galy Postgres查询处理简介

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1、QueryProcessing查询处理李元佳2013Postgres全国大会杭州目录SQLStandardQueryProcessingParserAnalysisRewritePlan/OptimizerExecutorSQLasQueryLanguageHigh-leveldeclarative,English-basedlanguagedeclarativelanguage:whatnothowwell-founded/simplesemanticsbasedonrelationalalg

2、ebrasmallsetofwell-understoodoperators,sooptimizerknows:howoperatorscanbeinterchanged/transformedwhatequivalentimplementationsareforeachopConsistentfordifferentfunctionalitiesdatadefinition:e.g.,tablecreation,viewdefinitiondatamanipulation:e.g.,queries,u

3、pdatesUniformfordifferentusagescenariosembeddingfromdifferenthostlanguages(cannedqueries)adhocuserqueriesfromcommandlinesUnexpectedbenefit:StandardizedDBinterface(mid80’s)3HistoryofSQL1970–E.Codddevelopsrelationaldatabaseconcept1974-1979–SystemRwithSeque

4、l(laterSQL)createdatIBMResearchLab1979–OraclemarketsfirstrelationalDBwithSQL1986–ANSISQLstandardreleased1989,1992,1999,2003,2011MajorANSIstandardupdatesCurrent–SQLissupportedbymostmajordatabasevendors4PurposeofSQLStandardSpecifysyntax/semanticsfordatadefi

5、nitionandmanipulationDefinedatastructuresEnableportabilitySpecifyminimal(level1)andcomplete(level2)standardsAllowforlatergrowth/enhancementtostandard5BenefitsofaStandardizedRelationalLanguageReducedtrainingcostsProductivityApplicationportabilityApplica

6、tionlongevityReduceddependenceonasinglevendorCross-systemcommunication6SQLStandard2011Part1:Framework(SQL/Framework)Part2:Foundation(SQL/Foundation)Part3:Call-LevelInterface(SQL/CLI)Part4:PersistentStoredModules(SQL/PSM)Part9:ManagementofExternalData(SQ

7、L/MED)Part10:ObjectLanguageBindings(SQL/OLB)Part11:InformationandDefinitionSchemas(SQL/Schemata)Part13:SQLRoutinesandTypesUsingtheJava™ProgrammingLanguage(SQL/JRT)Part14:XML-RelatedSpecifications(SQL/XML)SQLCatalogAsetofschemasthatconstitutethedescriptio

8、nofadatabaseSchemaThestructurethatcontainsdescriptionsofobjectscreatedbyauser(basetables,views,constraints)DataDefinitionLanguage(DDL)Commandsthatdefineadatabase,includingcreat