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이 문서에서는 PHP 중국어 웹사이트 매뉴얼 풀어 주다
(PECL mongo >=0.9.0)
Utilities for storing and retrieving files from the database.
GridFS is a storage specification all supported drivers implement. Basically, it defines two collections: files, for file metadata, and chunks, for file content. If the file is large, it will automatically be split into smaller chunks and each chunk will be saved as a document in the chunks collection.
Each document in the files collection contains the filename, upload date, and md5 hash. It also contains a unique _id field, which can be used to query the chunks collection for the file's content. Each document in the chunks collection contains a chunk of binary data, a files_id field that matches its file's _id, and the position of this chunk in the overall file.
For example, the files document is something like:
<?php
array( "_id" => 123456789 , "filename" => "foo.txt" , "chunkSize" => 3 , "length" => 12 );
?>
<?php
array( "files_id" => 123456789 , "n" => 0 , "data" => new MongoBinData ( "abc" ));
array( "files_id" => 123456789 , "n" => 1 , "data" => new MongoBinData ( "def" ));
array( "files_id" => 123456789 , "n" => 2 , "data" => new MongoBinData ( "ghi" ));
array( "files_id" => 123456789 , "n" => 3 , "data" => new MongoBinData ( "jkl" ));
?>
You should be able to use any files created by MongoGridFS with any other drivers, and vice versa. However, some drivers expect that all metadata associated with a file be in a "metadata" field. If you're going to be using other languages, it's a good idea to wrap info you might want them to see in a "metadata" field. For example, instead of:
<?php
$grid -> storeFile ( "somefile.txt" , array( "date" => new MongoDate ()));
?>
use something like:
<?php
$grid -> storeFile ( "somefile.txt" , array( "metadata" => array( "date" => new MongoDate ())));
?>
MongoGridFS represents the files and chunks collections. MongoGridFS extends MongoCollection, and an instance of MongoGridFS has access to all of MongoCollection methods, which act on the files collection:
<?php
$grid = $db -> getGridFS ();
$grid -> update (array( "filename" => "foo" ), $newObj ); // update on the files collection
?>
Another example of manipulating metadata:
<?php
// save a file
$id = $grid -> storeFile ( "game.tgz" );
$game = $grid -> findOne ();
// add a downloads counter
$game -> file [ 'downloads' ] = 0 ;
$grid -> save ( $game -> file );
// increment the counter
$grid -> update (array( "_id" => $id ), array( '$inc' => array( "downloads" => 1 )));
?>
You can also access the chunks collection from an instance of MongoGridFS:
<?php
$chunks = $grid -> chunks ; // $chunks is a normal MongoCollection
$chunks -> insert (array( "x" => 4 ));
?>
There are some methods for MongoGridFS with the same name as MongoCollection methods, that behave slightly differently. For example, MongoGridFS::remove() will remove any objects that match the criteria from the files collection and their content from the chunks collection.
To store something new in GridFS, there are a couple options. If you have a filename, you can say:
<?php
$grid -> storeFile ( $filename , array( "whatever" => "metadata" , "you" => "want" ));
?>
If you have a string of bytes that isn't a file, you can also store that using MongoGridFS::storeBytes() :
<?php
$grid -> storeBytes ( $bytes , array( "whatever" => "metadata" , "you" => "want" ));
?>
Querying a MongoGridFS collection returns a MongoGridFSCursor, which behaves like a normal MongoCursor except that it returns MongoGridFSFiles instead of associative arrays.
MongoGridFSFiles can be written back to disc using MongoGridFSFile::write() or retrieved in memory using MongoGridFSFile::getBytes() . There is currently no method that automatically streams chunks, but it would be fairly easy to write by querying the $grid->chunks collection.
MongoGridFSFile objects contain a field file which contains any file metadata.
NULL
;NULL
;NULL
;$db
[, string $prefix
= "fs"
[, mixed $chunks
= "fs"
]] )$id
)$query
= array()
[, array $fields
= array()
]] )$query
= array()
[, mixed $fields
= array()
]] )$id
)$filename
[, array $metadata
= array()
[, array $options
= array()
]] )$criteria
= array()
[, array $options
= array()
]] )$bytes
[, array $metadata
= array()
[, array $options
= array()
]] )$filename
[, array $metadata
= array()
[, array $options
= array()
]] )$name
[, array $metadata
] )