Grid FS

Under development.

Methods:

• find_one
• find
• remove
• get
• insert
• new
• read
• write
• flush
• update_md5

Grid FS Object

:find_one

Parameters

Name	Description	Default	Required
fields	Unknown usage	?	Yes

Returns

A gridfs file object.

local gridfs_file = gridfs:find_one( fields )

:find

Parameters

Name	Description	Default	Required
fields	Unknown usage	?	Yes

Returns

A list of gridfs file objects.

local gridfs_files = gridfs:find( fields )
for _, file in ipairs( gridfs_files ) do
  print( file._id )
end

:remove

Parameters

Name	Description	Default	Required
fields	Unknown usage	?	Yes
singleRemove	Remove only the first result	0	No
safe	Issues a cmd getlasterror	0	No

Returns

Number of files deleted, or nil with error message

local n, err = gridfs:remove(fields, singleRemove, safe)

:get

Writes the first matching file to file_handle. This API will malloc a buffer in file size in memory.

Parameters

Name	Description	Default	Required
file_handle	An open file handle	none	Yes
fields	Fields to search for	none	Yes

Returns

On success returns True, otherwise False.

local bool = gridfs:get(file_handle, fields)

:insert

Insert a Grid FS file object.

Parameters

Name	Description	Default	Required
file_handle	A file handle returned from io.open	none	Yes
meta	A file metatable (see below)	meta.filename	No
safe	Issues a cmd getlasterror	0	No

Meta

The meta table can contain any additional information related to the file.

• _id
• filename
• chunkSize
• contentType
• aliases
• metadata (user data)

Returns

On success 0, or nil with error message.

local file_handle = io.open('some/file/path')
local n, err = gridfs:insert(file_handle, meta, safe)

:new

Creates a new Grid FS object.

Parameters

Name	Description	Default	Required
meta	A file metatable (see below)	meta.filename	Yes

Meta

The meta table can contain any additional information related to the file.

• _id
• filename
• chunkSize
• contentType
• aliases
• metadata (user data)

Returns

A gridfs file object, or nil with error message

local gridfs_file, err = gridfs:new(meta)

Grid FS File Object

:read

Read a file.

Parameters

Name	Description	Default	Required
size	The number of bytes to read	none	Yes
offset	Position to start the read	0	No

Returns

Number of bytes read, or nil with error message.

local n, err = gridfs_file:read(size, offset)

:write

Write a file.

Parameters

Name	Description	Default	Required
buf	File buffer?	none	Yes
offset	Position to start the write	0	No
size	The number of bytes to be written	none	Yes

Returns

Returns number of bytes written, or nil with error message.

local n, err = gridfs_file:write(buf, offset, size)

:flush

Flushes cached data in memory to the database. Should always be called at the end of a file write.

Parameters

None

Returns

Nothing

gridfs_file:flush()

:update_md5

Hashes the file content and updates the md5 in file collection.

Parameters

None

Returns

True on success, or False and error message

local bool, err = gridfs_file:update_md5()