includes/Storage/BlobStore.php

   1 <?php
   2 /**
   3  * Service for loading and storing data blobs.
   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  * @file
  21  */
  22
  23 namespace MediaWiki\Storage;
  24
  25 use StatusValue;
  26
  27 /**
  28  * Service for loading and storing data blobs.
  29  *
  30  * @note This was written to act as a drop-in replacement for the corresponding
  31  *       static methods in Revision.
  32  *
  33  * @since 1.31
  34  */
  35 interface BlobStore {
  36
  37         /**
  38          * Hint key for use with storeBlob, indicating the general role the block
  39          * takes in the application. For instance, it should be "page-content" if
  40          * the blob represents a Content object.
  41          */
  42         const DESIGNATION_HINT = 'designation';
  43
  44         /**
  45          * Hint key for use with storeBlob, indicating the page the blob is associated with.
  46          * This may be used for sharding.
  47          */
  48         const PAGE_HINT = 'page_id';
  49
  50         /**
  51          * Hint key for use with storeBlob, indicating the slot the blob is associated with.
  52          * May be relevant for reference counting.
  53          */
  54         const ROLE_HINT = 'role_name';
  55
  56         /**
  57          * Hint key for use with storeBlob, indicating the revision the blob is associated with.
  58          * This may be used for differential storage and reference counting.
  59          */
  60         const REVISION_HINT = 'rev_id';
  61
  62         /**
  63          * Hint key for use with storeBlob, indicating the parent revision of the revision
  64          * the blob is associated with. This may be used for differential storage.
  65          */
  66         const PARENT_HINT = 'rev_parent_id';
  67
  68         /**
  69          * Hint key for use with storeBlob, providing the SHA1 hash of the blob as passed to the
  70          * method. This can be used to avoid re-calculating the hash if it is needed by the BlobStore.
  71          */
  72         const SHA1_HINT = 'cont_sha1';
  73
  74         /**
  75          * Hint key for use with storeBlob, indicating the model of the content encoded in the
  76          * given blob. May be used to implement optimized storage for some well known models.
  77          */
  78         const MODEL_HINT = 'cont_model';
  79
  80         /**
  81          * Hint key for use with storeBlob, indicating the serialization format used to create
  82          * the blob, as a MIME type. May be used for optimized storage in the underlying database.
  83          */
  84         const FORMAT_HINT = 'cont_format';
  85
  86         /**
  87          * Retrieve a blob, given an address.
  88          *
  89          * MCR migration note: this replaces Revision::loadText
  90          *
  91          * @param string $blobAddress The blob address as returned by storeBlob(),
  92          *        such as "tt:12345" or "ex:DB://s16/456/9876".
  93          * @param int $queryFlags See IDBAccessObject.
  94          *
  95          * @throws BlobAccessException
  96          * @return string binary blob data
  97          */
  98         public function getBlob( $blobAddress, $queryFlags = 0 );
  99
 100         /**
 101          * A batched version of BlobStore::getBlob.
 102          *
 103          * @param string[] $blobAddresses An array of blob addresses.
 104          * @param int $queryFlags See IDBAccessObject.
 105          * @throws BlobAccessException
 106          * @return StatusValue A status with a map of blobAddress => binary blob data or null
 107          *         if fetching the blob has failed. Fetch failures errors are the
 108          *         warnings in the status object.
 109          * @since 1.34
 110          */
 111         public function getBlobBatch( $blobAddresses, $queryFlags = 0 );
 112
 113         /**
 114          * Stores an arbitrary blob of data and returns an address that can be used with
 115          * getBlob() to retrieve the same blob of data,
 116          *
 117          * @param string $data raw binary data
 118          * @param array $hints An array of hints. Implementations may use the hints to optimize storage.
 119          * All hints are optional, supported hints depend on the implementation. Hint names by
 120          * convention correspond to the names of fields in the database. Callers are encouraged to
 121          * provide the well known hints as defined by the XXX_HINT constants.
 122          *
 123          * @throws BlobAccessException
 124          * @return string an address that can be used with getBlob() to retrieve the data.
 125          */
 126         public function storeBlob( $data, $hints = [] );
 127
 128         /**
 129          * Check if the blob metadata or backing blob data store is read-only
 130          *
 131          * @return bool
 132          */
 133         public function isReadOnly();
 134 }