PostgreSQL的磁盘空间占用问题

　　ThefirstcolumnofthechartistheGUCsettinginthepostgresql.conffile.　

　　Thesecondisthemaximumrangeofthevariable;notethatthemaximumrangeisoftenmuchlargerthanthepracticalrange.Forexample,random_page_costwillacceptanynumberbetween0andseveralbillion,butallpracticalnumbersarebetween1and5.　

　　ThethirdcolumncontainsanenumerationofRAMordiskspaceusedbyeachunitoftheparameter.　

　　ThefourthcolumnindicateswhetherornotthevariablemaybeSETfromthePSQLterminalduringaninteractivesetting.Mostsettingsmarkedas"no"mayonlybechangedbyrestartingPostgreSQL.　

　　ThefifthcolumnquotestheofficialdocumentationavailablefromthePostgreSQLwebsite.　

　　Thelastcolumnisournotesonthesetting,howtosetit,resourcesituses,etc.You'llnoticesomeblankspaces,andshouldbewarnedaswellthatthereisstillstrongdisagreementonthevalueofmanysettings.　

　　UsersofPostgreSQL7.3andearlierwillnoticethattheorderoftheparametersinthisguidedonotmatchtheorderoftheparametersinyourpostgresql.conffile.Thisisbecausethisdocumentwasgeneratedaspartofanefforttore-organizetheconfparametersanddocumentation;startingwith7.4,thisdocument,theofficialdocumentation,andthepostgresql.conffileareallinthesamelogicalorder.　

　　Asnotedintheworksheet,itcoversPostgreSQLversions7.3and7.4.Ifyouareusinganearlierversion,youwillnothaveaccesstoallofthesesettings,anddefaultsandeffectsofsomesettingswillbedifferent.