Notes on MongoDB / Quickstart Guide to MongoDB

• database holds collections
• collection holds documents
• document is a set of fields
• field is a key-value pair
• key is a name
• value is:
  • basic type
  • a document
  • or an array of values

$bson = bson_encode(null);
$bson = bson_encode(array('a' => 10));

	> use mydb

switched to db mydb

	> j = {name: 'mongo'}
	> db.things.save(j);
	> db.things.find();

	> for(var i=1;i<=20;i++) db.things.save({x:4, j:i});
	> db.things.find();

c = db.things.find();
	> while (c.hasNext()) printjson(c.next());
	> db.things.find().foreach(printjson);

  > var c = db.things.find()
  > printjson(c[4]);

will show the 5th record, not right because it will load all the results unto 4 in the memory which can have scalability issues

> db.things.find().toArray();

select * from things where name = "mongo"
> db.things.find({name: 'mongo'}).forEach(printjson);
select * from things where x = 4;
> db.things.find({x:4}).forEach(printjson);
NOTE: that the _id field is always returned

	db.things.find({x:4}), {j:true}.foreach(printjson);
> findOne() - syntactic sugar
	>printjson(db.things.findOne({name: 'mongo'});
this is the same as
	>find({name: 'mongo'}).limit(1);
>printjson
function(x) {
	print(tojson(x));
}

select * from users where age=33 order by name
db.users.find({age: 33}).sort({name: true});

select * from users where age>33
db.users.find({'age': {$gt: 33}})
or $lt

select * from users where name like '%joe%';
db.users.find({name:/Joe/});
"Joe%" = {name:/^Joe/};
$lt = less than , $lte = less than equal to

sort order desc = .sort({name: -1});

create index myindexname on users(name);
db.users.ensureIndex({name: true});

create index myindex on users(name, ts desc)
db.users.ensureIndex({name:1, ts:-1});

select * from users where a=1 or b = 2
db.users.find({$or: [{a:1}, {b:2}]});

explain select * from users where z=2;
db.users.find({z:2}).explain();

select distinct last_name from users;
db.users.disctinct('last_name');

select count(*) from users;
db.users.count();

select count(age) from users;
db.users.find(age: {$exists: true}).count();

db.$cmd.findOne({<commandname>: <value>[, options]});
the shell provides a helper function for this:
db.runCommand({<commandname>: <value>[, options]);

for example to check our database current’ profile level eating
privileged commands:

> use admin
> db.runCommand('shutdown');

getting help info for a command

> db.commandHelp('datasize');

// copy the entire database from one name to one server
db.copyDatabase(<from-db>, <to-db>, <from-hostname>);

> use admin
> db.runCommand({sync: true, lock: 1});
unlock command:
db.$cmd.sys.unlock.findOne();

while the database can be read while locked for snapshoting, if a write is attempted, this will block readers due to the database’s use of read/write lock. (issues 1423);

> use test
> db.mycollection.ensureIndex(<keypattern>);
// same as
> db.system.indexes.insert({name: 'name', ns: 'namespaceToIndex', key: <keypatter>});

> db.system.indexes.find({ns: 'test.foo'});

db.mycollection.dropIndex(<name_or_pattern>);
db.mycollection.dropIndexes(); <-- drops all the indexes
e.g.
t.dropIndex({name: true});

db.$cmd.findOne({getlasterror:1});
or
db.runCommand('getlaterror');
or helper
db.getLastError();

> use comedy
> db.cartoon.validate();

returns stats about the collection along with the number of records etc

• system.namespcaes list all namespaces
• system.indexes lists all indexes
• system.profile stores database profiling information.
• system.users lists users who may access the database
• local.sources stores replica slave configuration data and state.
• information on the structure of a stored object is stored within the object itself.