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CSE544 Introduction Monday, March 27, 2006 Staff • Instructor: Dan Suciu – CSE 662, [email protected] – Office hours: Wednesdays, 12pm-1pm • TA: Bhushan Mandhani – Office hours: TBA • Mailing list: [email protected] – http://mailman.cs.washington.edu/mailman/private/cse544 • Web page: (a lot of stuff already there) http://www.cs.washington.edu/544 Course Times • Mon, Wed, 10:30-12 • Final: – 8:30-10:20 a.m. Monday, Jun. 5, 2006 – In this room Goals of the Course • Using database systems • Foundations of data management. • Issues in building database systems. • Current research topics in databases. Format Basic structure: • Lectures on Wednesdays • Paper discussions on Mondays (reviews !) Content • Data modeling basics (3weeks): – SQL/XQuery with homeworks on Postgres/Galax – Logical foundations of databases • Transactions (2weeks): – concurrency control (locks, timestamps) – recovery (undo, redo, undo/redo) • Topics in query execution/optimization (3weeks) • Database security (1 week) • Databases + IR, Probabilistic databases (1 week) Textbooks Won’t follow any book, but you may want to consult them if you need more details to understand a topic • Database Management Systems, Ramakrishnan • The Complete Book, GarciaMolina, Ullman, Widom • Xquery from the Experts, Howard Katz, Ed. • Data on the Web, Abiteboul, Buneman, Suciu • Theory of database systems, Abiteboul, Hull, Vianu Grading • • • • • Homework: 20% Paper reviews: 20% Participation in the discussions: 10% Project: 30% Final: 20% Homework: 20% HW1: minor programming in SQL and Xquery HW2: problem sets, no programming theory, optimizations, query execution, transactions Project: 30% • Choose from a list of mini-research topics, or come up with your own • Open ended • Write short research paper (2-3 pages) • Conference-style presentation Project: 30% • Goals: apply database principles to a new problem – – – – Understand and model the problem Research and understand related work (1-2 papers) Propose some new approach (creativity will be evaluated) Implement some part • NOT intended to be a major software development • Amount of work may vary widely between groups Project: 30% Milestones: • Groups of 1-3 assembled by 4/5 • Proposals due by 4/10 • Short research papers (2-3pages) due by 5/30 • Presentations on 5/31 in class (MAY TAKE LONGER THAN 12pm) Paper Reviews: 20% • There will be reading assignments • Papers are discussed Mondays • You have to write the reviews by Sunday night Final: 20% • June 5, 8:30-10:30, same room • Challenging and fun Database What is a database ? Give examples of databases Database What is a database ? • A collection of files storing related data Give examples of databases • Accounts database; payroll database; UW’s students database; Amazon’s products database; airline reservation database Database Management System What is a DBMS ? Give examples of DBMS Database Management System What is a DBMS ? • A big C program written by someone else that allows us to manage efficiently a large database and allows it to persist over long periods of time Give examples of DBMS • DB2 (IBM), SQL Server (MS), Oracle, Sybase • MySQL, Postgres, … Market Shares From 2004 www.computerworld.com • IMB: 35% market with $2.5BN in sales • Oracle: 33% market with $2.3BN in sales • Microsoft: 19% market with $1.3BN in sales An Example The Internet Movie Database http://www.imdb.com • Entities: Actors (800k), Movies (400k), Directors, … • Relationships: who played where, who directed what, … Want to store and process locally; what functions do we need ? Functionality 1. 2. 3. 4. 5. 6. Create/store large datasets Search/query/update Change the structure Concurrent access to many user Recover from crashes Security (not here, but in other apps) Possible Organizations • Files • Spreadsheets • DBMS 1. Create/store Large Datasets • Files • Spreadsheets • DBMS Yes, but… Not really… Yes 2. Search/Query/Update • Simple query: – In what year was ‘Rain man’ produced ? • Multi-table query: – Find all movies by ‘Coppola’ • Complex query: – For each actor, count her/his movies • Updating – Insert a new movie; add an actor to a movie; etc 2. Search/Query/Update • Files • Spreadsheets Simple queries Multi-table queries (maybe) • DBMS All Updates: generally OK 3. Change the Structure Add Address to each Actor • Files • Spreadsheets • DBMS Very hard Yes Yes 4. Concurrent Access Multiple users access/update the data concurrently • What can go wrong ? • How do we protect against that in OS ? • This is insufficient in databases; why ? 4. Concurrent Access Multiple users access/update the data concurrently • What can go wrong ? – Lost update; resulting in inconsistent data • How do we protect against that in OS ? – Locks 4. Concurrent Access Transfer $100 from account A to B: X = Read(Accounts, A); X.amount = X.amount - 100; Write(Accounts, A, X); Y = Read(Accounts, B); Y.amount = Y.amount + 100; Write(Accounts, B, Y); Find total amount in A and B: X = Read(Accounts, A); Y = Read(Accounts, B); S = X.amount + Y.amount return S What can go wrong ? Do locks help ? 5. Recover from crashes X = Read(Accounts, A); X.amount = X.amount - 100; Write(Accounts, A, X); Y = Read(Accounts, B); Y.amount = Y.amount + 100; Write(Accounts, B, Y); What is the problem ? CRASH ! Enters a DMBS “Two tier system” or “client-server” connection (ODBC, JDBC) Data files Database server (someone else’s C program) Applications DBMS = Collection of Tables Directors: Movie_Directors: id fName lName id mid 15901 Francis Ford Coppola 15901 130128 ... ... Movies: mid Title Year 130128 The Godfather 1972 ... Still implemented as files, but behind the scenes can be quite complex “data independence” 1. Create/store Large Datasets Use SQL to create and populate tables: CREATE TABLE Actors ( Name CHAR(30) DateOfBirth CHAR(20) ) ... INSERT INTO Actors VALUES(‘Tom Hanks’, . . .) Size and physical organization is handled by DBMS We focus on modeling the database Will study data modeling in this course 2. Searching/Querying/Updating • Find all movies by ‘Coppola’ SELECT title FROM Movies, Directors, Movie_Directors WHERE Directors.lname = ‘Coppola’ and Movies.mid = Movie_Directors.mid and Movie_Directors.id = Directors.id • What behind scenedetails ? Wehappens will study SQL the in gory in this course We will discuss the query optimizer in class. 3. Changing the Structure Add Address to each Actor ALTER TABLE Actor ADD address CHAR(50) DEFAULT ‘unknown’ Lots of cleverness goes on behind the scenes 3&4 Concurrency&Recovery: Transactions • A transaction = sequence of statements that either all succeed, or all fail • E.g. Transfer $100 BEGIN TRANSACTION; UPDATE Accounts SET amount = amount - 100 WHERE number = 4662 UPDATE Accounts SET amount = amount + 100 WHERE number = 7199 COMMIT Transactions • Transactions have the ACID properties: A = atomicity C = consistency I = isolation D = durability 4. Concurrent Access • Serializable execution of transactions – The I (=isolation) in ACID We study three techniques in this course Locks Timestamps Validation 5. Recovery from crashes • Every transaction either executes completely, or doesn’t execute at all – The A (=atomicity) in ACID We study three types of log files in this course Undo log file Redo log file Undo/Redo log file