The MongoGridFS class
(PECL mongo >=0.9.0)
简介
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"));
?>
Inter-Language Compatibility
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())));
?>
The MongoGridFS Family
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 $grid->chunks collection.
MongoGridFSFile objects contain a field file which contains any file metadata.
类摘要
NULL
;NULL
;$bytes
[, array $metadata = array()
[, array $options = array()
]] ) : mixed参见
- MongoDB core docs on » GridFS
- LightCube Solutions blog post on » saving user uploads
- LightCube Solutions blog post on » adding metadata to files
Table of Contents
- MongoGridFS::__construct — Creates new file collections
- MongoGridFS::delete — Remove a file and its chunks from the database
- MongoGridFS::drop — Drops the files and chunks collections
- MongoGridFS::find — Queries for files
- MongoGridFS::findOne — Returns a single file matching the criteria
- MongoGridFS::get — Retrieve a file from the database
- MongoGridFS::put — Stores a file in the database
- MongoGridFS::remove — Remove files and their chunks from the database
- MongoGridFS::storeBytes — Stores a string of bytes in the database
- MongoGridFS::storeFile — Stores a file in the database
- MongoGridFS::storeUpload — Stores an uploaded file in the database