Câu hỏi phỏng vấn [Global] Caching
Câu hỏi

What is Resultset Caching?

Câu trả lời

Resultset caching is a technique used to improve the performance of database queries by storing the results of a query so that subsequent requests for the same data can be served more quickly from the cache rather than re-executing the query against the database. This approach reduces the load on the database and speeds up data retrieval.

Key Concepts of Resultset Caching

  1. Definition and Purpose:

    • Resultset caching involves storing the results of a database query in a cache. When the same query is executed again, the results are retrieved from the cache instead of querying the database again, which reduces latency and improves performance[1][3][6].
  2. Implementation:

    • Oracle WebCenter Sites: Uses the wcs_properties.json file to set global and table-specific caching properties. The resultsets can be cached using the inCache framework or hash tables, and administrators can switch between these frameworks as needed[1].
    • AWS: Implements resultset caching by serializing the ResultSet object and storing it in a cache like Redis. This approach abstracts the data retrieval logic, making it transparent whether the data comes from the database or the cache[2][4].
    • Azure Synapse Analytics: Caches query results in the user database for repetitive use. This feature is beneficial for reducing compute resource usage and improving query performance. It is particularly useful for scenarios involving repetitive queries, such as those used in Power BI[3][6][9].
  3. Criteria and Limitations:

    • For a query to be cached, certain criteria must be met, such as no changes in the underlying data or schema, and the query must not use non-deterministic functions like GetDate()[3][6].
    • Cached results are typically invalidated when the underlying data changes, ensuring data consistency[10].
  4. Benefits:

    • Performance Improvement: By serving repeated queries from the cache, the system reduces the time and resources needed to fetch data from the database[3][6].
    • Resource Optimization: Cached queries do not consume additional database resources, which can be particularly beneficial in environments with limited compute resources[6][9].
  5. Use Cases:

    • Resultset caching is ideal for read-heavy applications where the same data is queried frequently, such as reporting tools and dashboards[9].
    • It is also useful in scenarios where data does not change frequently, allowing cached results to remain valid for longer periods[3][6].

Example Implementations

  • Oracle WebCenter Sites: Administrators can configure resultset caching by setting pro...
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