文档介绍：IndexTuningShasha,esstodataSetof RecordsindexCondition on attribute valueMatching records(searchkey)Shasha,anizationofdataondiskIndexOverheadDataDistributionCoveringShasha,2001TypesofQueriesPointQuery SELECTbalance ounts WHEREnumber=1023; MultipointQuery SELECTbalance ounts WHEREbranchnum=100;RangeQuery SELECTnumber ounts WHEREbalance>10000; PrefixMatchQuery SELECT* FROMemployees WHEREname=‘Jensen’ andfirstname=‘Carl’ andage<30;Shasha,2001TypesofQueriesExtremalQuery SELECT* ounts WHEREbalance= max(ounts)OrderingQuery SELECT* ounts ORDERBYbalance;GroupingQuery SELECTbranchnum,avg(balance) ounts GROUPBYbranchnum; JoinQuery ounts,branch WHERE = >10000;Shasha,2001SearchKeysA(search)(branchnum,balance);TypesofkeysSequential:thevalueofthekeyismonotonicwiththeinsertionorder(.,counterortimestamp)Nonsequential:thevalueofthekeyisunrelatedtotheinsertionorder(.,socialsecuritynumber)Shasha,,therootofthistreewillalwaysbeinmainmemory,-out(maximumnumberofchildrenofaninternalnode),2001B+-TreeAB+-Treeisabalancedtreewhoseleavescontainasequenceofkey-,2001B+-reelockingTreerootinmainmemoryShasha,2001