includes/Storage/SqlBlobStore.php

   1 <?php
   2 /**
   3  * Service for storing and loading data blobs representing revision content.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * Attribution notice: when this file was created, much of its content was taken
  21  * from the Revision.php file as present in release 1.30. Refer to the history
  22  * of that file for original authorship.
  23  *
  24  * @file
  25  */
  26
  27 namespace MediaWiki\Storage;
  28
  29 use AppendIterator;
  30 use DBAccessObjectUtils;
  31 use IDBAccessObject;
  32 use IExpiringStore;
  33 use InvalidArgumentException;
  34 use Language;
  35 use MWException;
  36 use StatusValue;
  37 use WANObjectCache;
  38 use ExternalStoreAccess;
  39 use Wikimedia\Assert\Assert;
  40 use Wikimedia\Rdbms\IDatabase;
  41 use Wikimedia\Rdbms\ILoadBalancer;
  42
  43 /**
  44  * Service for storing and loading Content objects.
  45  *
  46  * @since 1.31
  47  *
  48  * @note This was written to act as a drop-in replacement for the corresponding
  49  *       static methods in Revision.
  50  */
  51 class SqlBlobStore implements IDBAccessObject, BlobStore {
  52
  53         // Note: the name has been taken unchanged from the Revision class.
  54         const TEXT_CACHE_GROUP = 'revisiontext:10';
  55
  56         /**
  57          * @var ILoadBalancer
  58          */
  59         private $dbLoadBalancer;
  60
  61         /**
  62          * @var ExternalStoreAccess
  63          */
  64         private $extStoreAccess;
  65
  66         /**
  67          * @var WANObjectCache
  68          */
  69         private $cache;
  70
  71         /**
  72          * @var string|bool DB domain ID of a wiki or false for the local one
  73          */
  74         private $dbDomain;
  75
  76         /**
  77          * @var int
  78          */
  79         private $cacheExpiry = 604800; // 7 days
  80
  81         /**
  82          * @var bool
  83          */
  84         private $compressBlobs = false;
  85
  86         /**
  87          * @var bool|string
  88          */
  89         private $legacyEncoding = false;
  90
  91         /**
  92          * @var Language|null
  93          */
  94         private $legacyEncodingConversionLang = null;
  95
  96         /**
  97          * @var boolean
  98          */
  99         private $useExternalStore = false;
 100
 101         /**
 102          * @param ILoadBalancer $dbLoadBalancer A load balancer for acquiring database connections
 103          * @param ExternalStoreAccess $extStoreAccess Access layer for external storage
 104          * @param WANObjectCache $cache A cache manager for caching blobs. This can be the local
 105          *        wiki's default instance even if $dbDomain refers to a different wiki, since
 106          *        makeGlobalKey() is used to construct a key that allows cached blobs from the
 107          *        same database to be re-used between wikis. For example, wiki A and wiki B will
 108          *        use the same cache keys for blobs fetched from wiki C, regardless of the
 109          *        wiki-specific default key space.
 110          * @param bool|string $dbDomain The ID of the target wiki database. Use false for the local wiki.
 111          */
 112         public function __construct(
 113                 ILoadBalancer $dbLoadBalancer,
 114                 ExternalStoreAccess $extStoreAccess,
 115                 WANObjectCache $cache,
 116                 $dbDomain = false
 117         ) {
 118                 $this->dbLoadBalancer = $dbLoadBalancer;
 119                 $this->extStoreAccess = $extStoreAccess;
 120                 $this->cache = $cache;
 121                 $this->dbDomain = $dbDomain;
 122         }
 123
 124         /**
 125          * @return int time for which blobs can be cached, in seconds
 126          */
 127         public function getCacheExpiry() {
 128                 return $this->cacheExpiry;
 129         }
 130
 131         /**
 132          * @param int $cacheExpiry time for which blobs can be cached, in seconds
 133          */
 134         public function setCacheExpiry( $cacheExpiry ) {
 135                 Assert::parameterType( 'integer', $cacheExpiry, '$cacheExpiry' );
 136
 137                 $this->cacheExpiry = $cacheExpiry;
 138         }
 139
 140         /**
 141          * @return bool whether blobs should be compressed for storage
 142          */
 143         public function getCompressBlobs() {
 144                 return $this->compressBlobs;
 145         }
 146
 147         /**
 148          * @param bool $compressBlobs whether blobs should be compressed for storage
 149          */
 150         public function setCompressBlobs( $compressBlobs ) {
 151                 $this->compressBlobs = $compressBlobs;
 152         }
 153
 154         /**
 155          * @return false|string The legacy encoding to assume for blobs that are not marked as utf8.
 156          *         False means handling of legacy encoding is disabled, and utf8 assumed.
 157          */
 158         public function getLegacyEncoding() {
 159                 return $this->legacyEncoding;
 160         }
 161
 162         /**
 163          * @return Language|null The locale to use when decoding from a legacy encoding, or null
 164          *         if handling of legacy encoding is disabled.
 165          */
 166         public function getLegacyEncodingConversionLang() {
 167                 return $this->legacyEncodingConversionLang;
 168         }
 169
 170         /**
 171          * @param string $legacyEncoding The legacy encoding to assume for blobs that are
 172          *        not marked as utf8.
 173          * @param Language $language The locale to use when decoding from a legacy encoding.
 174          */
 175         public function setLegacyEncoding( $legacyEncoding, Language $language ) {
 176                 Assert::parameterType( 'string', $legacyEncoding, '$legacyEncoding' );
 177
 178                 $this->legacyEncoding = $legacyEncoding;
 179                 $this->legacyEncodingConversionLang = $language;
 180         }
 181
 182         /**
 183          * @return bool Whether to use the ExternalStore mechanism for storing blobs.
 184          */
 185         public function getUseExternalStore() {
 186                 return $this->useExternalStore;
 187         }
 188
 189         /**
 190          * @param bool $useExternalStore Whether to use the ExternalStore mechanism for storing blobs.
 191          */
 192         public function setUseExternalStore( $useExternalStore ) {
 193                 Assert::parameterType( 'boolean', $useExternalStore, '$useExternalStore' );
 194
 195                 $this->useExternalStore = $useExternalStore;
 196         }
 197
 198         /**
 199          * @return ILoadBalancer
 200          */
 201         private function getDBLoadBalancer() {
 202                 return $this->dbLoadBalancer;
 203         }
 204
 205         /**
 206          * @param int $index A database index, like DB_MASTER or DB_REPLICA
 207          *
 208          * @return IDatabase
 209          */
 210         private function getDBConnection( $index ) {
 211                 $lb = $this->getDBLoadBalancer();
 212                 return $lb->getConnectionRef( $index, [], $this->dbDomain );
 213         }
 214
 215         /**
 216          * Stores an arbitrary blob of data and returns an address that can be used with
 217          * getBlob() to retrieve the same blob of data,
 218          *
 219          * @param string $data
 220          * @param array $hints An array of hints.
 221          *
 222          * @throws BlobAccessException
 223          * @return string an address that can be used with getBlob() to retrieve the data.
 224          */
 225         public function storeBlob( $data, $hints = [] ) {
 226                 try {
 227                         $flags = $this->compressData( $data );
 228
 229                         # Write to external storage if required
 230                         if ( $this->useExternalStore ) {
 231                                 // Store and get the URL
 232                                 $data = $this->extStoreAccess->insert( $data, [ 'domain' => $this->dbDomain ] );
 233                                 if ( !$data ) {
 234                                         throw new BlobAccessException( "Failed to store text to external storage" );
 235                                 }
 236                                 if ( $flags ) {
 237                                         $flags .= ',';
 238                                 }
 239                                 $flags .= 'external';
 240
 241                                 // TODO: we could also return an address for the external store directly here.
 242                                 // That would mean bypassing the text table entirely when the external store is
 243                                 // used. We'll need to assess expected fallout before doing that.
 244                         }
 245
 246                         $dbw = $this->getDBConnection( DB_MASTER );
 247
 248                         $old_id = $dbw->nextSequenceValue( 'text_old_id_seq' );
 249                         $dbw->insert(
 250                                 'text',
 251                                 [
 252                                         'old_id' => $old_id,
 253                                         'old_text' => $data,
 254                                         'old_flags' => $flags,
 255                                 ],
 256                                 __METHOD__
 257                         );
 258
 259                         $textId = $dbw->insertId();
 260
 261                         return self::makeAddressFromTextId( $textId );
 262                 } catch ( MWException $e ) {
 263                         throw new BlobAccessException( $e->getMessage(), 0, $e );
 264                 }
 265         }
 266
 267         /**
 268          * Retrieve a blob, given an address.
 269          * Currently hardcoded to the 'text' table storage engine.
 270          *
 271          * MCR migration note: this replaces Revision::loadText
 272          *
 273          * @param string $blobAddress
 274          * @param int $queryFlags
 275          *
 276          * @throws BlobAccessException
 277          * @return string
 278          */
 279         public function getBlob( $blobAddress, $queryFlags = 0 ) {
 280                 Assert::parameterType( 'string', $blobAddress, '$blobAddress' );
 281
 282                 $error = null;
 283                 $blob = $this->cache->getWithSetCallback(
 284                         $this->getCacheKey( $blobAddress ),
 285                         $this->getCacheTTL(),
 286                         function ( $unused, &$ttl, &$setOpts ) use ( $blobAddress, $queryFlags, &$error ) {
 287                                 // Ignore $setOpts; blobs are immutable and negatives are not cached
 288                                 list( $result, $errors ) = $this->fetchBlobs( [ $blobAddress ], $queryFlags );
 289                                 // No negative caching; negative hits on text rows may be due to corrupted replica DBs
 290                                 $error = $errors[$blobAddress] ?? null;
 291                                 return $result[$blobAddress];
 292                         },
 293                         [ 'pcGroup' => self::TEXT_CACHE_GROUP, 'pcTTL' => IExpiringStore::TTL_PROC_LONG ]
 294                 );
 295
 296                 if ( $error ) {
 297                         throw new BlobAccessException( $error );
 298                 }
 299
 300                 Assert::postcondition( is_string( $blob ), 'Blob must not be null' );
 301                 return $blob;
 302         }
 303
 304         /**
 305          * A batched version of BlobStore::getBlob.
 306          *
 307          * @param string[] $blobAddresses An array of blob addresses.
 308          * @param int $queryFlags See IDBAccessObject.
 309          * @throws BlobAccessException
 310          * @return StatusValue A status with a map of blobAddress => binary blob data or null
 311          *         if fetching the blob has failed. Fetch failures errors are the
 312          *         warnings in the status object.
 313          * @since 1.34
 314          */
 315         public function getBlobBatch( $blobAddresses, $queryFlags = 0 ) {
 316                 $errors = null;
 317                 $addressByCacheKey = $this->cache->makeMultiKeys(
 318                         $blobAddresses,
 319                         function ( $blobAddress ) {
 320                                 return $this->getCacheKey( $blobAddress );
 321                         }
 322                 );
 323                 $blobsByCacheKey = $this->cache->getMultiWithUnionSetCallback(
 324                         $addressByCacheKey,
 325                         $this->getCacheTTL(),
 326                         function ( array $blobAddresses, array &$ttls, array &$setOpts ) use ( $queryFlags, &$errors ) {
 327                                 // Ignore $setOpts; blobs are immutable and negatives are not cached
 328                                 list( $result, $errors ) = $this->fetchBlobs( $blobAddresses, $queryFlags );
 329                                 return $result;
 330                         },
 331                         [ 'pcGroup' => self::TEXT_CACHE_GROUP, 'pcTTL' => IExpiringStore::TTL_PROC_LONG ]
 332                 );
 333
 334                 // Remap back to incoming blob addresses. The return value of the
 335                 // WANObjectCache::getMultiWithUnionSetCallback is keyed on the internal
 336                 // keys from WANObjectCache::makeMultiKeys, so we need to remap them
 337                 // before returning to the client.
 338                 $blobsByAddress = [];
 339                 foreach ( $blobsByCacheKey as $cacheKey => $blob ) {
 340                         $blobsByAddress[ $addressByCacheKey[ $cacheKey ] ] = $blob !== false ? $blob : null;
 341                 }
 342
 343                 $result = StatusValue::newGood( $blobsByAddress );
 344                 if ( $errors ) {
 345                         foreach ( $errors as $error ) {
 346                                 $result->warning( 'internalerror', $error );
 347                         }
 348                 }
 349                 return $result;
 350         }
 351
 352         /**
 353          * MCR migration note: this corresponds to Revision::fetchText
 354          *
 355          * @param string[] $blobAddresses
 356          * @param int $queryFlags
 357          *
 358          * @throws BlobAccessException
 359          * @return array [ $result, $errors ] A map of blob addresses to successfully fetched blobs
 360          *         or false if fetch failed, plus and array of errors
 361          */
 362         private function fetchBlobs( $blobAddresses, $queryFlags ) {
 363                 $textIdToBlobAddress = [];
 364                 $result = [];
 365                 $errors = [];
 366                 foreach ( $blobAddresses as $blobAddress ) {
 367                         list( $schema, $id ) = self::splitBlobAddress( $blobAddress );
 368                         //TODO: MCR: also support 'ex' schema with ExternalStore URLs, plus flags encoded in the URL!
 369                         if ( $schema === 'tt' ) {
 370                                 $textId = intval( $id );
 371                                 $textIdToBlobAddress[$textId] = $blobAddress;
 372                         } else {
 373                                 $errors[$blobAddress] = "Unknown blob address schema: $schema";
 374                                 $result[$blobAddress] = false;
 375                                 continue;
 376                         }
 377
 378                         if ( !$textId || $id !== (string)$textId ) {
 379                                 $errors[$blobAddress] = "Bad blob address: $blobAddress";
 380                                 $result[$blobAddress] = false;
 381                         }
 382                 }
 383
 384                 $textIds = array_keys( $textIdToBlobAddress );
 385                 if ( !$textIds ) {
 386                         return [ $result, $errors ];
 387                 }
 388                 // Callers doing updates will pass in READ_LATEST as usual. Since the text/blob tables
 389                 // do not normally get rows changed around, set READ_LATEST_IMMUTABLE in those cases.
 390                 $queryFlags |= DBAccessObjectUtils::hasFlags( $queryFlags, self::READ_LATEST )
 391                         ? self::READ_LATEST_IMMUTABLE
 392                         : 0;
 393                 list( $index, $options, $fallbackIndex, $fallbackOptions ) =
 394                         DBAccessObjectUtils::getDBOptions( $queryFlags );
 395                 // Text data is immutable; check replica DBs first.
 396                 $dbConnection = $this->getDBConnection( $index );
 397                 $rows = $dbConnection->select(
 398                         'text',
 399                         [ 'old_id', 'old_text', 'old_flags' ],
 400                         [ 'old_id' => $textIds ],
 401                         __METHOD__,
 402                         $options
 403                 );
 404
 405                 // Fallback to DB_MASTER in some cases if not all the rows were found, using the appropriate
 406                 // options, such as FOR UPDATE to avoid missing rows due to REPEATABLE-READ.
 407                 if ( $dbConnection->numRows( $rows ) !== count( $textIds ) && $fallbackIndex !== null ) {
 408                         $fetchedTextIds = [];
 409                         foreach ( $rows as $row ) {
 410                                 $fetchedTextIds[] = $row->old_id;
 411                         }
 412                         $missingTextIds = array_diff( $textIds, $fetchedTextIds );
 413                         $dbConnection = $this->getDBConnection( $fallbackIndex );
 414                         $rowsFromFallback = $dbConnection->select(
 415                                 'text',
 416                                 [ 'old_id', 'old_text', 'old_flags' ],
 417                                 [ 'old_id' => $missingTextIds ],
 418                                 __METHOD__,
 419                                 $fallbackOptions
 420                         );
 421                         $appendIterator = new AppendIterator();
 422                         $appendIterator->append( $rows );
 423                         $appendIterator->append( $rowsFromFallback );
 424                         $rows = $appendIterator;
 425                 }
 426
 427                 foreach ( $rows as $row ) {
 428                         $blobAddress = $textIdToBlobAddress[$row->old_id];
 429                         $blob = $this->expandBlob( $row->old_text, $row->old_flags, $blobAddress );
 430                         if ( $blob === false ) {
 431                                 $errors[$blobAddress] = "Bad data in text row {$row->old_id}.";
 432                         }
 433                         $result[$blobAddress] = $blob;
 434                 }
 435
 436                 // If we're still missing some of the rows, set errors for missing blobs.
 437                 if ( count( $result ) !== count( $blobAddresses ) ) {
 438                         foreach ( $blobAddresses as $blobAddress ) {
 439                                 if ( !isset( $result[$blobAddress ] ) ) {
 440                                         $errors[$blobAddress] = "Unable to fetch blob at $blobAddress";
 441                                         $result[$blobAddress] = false;
 442                                 }
 443                         }
 444                 }
 445                 return [ $result, $errors ];
 446         }
 447
 448         /**
 449          * Get a cache key for a given Blob address.
 450          *
 451          * The cache key is constructed in a way that allows cached blobs from the same database
 452          * to be re-used between wikis. For example, wiki A and wiki B will use the same cache keys
 453          * for blobs fetched from wiki C.
 454          *
 455          * @param string $blobAddress
 456          * @return string
 457          */
 458         private function getCacheKey( $blobAddress ) {
 459                 return $this->cache->makeGlobalKey(
 460                         'SqlBlobStore-blob',
 461                         $this->dbLoadBalancer->resolveDomainID( $this->dbDomain ),
 462                         $blobAddress
 463                 );
 464         }
 465
 466         /**
 467          * Expand a raw data blob according to the flags given.
 468          *
 469          * MCR migration note: this replaces Revision::getRevisionText
 470          *
 471          * @note direct use is deprecated, use getBlob() or SlotRecord::getContent() instead.
 472          * @todo make this private, there should be no need to use this method outside this class.
 473          *
 474          * @param string $raw The raw blob data, to be processed according to $flags.
 475          *        May be the blob itself, or the blob compressed, or just the address
 476          *        of the actual blob, depending on $flags.
 477          * @param string|string[] $flags Blob flags, such as 'external' or 'gzip'.
 478          *   Note that not including 'utf-8' in $flags will cause the data to be decoded
 479          *   according to the legacy encoding specified via setLegacyEncoding.
 480          * @param string|null $cacheKey A blob address for use in the cache key. If not given,
 481          *   caching is disabled.
 482          *
 483          * @return false|string The expanded blob or false on failure
 484          */
 485         public function expandBlob( $raw, $flags, $cacheKey = null ) {
 486                 if ( is_string( $flags ) ) {
 487                         $flags = explode( ',', $flags );
 488                 }
 489
 490                 // Use external methods for external objects, text in table is URL-only then
 491                 if ( in_array( 'external', $flags ) ) {
 492                         $url = $raw;
 493                         $parts = explode( '://', $url, 2 );
 494                         if ( count( $parts ) == 1 || $parts[1] == '' ) {
 495                                 return false;
 496                         }
 497
 498                         if ( $cacheKey ) {
 499                                 // The cached value should be decompressed, so handle that and return here.
 500                                 return $this->cache->getWithSetCallback(
 501                                         $this->getCacheKey( $cacheKey ),
 502                                         $this->getCacheTTL(),
 503                                         function () use ( $url, $flags ) {
 504                                                 // Ignore $setOpts; blobs are immutable and negatives are not cached
 505                                                 $blob = $this->extStoreAccess
 506                                                         ->fetchFromURL( $url, [ 'domain' => $this->dbDomain ] );
 507
 508                                                 return $blob === false ? false : $this->decompressData( $blob, $flags );
 509                                         },
 510                                         [ 'pcGroup' => self::TEXT_CACHE_GROUP, 'pcTTL' => WANObjectCache::TTL_PROC_LONG ]
 511                                 );
 512                         } else {
 513                                 $blob = $this->extStoreAccess->fetchFromURL( $url, [ 'domain' => $this->dbDomain ] );
 514                                 return $blob === false ? false : $this->decompressData( $blob, $flags );
 515                         }
 516                 } else {
 517                         return $this->decompressData( $raw, $flags );
 518                 }
 519         }
 520
 521         /**
 522          * If $wgCompressRevisions is enabled, we will compress data.
 523          * The input string is modified in place.
 524          * Return value is the flags field: contains 'gzip' if the
 525          * data is compressed, and 'utf-8' if we're saving in UTF-8
 526          * mode.
 527          *
 528          * MCR migration note: this replaces Revision::compressRevisionText
 529          *
 530          * @note direct use is deprecated!
 531          * @todo make this private, there should be no need to use this method outside this class.
 532          *
 533          * @param mixed &$blob Reference to a text
 534          *
 535          * @return string
 536          */
 537         public function compressData( &$blob ) {
 538                 $blobFlags = [];
 539
 540                 // Revisions not marked as UTF-8 will have legacy decoding applied by decompressData().
 541                 // XXX: if $this->legacyEncoding is not set, we could skip this. That would however be
 542                 // risky, since $this->legacyEncoding being set in the future would lead to data corruption.
 543                 $blobFlags[] = 'utf-8';
 544
 545                 if ( $this->compressBlobs ) {
 546                         if ( function_exists( 'gzdeflate' ) ) {
 547                                 $deflated = gzdeflate( $blob );
 548
 549                                 if ( $deflated === false ) {
 550                                         wfLogWarning( __METHOD__ . ': gzdeflate() failed' );
 551                                 } else {
 552                                         $blob = $deflated;
 553                                         $blobFlags[] = 'gzip';
 554                                 }
 555                         } else {
 556                                 wfDebug( __METHOD__ . " -- no zlib support, not compressing\n" );
 557                         }
 558                 }
 559                 return implode( ',', $blobFlags );
 560         }
 561
 562         /**
 563          * Re-converts revision text according to its flags.
 564          *
 565          * MCR migration note: this replaces Revision::decompressRevisionText
 566          *
 567          * @note direct use is deprecated, use getBlob() or SlotRecord::getContent() instead.
 568          * @todo make this private, there should be no need to use this method outside this class.
 569          *
 570          * @param string $blob Blob in compressed/encoded form.
 571          * @param array $blobFlags Compression flags, such as 'gzip'.
 572          *   Note that not including 'utf-8' in $blobFlags will cause the data to be decoded
 573          *   according to the legacy encoding specified via setLegacyEncoding.
 574          *
 575          * @return string|bool Decompressed text, or false on failure
 576          */
 577         public function decompressData( $blob, array $blobFlags ) {
 578                 // Revision::decompressRevisionText accepted false here, so defend against that
 579                 Assert::parameterType( 'string', $blob, '$blob' );
 580
 581                 if ( in_array( 'error', $blobFlags ) ) {
 582                         // Error row, return false
 583                         return false;
 584                 }
 585
 586                 if ( in_array( 'gzip', $blobFlags ) ) {
 587                         # Deal with optional compression of archived pages.
 588                         # This can be done periodically via maintenance/compressOld.php, and
 589                         # as pages are saved if $wgCompressRevisions is set.
 590                         $blob = gzinflate( $blob );
 591
 592                         if ( $blob === false ) {
 593                                 wfWarn( __METHOD__ . ': gzinflate() failed' );
 594                                 return false;
 595                         }
 596                 }
 597
 598                 if ( in_array( 'object', $blobFlags ) ) {
 599                         # Generic compressed storage
 600                         $obj = unserialize( $blob );
 601                         if ( !is_object( $obj ) ) {
 602                                 // Invalid object
 603                                 return false;
 604                         }
 605                         $blob = $obj->getText();
 606                 }
 607
 608                 // Needed to support old revisions left over from from the 1.4 / 1.5 migration.
 609                 if ( $blob !== false && $this->legacyEncoding && $this->legacyEncodingConversionLang
 610                         && !in_array( 'utf-8', $blobFlags ) && !in_array( 'utf8', $blobFlags )
 611                 ) {
 612                         # Old revisions kept around in a legacy encoding?
 613                         # Upconvert on demand.
 614                         # ("utf8" checked for compatibility with some broken
 615                         #  conversion scripts 2008-12-30)
 616                         $blob = $this->legacyEncodingConversionLang->iconv( $this->legacyEncoding, 'UTF-8', $blob );
 617                 }
 618
 619                 return $blob;
 620         }
 621
 622         /**
 623          * Get the text cache TTL
 624          *
 625          * MCR migration note: this replaces Revision::getCacheTTL
 626          *
 627          * @return int
 628          */
 629         private function getCacheTTL() {
 630                 if ( $this->cache->getQoS( WANObjectCache::ATTR_EMULATION )
 631                                 <= WANObjectCache::QOS_EMULATION_SQL
 632                 ) {
 633                         // Do not cache RDBMs blobs in...the RDBMs store
 634                         $ttl = WANObjectCache::TTL_UNCACHEABLE;
 635                 } else {
 636                         $ttl = $this->cacheExpiry ?: WANObjectCache::TTL_UNCACHEABLE;
 637                 }
 638
 639                 return $ttl;
 640         }
 641
 642         /**
 643          * Returns an ID corresponding to the old_id field in the text table, corresponding
 644          * to the given $address.
 645          *
 646          * Currently, $address must start with 'tt:' followed by a decimal integer representing
 647          * the old_id; if $address does not start with 'tt:', null is returned. However,
 648          * the implementation may change to insert rows into the text table on the fly.
 649          * This implies that this method cannot be static.
 650          *
 651          * @note This method exists for use with the text table based storage schema.
 652          * It should not be assumed that is will function with all future kinds of content addresses.
 653          *
 654          * @deprecated since 1.31, so don't assume that all blob addresses refer to a row in the text
 655          * table. This method should become private once the relevant refactoring in WikiPage is
 656          * complete.
 657          *
 658          * @param string $address
 659          *
 660          * @return int|null
 661          */
 662         public function getTextIdFromAddress( $address ) {
 663                 list( $schema, $id, ) = self::splitBlobAddress( $address );
 664
 665                 if ( $schema !== 'tt' ) {
 666                         return null;
 667                 }
 668
 669                 $textId = intval( $id );
 670
 671                 if ( !$textId || $id !== (string)$textId ) {
 672                         throw new InvalidArgumentException( "Malformed text_id: $id" );
 673                 }
 674
 675                 return $textId;
 676         }
 677
 678         /**
 679          * Returns an address referring to content stored in the text table row with the given ID.
 680          * The address schema for blobs stored in the text table is "tt:" followed by an integer
 681          * that corresponds to a value of the old_id field.
 682          *
 683          * @deprecated since 1.31. This method should become private once the relevant refactoring
 684          * in WikiPage is complete.
 685          *
 686          * @param int $id
 687          *
 688          * @return string
 689          */
 690         public static function makeAddressFromTextId( $id ) {
 691                 return 'tt:' . $id;
 692         }
 693
 694         /**
 695          * Splits a blob address into three parts: the schema, the ID, and parameters/flags.
 696          *
 697          * @since 1.33
 698          *
 699          * @param string $address
 700          *
 701          * @throws InvalidArgumentException
 702          * @return array [ $schema, $id, $parameters ], with $parameters being an assoc array.
 703          */
 704         public static function splitBlobAddress( $address ) {
 705                 if ( !preg_match( '/^(\w+):(\w+)(\?(.*))?$/', $address, $m ) ) {
 706                         throw new InvalidArgumentException( "Bad blob address: $address" );
 707                 }
 708
 709                 $schema = strtolower( $m[1] );
 710                 $id = $m[2];
 711                 $parameters = isset( $m[4] ) ? wfCgiToArray( $m[4] ) : [];
 712
 713                 return [ $schema, $id, $parameters ];
 714         }
 715
 716         public function isReadOnly() {
 717                 if ( $this->useExternalStore && $this->extStoreAccess->isReadOnly() ) {
 718                         return true;
 719                 }
 720
 721                 return ( $this->getDBLoadBalancer()->getReadOnlyReason() !== false );
 722         }
 723 }