Common Query Rewriting Techniques
- Predicate Pushdown: with this approach, you crop unnecessary predicates from the inner query blocks to the external query block, which eventually minimizes the amount of data retrieved and processed from involved resources. Thus, the senescence of the predicate pushdown layer remains the main thing that decreases the whole query processing time by doing actions such as nested queries or joins as soon as it is possible.
- Join Decomposition: This type of joint operation, however, can cause the system to work beyond its capacity if proper attention is not paid and particular issues are resolved. The following breakdown in the splitting of sheer huge join operations into simpler and shorter componentwise operations makes the workload less and speeds up its execution process.
- Subquery Unnesting: Subqueries, although they have the advantage of concise technical simplicity, become troublesome because of their nested nature. The subquery unnesting converts subqueries to joins or other structures provided by the query optimizer’s choice of mapping mechanisms that result in faster and more efficient execution plans.
- View Materialization: Database systems can be materialized by performing precomputing and storing the results, which are frequently asked, queries. Therefore, it becomes possible to steer clear of the cumbersomeness of these calculations and their subsequent performance losses by including them in the view definition.
- Query Expansion: Such an area can be increased by additionally including additional search terms or sequencing specifications to a query to support its plan. A stronger query optimizer can reveal its abilities after being provided with that information, as it will be able to take the appropriate decisions regarding index usage, join orders, and access paths. It, so, provides the base.
What is Query Rewriting Techniques in DBMS
In the world of DBMS, efficiency and optimization define everything; as a result, it is the most important. The art of optimization is used to enhance database queries. It is Query rewriting. The process of query rewriting pertains to the conversion of the given form query into an equivalent form that enables the search to be executed faster with the use of many optimization strategies.