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  1. NoSQL DBs

  2. What are the positives of relational DBs?

  3. Relational Positives • Historical positives of RDBMS: • Can represent relationships in data • Easy to understand relational model/SQL • Disk-oriented storage • Indexing structures • Consistent values in DB - transactions

  4. What are the negatives of relational DBs?

  5. Relational Negatives • RDBS strict, can be complex • Want more freedom, simplicity • RDBS limited in throughput • Want higher throughput • Must scale up (expensive servers) • Want to scale out (wide – cheap servers) • Overhead of object to relational mapping • Want to store data as is • Cannot always partition/distribute from single DB server • Want to distribute data • RDBS providers were slow to move to the cloud • Everyone wants to use the cloud • THE JOIN!!

  6. DBs today • Things have changed • Data no longer just in relational DBs • Different constraints on information • For example: • Placing items in shopping carts • Searching for answers in Wikipedia • Retrieving Web pages • Face book info • Large amounts of data!!!

  7. SQL NOT Good For: • Text • Data warehouses • Stream processing • Scientific and intelligence databases • Interactive transactions • Direct SQL interfaces are rare • Big Data ??!!

  8. Data Today • Different types of data: • Structured, semi-structured, unstructured • Structured - Info in databases • Data organized into chunks, similar entities grouped together • Descriptions for entities in groups – same format, length, etc.

  9. Data Today • Semi-structured – data has certain structure, but not all items identical • Similar entities grouped together – may have different attributes • Schema info may be mixed in with data values • Self-describing data, e.g. XML • May be displayed as a graph

  10. Data Today • Unstructured data • Data can be of any type, may have no format or sequence • cannot be represented by any type of schema • Web pages in HTML • Video, sound, images

  11. Characteristics of Big Data • Unstructured but some is semi-structured • Smartphones broadcasting location • Chips in cars diagnostic tests (1000s per sec) • Cameras recording public/private spaces • RFID tags read at as travel through supply-chain • Heterogeneous • Grows at a fast pace • Diverse • Not formally modeled • Data is valuable (always?) • Standard databases and data warehouses cannot capture diversity and heterogeneity • Cannot achieve satisfactory performance

  12. How to deal with such data • NoSQL – do not use a relational structure • MapReduce – from Google • NoSQL – do not use a relational structure • NoSQL used to stand for NO to SQL 1998 • but now it is Not Only SQL 2009

  13. NoSQL “NoSQL is not about any one feature of any of the projects. NoSQL is not about scaling, NoSQL is not about performance, NoSQL is not about hating SQL, NoSQL is not about ease of use, …, NoSQL is not about is not about throughput, NoSQL is not about about speed, …, NoSQL is not about open standards, NoSQL is not about Open Source and NoSQL is most likely not about whatever else you want NoSQL to be about. NoSQL is about choice.” Lehnardt of CouchDB

  14. Types of NoSQLDBs • Classification • Key-value stores (Dynamo, Voldemort) • Document stores (MongoDB, CouchDB, SimpleDB) • Column stores (BigTable, Hbase, Cassandra, CARE) • Graph-based stores (Neo4j)

  15. Key-Value Store

  16. Key-value store • Key–value (k, v) stores allow the application to store its data in a schema-less way • Keys k – can be ? • Values v – objects not interpreted by the system • v can be an arbitrarily complex structure with its own semantics or a simple word • Good for unstructured data • Data could be stored in a datatype of a programming language or an object • No meta data (except version#)

  17. Key-Value Stores • Simple data model • a.k.a. Map or dictionary • Put/request values per key • Length of keys limited, few limitations on value • High scalability over consistency • No complex ad-hoc querying and analytics • No joins, aggregate operations

  18. Dynamo • Amazon’s Dynamo – is a db plus distributed hash table • Highly distributed • Only store and retrieve data by primary key • Simple key/value interface, store values as BLOBs • Operations limited to k,v at a time • Get(key) returns list of objects and a context • Put(key, context, object) no return values • Context is metadata, e.g. version number • Can also delete

  19. Dynamo • Is that all? • Versioning • Efficient ways of storing based on hash of key • Replication

  20. DynamoDB • Precursor to Document Store • Based on Dynamo • Can create tables, define attributes, etc. • Have 2 APIs to query data • Query • Scan

  21. DynamoDB - Query • A Query operation • searches only primary key attribute values • Can Query indexes in the same way as tables • supports a subset of comparison operators on key attributes • returns all of the item’s data for the matching keys (all of each item's attributes) • up to 1 MB of data per query operation • Always returns results, but can return empty results • Query results are always sorted by the range key •

  22. DynamoDB - Scan • Scan Similar to Query except: • examines every item in the table • User specifies filters to apply to the results to refine the values returned after scan has finished • Supports a specific set of comparison operators

  23. Sample Query and Scan • • This seems rather complex … •

  24. Document Store

  25. Document Store • Notion of a document • Documents encapsulate and encode data in some standard formats or encodings • Encodings include: • JSON and XML • binary forms like BSON, PDF and Microsoft Office documents • Good for semi-structured data, but OK for unstructured, structured

  26. Document Store • More functionality than key-value • More appropriate for semi-structured data • Recognizes structure of objects stored • Objects are documents that may have attributes of various types • Objects grouped into collections • Simple query mechanisms to search collections for attribute values

  27. Document Store • Typically (e.g. MongoDB) • Collections correspond to tables in RDBS • Document corresponds to rows in RDBS • Fields correspond to attributes in RDBS • But not all documents in a collection have same fields • Documents are addressed in the database via a unique key • Allows beyond the simple key-document (or key–value) lookup • API or query language allows retrieval of documents based on their contents

  28. MongoDB Specifics

  29. MongoDB • huMONGOus • MongoDB – document-oriented organized around collections of documents • Each document has an ID (key-value pair) • Collections can be created at run-time • Documents’ structure not required to be the same, although it may be

  30. To issue a command in MongoDB • First must specify the Database to use use DatabaseName • Then start querying DatabaseName.CollectionName.Method();

  31. Create a collection • Create a collection (optional) • db.collection.createCollection() • Can specify the size, index, max# • If capped collection, fixed size and writes over • OR just use it in an insert and it will be created

  32. MongoDB • Can build incrementally without modifying schema (since no schema) • Each document automatically gets an _id • Example of hotel info – creating 3 documents: d1 = {name: "Metro Blu", address: "Chicago, IL", rating: 3.5} d2 = {name: "Experiential", rating: 4, type: “New Age”} d3 = {name: "Zazu Hotel", address: "San Francisco, CA", rating: 4.5}{name: "Motel 6", options: {smoking: "yes", pet: "yes"}});

  33. MongoDB • DB contains collection called ‘hotels’ with 4 documents • To list all hotels: • Did not have to declare or define the collection • Hotels each have a unique key • Not every hotel has the same type of information

  34. MongoDB • Queries DO NOT look like SQL • To query all hotels in CA (searches for regular expression CA in string) { rating: 4.5} ); { address : { $regex : "CA" } } );

  35. Data types • Mongo stores objects in BSON format • Binary encoding of JSON • Uses associative arrays • A field in Mongodb can be any BSON data type including: • Nested (embedded) documents • Arrays • Arrays of documents { name: {first: “Sue”, last: “Sky”}, age: 39, teaches: [“database”, “cloud”] degrees: [{school: “UIUC”, degree: “PhD”}, {school: “SIU”, degree: “MS”}, {school: “Northwestern”, degree: “BA”}] }

  36. MongoDB • Operations in queries are limited • must implement any additional operations in a programming language (JavaScript for MongoDB) • No Join - but can use $lookup • Can use mongo shell scripts • Many performance optimizations must be implemented by developer • MongoDB does have indexes • Single field indexes – at top level and in sub-documents • Text indexes – search of string content in document • Hashed indexes – hashes of values of indexed field • Geospatial indexes and queries

  37. Collection Methods • Collection methods • CRUD • insert(), find(), update(), remove() • Also • count(), aggregate(), etc.

  38. CRUD • Write – insert/update/remove • Create • db.createCollection(collection) //or can create on the fly • Insert • db.collection.insert({name: ‘Sue’, age: 39}) • Remove • db.collection.remove({} ) //removes all docs • db.collection.remove({status: “D”}) //some docs

  39. CRUD • Update • db.collection.update({age: {$gt: 21}}, // criteria {$set: {status: “A”}}, //action {multi: True} ) //updates multiple docs • Can change the value of a field, replace fields, etc. •

  40. FYI • Case sensitive to field names, collection names, e.g. Title will not match title

  41. CRUD • Read – a query returns a cursor that you can use in subsequent cursor methods • db.collection.find( ..)

  42. Find() Query db.collection.find(<criteria>, <projection>) db.collection.find{{select conditions}, {project columns}) Select conditions: • To match the value of a field use : db.collection.find({c1: 5}) • Everything for select ops must be inside of { } • For multiple “and” conditions can list: db.collection.find({c1:5, c2: “Sue”})

  43. Find() Query • Selection conditions • Can use other comparators, e.g. $gt, $lt, $regex, etc. db.collection.find({c1: {$gt: 5}}) • Can connect with $and or $or and place inside brackets [] db.collection.find({$and: [{c1: {$gt: 5}}, {c2: {$lt: 2}}] }) Same as db.collection.find({c1: {$gt: 5}, c2: {$lt: 2}})

  44. Find() to Query Projection: • If want to specify a subset of fields • 1 to include, 0 to not include (_id:1 is default) • Cannot mix 1s and 0s, except for _id db.collection.find({Name: “Sue”}, {Name:1, Address:1, _id:0}) • If you don’t have any select conditions, but want to specify a set of columns: db.collection.find({},{Name:1, Address:1, _id:0})

  45. Querying Fields • When you reference a field within an embedded document • Use dot notation • Must use quotes around the dotted name • “address.zipcode” • Quotes around a top-level field are optional • Use curly braces when includes an operation, e.g. {name: “Sue”}

  46. Cursor functions • The result of a query (find() ) is a cursor object • Pointer to the result set of a query • Iterable object (forward only) • Cursor function applies a function to the result of a query • E.g. limit(), etc. • For example, can execute a find(…) followed by one of these cursor functions db.collection.find().limit(10)

  47. Cursor Methods • cursor.count() • db.collection.find().count() • cursor.pretty() • cursor.sort() • cursor.toArray() • cursor.hasNext(), • Look at the documentation to see other methods

  48. Cursor Method Info • if the cursor returned from the a command such as db.collection.find() is not assigned to a variable using the var keyword, then the mongo shell automatically iterates the cursor up to 20 times • You have to indicate if you want it to iterate 20 more times, e.g. ‘it’

  49. Cursor iterate example • Cursor returned from the find() varmyCursor= db.users.find({type:2}) • Iterates 20 times with myCursor • Or can use next() to iterate over cursor • Can specify a while from command line in the mongo shell • Or can use forEach() • See next slide

  50. Cursors • To print using mongo shell script in the command line: • First set a variable equal to a cursor varc = db.testData.find() • Print the full result set by using a while loop to iterate over the cursorvariable c: while ( c.hasNext() ) printjson( )