Memoization in Cost-based Optimizers
DZone
JUNE 13, 2021
Query optimization is an expensive process that needs to explore multiple alternative ways to execute the query. The query optimization problem is NP-hard , and the number of possible plans grows exponentially with the query’s complexity. For example, a typical TPC-H query may have up to several thousand possible join orders, 2–3 algorithms per join, a couple of access methods per table, some filter/aggregate pushdown alternatives, etc.
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