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Query Optimization - Coggle Diagram
Query Optimization
Transformation of Relational
Expressions
Can improve the efficiency of a practice's evaluation.
Can simplify the logic of a query and make it easier to understand and debug.
Using the algebraic and logical properties of relational algebra, expressions can be simplified and reorganized to make them more intuitive.
Common transformations
combination of operations
Commutativity of operations
Associativity of operations
Elimination of redundant operations
Optimization of queries in database management systems
Equivalence, Join Ordering
Estimating Statistics of Expression
Result
The cost of an operation depends on the size and statistics of its inputs
Database-system catalogs store statistics about relations
Statistics can be used to estimate the results of various relational operations.
Choice of Evaluation Plans
Distributed databases allow for data to be stored and processed across multiple computers in a network
Scalability, fault tolerance, and improved performance.
Transactions can be executed concurrently across multiple nodes
Must ensure consistency
Distribution of data
Replication, fragmentation, or a combination of both