Mongo findAndModify

HERE
Implementing queues is a good use case for findAndModify


Which of these statements are true?

findAndModify is atomic.Update operations which update a single document are atomic.Usually, update is faster than findAndModify.

{
  findAndModify: <string>,
  query: <document>,
  sort: <document>,
  remove: <boolean>,
  update: <document>,
  new: <boolean>,
  fields: <document>,
  upsert: <boolean>
}

Read More..

Mongo M101P MongoDB for Developers week 3

Handling blobs (4 min)

GRIDFS
documents limited to 16MB in mongodb
breaks up large files into chunks and store them into a collection and meta data into another
By default GridFS limits chunk size to 256k
GridFS uses two collections to store files. One collection stores the file chunks, and the other stores file metadata.
collection
videos.chunks
videos.files
videos_meta?

When to denormalize (2 min)

Trees (2.5 min)

Benefits of embedding (2 min)

PERFORMANCE!

Multikeys (4 min)

Many to many relations (5 min)

One to many relations (5 min)

One to one relations (4 min)

Living without transactions (4 min)

Living without constraints (3 min)

Alternative schema for Blog (3 min)

Mongo design for Blog (4.5 min)

Relational normalization (5 min)

relational strives for 3rd normal form
denormalized

Goals of Normalization:

• frees database of modification anomalies (recall Andrews email example)
• minimize redesign when extending
• avoid any bias toward a particular access pattern (NOT A MONGO CONCERN)

"When you are not biased toward a particular access pattern you are equally bad at all of them"...Andrew Erlichson

Mongodb schema design (3 min)


mongo does not join in journal
joins are hard to scale
think about what data you want to use together
mongo has no constraints
atomic operations on documents

Quiz: MongoDB Schema Design

Whats the single most important factor in designing your application schema within MongoDB?

Making the design extensible.Making it easy to read by a human.Matching the data access patterns of your application.Keeping the data in third normal form.

Read More..

Mongo dba week 7 security backups

Additional Resources (2.5 min)

• Docs - mongodb.org
• Driver docs - 
• Bug database / feature request database [JIRA]
• Support forums (in Google Groups) - mongodb-user
• IRC - channel: freenode.net/#mongodb
• Source code on github
• Blog
• Twitter (@mongodb)
• Mongo Meetup Groups (MMUGs) - look on meetup.com

Hardware Tips (7.5 min)

Additional Features (4.5 min)

Geospatial Indexes (5 min)

location
latitude and longitude things
built on top of b-tree structures
uses variation of geo-hash codes

Data Recovery with MMS (4 min)

Quiz: Data Recovery with MMS Backup

You rack up $3.50 in MMS charges from a small backup restoration. What are your out-of-pocket costs?

-$1.50$0.00$1.50$3.50$5.00

Installing MMS Backup (3.5 min)

Introduction to MMS Backup ( min)

Backup Strategies (3 min)

Quiz: Backup Strategies

Which are true statements?

You can copy Mongo datafiles while a mongod is running.Its always safe to do a true snapshot of the data volume while mongod is running.mongoexport has the ability to directly access MongoDB datafiles in addition to connecting to a MongoDB cluster or server via the network.

Backups (12 min)

Intra-cluster Security (4 min)

Security and Clients (6.5 min)

--auth : runs it in a security mode.
to authenticate:
NOTE: users are added per-database
db.addUser(...) - system.users (which is used to create credentials in mongodb)
db.addUser( { user: "", pwd: "", roles: [] } ) - 2.4+
db.auth(username,password) - to authenticate in the shell
Types of users:
admin users - created in the admin database.  has privileges across all databases
regular users - access a specific database, read/write or read only.

Start by adding an administrative user:

> use admin

switched to db admin

> db.addUser("the_admin", "testpassword" )

{

"user" : "the_admin",

"readOnly" : false,

"pwd" : "8b7c802b3626405fd30fa921fcf41cf9",

"_id" : ObjectId("52851114c2e7840b9b05b49f")

}

> db

admin

> show collections

system.indexes

system.users

> db.system.users.find()

{ "_id" : ObjectId("52851114c2e7840b9b05b49f"), "user" : "the_admin", "readOnly" : false, "pwd" : "8b7c802b3626405fd30fa921fcf41cf9" }

passwords are hashed (not stored in plain text [i.e. a message digest])

Once the admin user has been added to the admin database, the rule that you can connect from the localhost no longer applies.  Meaning that we will have to authenticate or it wont let us in (even if we are on localhost).

> show dbs

Thu Nov 14 11:07:59.449 JavaScript execution failed: listDatabases failed:{ "ok" : 0, "errmsg" : "unauthorized" } at src/mongo/shell/mongo.js:L46

> // now we authenticate to do useful things

> db.auth("the_admin", "testpassword" )

1

> show dbs

admin 0.0625GB

local 0.03125GB

test (empty)

Quiz: Security and Clients

Which are true?

You can give a user read-only access to one database and write access to another database.The users password is sent over the network unencrypted.The users password is stored on disk unencrypted.

Security (5 min)

Introduction ( min)

Read More..