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1、TheunderlyingtechnologyofQlikViewQlikTech*finallydecidedbothtobecomeaclientand,surelynotcoincidentally,togivememoretechnicaldetailaboutQlikViewthanithadwhenlastwetalkedacoupleofyearsago.Indeed,IgottospendacoupleofhoursonthephonenotjustwithAnthonyDeighton,butalsowithQlikTe
2、ch’sHakanWolge,whowrote70-80%ofthecodeinQlikView1.0,andremainsineffectQlikTech’schiefarchitecttothisday.*Or,asitnowappearstobecalled,QlikTechnologies.Let’sstartwithsomequickreminders:•QlikTechmakesQlikView,awidelypopularbusinessintelligence(BI)toolsuite.•QlikViewisdisting
3、uishedbytheflexibilityofnavigationthroughitsuserinterface.•Tosupportthisflexibility,QlikViewpreloadsalldatayoumightwanttoqueryintomemory.Let’salsodisposeofoneconfusionrightupfront,namelyQlikTech’suseofthewordassociative:•NotwithstandingQlikTech’srepeateduseofphraseslike“Q
4、likView’sunique,patentedin-memoryassociativetechnology,”thereisnothing“associative”aboutQlikView’sdatastructures.•Rather,“associative”isatermthatcanreasonablybeusedtodescribethefunctionalityofQlikView’suserinterface.Inparticular,QlikViewcan“associate”overfieldsthathavethe
5、samename,inthatitmakesiteasyforuserstojoinacrossthem.Withthatoutoftheway,let’sturntosomehighlightsofQlikView’sunderlyingtechnology.Forthemostpart,QlikView’sin-memorydatastructuresarequitesimple.Inparticular:oQlikViewdataisstoredinastraightforwardtabularformat.oQlikViewdat
6、aiscompressedviawhatQlikTechcallsa“symboltable,”butIgenerallycall“dictionary”or“token”compression.oQlikViewtypicallygetsatitsdataviascans.Thereisverylittleinthewayofprecomputedaggregates,indexes,andthelike.Ofcourse,iftheselectionhappenstobeinlinewiththeorderinwhichthereco
7、rdsaresorted,youcangetgreatselectivityinascan.oOneadvantageofdoingtokencompressionisthatallthefieldsinacolumnwindupbeingthesamelength.Thus,QlikViewholdsitsdatainnicearrays,sotheaddressesofindividualrowscanoftenbeeasilycalculated.TogetitsUIflexibility,QlikViewimplicitlyass
8、umesastar/snowflakeschema.Thatis,thereshouldbenomoreandnolessthanonepossiblejoinpathbetweenanypa
