Query Cache Architecture

The query cache consists of cache storage space, cache metadata, and cache detection in query

compilation.

The process of accessing the cache metadata is very fast. If the metadata shows a cache hit, the

bulk of the query processing is eliminated, and the results are immediately returned to the user. The process of adding the new results to the cache is independent of the results being returned to the user; the only effect on the running query is the resources consumed in the process of writing the cached results.

When a user request a query, the Presentation Server translate the query into Logical Query and send it to the BI Server. The BI Server searches the Cache Metadata for a matched Logical Query. If the matched Logical query is found (called as Cache Hit), then the results are retrieved from Query Cache by BI Server and sent it to Presentation Server. If the matched query is not found, then the BI server will generate the Physical Query and send it to the underlying Database. The Database processes the physical query and return the result to the BI Server, the Bi Server will send back the result set to Presentation Server and at the same time store the result set in the Query Cache.