MongoDB::Database(3) User Contributed Perl Documentation MongoDB::Database(3)NAMEMongoDB::Database - A Mongo database
SYNOPSIS
The MongoDB::Database class accesses to a database.
# accesses the foo database
my $db = $connection->foo;
You can also access databases with the "get_database($name)" in
MongoDB::Connection method.
SEE ALSO
Core documentation on databases:
<http://dochub.mongodb.org/core/databases>.
ATTRIBUTES
name
The name of the database.
METHODS
collection_names
my @collections = $database->collection_names;
Returns the list of collections in this database.
get_collection ($name)
my $collection = $database->get_collection('foo');
Returns a MongoDB::Collection for the collection called $name within
this database.
get_gridfs ($prefix?)
my $grid = $database->get_gridfs;
Returns a MongoDB::GridFS for storing and retrieving files from the
database. Default prefix is "fs", making "$grid->files" "fs.files" and
"$grid->chunks" "fs.chunks".
See MongoDB::GridFS for more information.
drop
$database->drop;
Deletes the database.
last_error($options?)
my $err = $db->last_error({w => 2});
Finds out if the last database operation completed successfully. If
the last operation did not complete successfully, returns a hash
reference of information about the error that occured.
The optional $options parameter is a hash reference that can contain
any of the following:
w Guarantees that the previous operation will be replicated to "w"
servers before this command will return success. See
"MongoDB::Connection::w" for more information.
wtimeout
Milliseconds to wait for "w" copies of the data to be made. This
parameter should generally be specified, as the database will
otherwise wait forever if "w" copies cannot be made.
fsync
If true, the database will fsync to disk before returning.
"last_error" returns a hash with fields that vary, depending on what
the previous operation was and if it succeeded or failed. If the last
operation (before the "last_error" call) failed, either:
"err" will be set or
"errmsg" will be set and "ok" will be 0.
If "err" is "null" and "ok" is 1, the previous operation succeeded.
The fields in the hash returned can include (but are not limited to):
"ok"
This should almost be 1 (unless "last_error" itself failed).
"err"
If this field is non-null, an error occurred on the previous
operation. If this field is set, it will be a string describing the
error that occurred.
"code"
If a database error occurred, the relevant error code will be
passed back to the client.
"errmsg"
This field is set if something goes wrong with a database command.
It is coupled with "ok" being 0. For example, if "w" is set and
times out, "errmsg" will be set to "timed out waiting for slaves"
and "ok" will be 0. If this field is set, it will be a string
describing the error that occurred.
"n" If the last operation was an insert, an update or a remove, the
number of objects affected will be returned.
"wtimeout"
If the previous option timed out waiting for replication.
"waited"
How long the operation waited before timing out.
"wtime"
If "w" was set and the operation succeeded, how long it took to
replicate to "w" servers.
"upserted"
If an upsert occured, this field will contain the new record's
"_id" field. For upserts, either this field or "updatedExisting"
will be present (unless an error occurred).
"updatedExisting"
If an upsert updated an existing element, this field will be
"true". For upserts, either this field or "upserted" will be
present (unless an error occurred).
See "w" in MongoDB::Connection for more information.
run_command ($command)
my $result = $database->run_command({ some_command => 1 });
Runs a database command. Returns a string with the error message if the
command fails. Returns the result of the command (a hash reference) on
success. For a list of possible database commands, run:
my $commands = $db->run_command({listCommands : 1});
There are a few examples of database commands in the "DATABASE
COMMANDS" in MongoDB::Examples section.
See also core documentation on database commands:
<http://dochub.mongodb.org/core/commands>.
eval ($code, $args?)
my $result = $database->eval('function(x) { return "hello, "+x; }', ["world"]);
Evaluate a JavaScript expression on the Mongo server. The $code
argument can be a string or an instance of MongoDB::Code. The $args
are an optional array of arguments to be passed to the $code function.
"eval" is useful if you need to touch a lot of data lightly; in such a
scenario the network transfer of the data could be a bottleneck. The
$code argument must be a JavaScript function. $args is an array of
parameters that will be passed to the function. For more examples of
using eval see
http://www.mongodb.org/display/DOCS/Server-side+Code+Execution#Server-sideCodeExecution-Using{{db.eval%28%29}}
<http://www.mongodb.org/display/DOCS/Server-side+Code+Execution#Server-
sideCodeExecution-Using{{db.eval%28%29}}>.
AUTHOR
Kristina Chodorow <kristina@mongodb.org>
perl v5.14.2 2011-09-07 MongoDB::Database(3)
