLICA );
- $row = $dbr->selectRow( 'text',
+ $row = wfGetDB( $index )->selectRow(
+ 'text',
[ 'old_text', 'old_flags' ],
[ 'old_id' => $textId ],
- __METHOD__ );
+ __METHOD__,
+ $options
+ );
}
- // Fallback to the master in case of replica DB lag. Also use FOR UPDATE if it was
- // used to fetch this revision to avoid missing the row due to REPEATABLE-READ.
- $forUpdate = ( $this->mQueryFlags & self::READ_LOCKING == self::READ_LOCKING );
- if ( !$row && ( $forUpdate || wfGetLB()->getServerCount() > 1 ) ) {
- $dbw = wfGetDB( DB_MASTER );
- $row = $dbw->selectRow( 'text',
+ // Fallback to DB_MASTER in some cases if the row was not found
+ if ( !$row && $fallbackIndex !== null ) {
+ // Use FOR UPDATE if it was used to fetch this revision. This avoids missing the row
+ // due to REPEATABLE-READ. Also fallback to the master if READ_LATEST is provided.
+ $row = wfGetDB( $fallbackIndex )->selectRow(
+ 'text',
[ 'old_text', 'old_flags' ],
[ 'old_id' => $textId ],
__METHOD__,
- $forUpdate ? [ 'FOR UPDATE' ] : [] );
+ $fallbackOptions
+ );
}
if ( !$row ) {