文档介绍:IndexTuningShasha,esstodataSetofRecordsindexConditiononattributevalueMatchingrecords(searchkey)Shasha,anizationofdataondiskIndexOverheadDataDistributionCoveringShasha,2001TypesofQueriesPointQuerySELECTbalanceountsWHEREnumber=1023;MultipointQuerySELECTbalanceountsWHEREbranchnum=100;RangeQuerySELECTnumberountsWHEREbalance>10000;PrefixMatchQuerySELECT*FROMemployeesWHEREname=‘Jensen’ andfirstname=‘Carl’ andage<30;Shasha,2001TypesofQueriesExtremalQuerySELECT*ountsWHEREbalance=max(ounts)OrderingQuerySELECT*ountsORDERBYbalance;GroupingQuerySELECTbranchnum,avg(balance)ountsGROUPBYbranchnum;JoinQueryounts,branchWHERE= >10000;Shasha,2001SearchKeysA(search)(branchnum,balance);TypesofkeysSequential:thevalueofthekeyismonotonicwiththeinsertionorder(.,counterortimestamp)Nonsequential:thevalueofthekeyisunrelatedtotheinsertionorder(.,socialsecuritynumber)Shasha,,therootofthistreewillalwaysbeinmainmemory,-out(maximumnumberofchildrenofaninternalnode),2001B+-TreeAB+-Treeisabalancedtreewhoseleavescontainasequenceofkey-,2001B+-reelockingTreerootinmainmemoryShasha,2001