Briefly describe what the query evaluation engine performs inside a DB.docx
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The query evaluation engine within a DBMS is responsible for executing low-level instructions generated by the DML compiler following a query submission. It processes the execution plan, which is optimized by the query optimizer for efficiency, by transforming logical operators into physical operations while considering available resources. Key physical operations performed include sorting, hashing, and disk access.
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Briefly describe what the query evaluation engine performs inside a DB.docx
- 1. Briefly describe what the query evaluation engine performs inside a DBMS. Solution Generally we write queries to retrieve data from database.What we know is just simply submit the query.Actually,so many people don't know after submitting query What happend really in between submission of query and retrieving data is: query handeld to query processor .That query processor having different components to process that query one of the components of query processor is :query evaluation engine :1)it executes the low-level instructions that are generated by DML compiler.DML compiler generate the execution plan with that low-level instructions from the query. 2)query evaluation engine takes input from query optimizer and gives out physical operations. query optimizer produces best execution plan out of many plans by considering some cost like no of operations,cpu time etc.What actually execution plan consists is logical operators. These logical operators are taken by query evaluation engine and generate physical operations. While doing physical operation evaluation engine closely takes into the available resources like memory. physial operations like sorting,hashing,disk access etc.