SimpleDB OverviewCSE444– Section1

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Today…

• DemoGit/EclipseSetup• GothroughanoverviewofSimpleDB

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LocalRepository/home/jortiz16

GitLab IndividualRepositorygit@.../simple-db-jortiz16

GitLab CourseRepositorygit@.../simple-db

Forked(byus)

Origin RemoteCloned(byyou)

Upstream RemoteAdded(byyou)

git pushgit pull

git pullupstreammaster

Git

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WhatyoushouldNOTdo:

•Modifygivenclasses• Removing,renaming,relocatingtootherpackages

•Modifygivenmethods• Changingparametersorreturntypes

• Usethird-partylibraries• Excepttheonesunderlib/directory• YoucandoeverythingusingregularJavalibraries

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WhatyouCANdo:

• Addnewclasses/interfaces/methods/packages•Watchoutfornameconflictswithfuturelabs!• Saferchoice:usenewpackages(best)orinnerclasses(meh)

• Re-implementprovidedmethods• Justdon’tdestroycorrectnessorspecification!

• Findbugs!

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• Systemtestcases• Undertest/systemtest•We’llgradeusingadditionaltests

•Writeup• Explainwhydoyouimplementinthatway

•We’llreadyourcode• Readinghorriblecodeishorrible,sospendsometimepolishing• Passingallthetestcasesmaynotnecessarymeanyou’llgetahighscore

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WhatyouCANdo(continued):

SettingupSimpleDBAnyquestionsorconcerns?

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OverviewofSimpleDB

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Database

•Asingledatabase• Oneschema• Listoftables

•Referencestomajorcomponents• GlobalinstanceofCatalog• GlobalinstanceofBufferPool

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Catalog

•Storesmetadataabouttablesinthedatabase• voidaddTable(DbFile d,TupleDesc d)• DbFile getTable(int tableid)• TupleDesc getTupleDesc(int tableid)• …

•NOTpersistedtodisk• CataloginfoisreloadedeverytimeSimpleDB startsup

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BufferPool

•TheONLYbridgebetweendata-processingoperatorsandactualdatafiles• Strictinterfaceforphysicalindependence!

•Datafilesareneveraccesseddirectly• Laterlabs:• Lockingfortransactions• Flushingpagesforrecovery

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DataTypes

•Integer• Type.INT_TYPE• 4bytewidth

•Fixed-lengthStrings• Type.STRING_TYPE• 128byteslong(Type.STRING_LEN)• Donotchangethisconstant!

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DbIterator

•Ancestorclassforalloperators• Join,Project,SeqScan,etc…

•Eachoperatorhasmethods:• open(),close(),getTupleDesc(),hasNext(),next(),rewind()

• Iteratormodel:chainiteratorstogether

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HeapFile

•Mainclassthatorganizesthephysicalstorageoftables•CollectionofHeapPages ondisk• OneHeapFile foreachtable• Fixed-sizepagesmeansefficientlookupofpages

HeapPage #1

HeapPage #2

HeapPage #3

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HeapPage

•A chunkofdatathatcanresideintheBufferPool•Format:Header+Tuples• #of1bitsinBitmap=#ofactivetuplesonpage

•Fixedsize:BufferPool.PAGE_SIZE Header Bitmap

Tuple #1

Tuple #2

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Questions?

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