Arama motorları için verimli önbellekleme mekanızmaları

The performance of a search engine depends on its crawler, indexer and processor components. The query latency, accuracy and recency of the results play crucial role in determining the performance. High performance can be provided with powerful hardware, but keeping the operational costs restrained is mandatory for commercial durability. This thesis focuses on techniques to boost the performance of search engines by means of reducing the number of queries issued to the backend and the cost to process a query stream. This can be accomplished by taking advantage of the temporal locality of the queries. Caching the result for a recently issued query removes the need to reprocess this query when it is issued again. Therefore, deploying query result cache decreases the load on the resources of the search engine which increases the processing power. The main objective of this thesis is to improve search engine performance by enhancing productivity of result cache. This is done by endeavoring to maximize the cache hit rate and minimizing the processing cost by using the per query statistics such as frequency, timestamp and cost. While providing high hit rates and low processing costs improves performance, the freshness of the queries has to be considered as well for user satisfaction. Therefore, a variety of techniques are examined in this thesis to bound the staleness of cache results without blasting the backend with refresh queries. The o ered techniques are demonstrated to be effcient by using real query log data from a commercial search engine.