Query optimization is a computationally intensive process, especially for the complex queries that are typical in current data warehousing and mining applications. The inherent overheads of query optimization are compounded by the fact that a new query is typically optimized afresh, providing no opportunity to amortize these overheads over prior optimizations. While current commercial query optimizers do provide facilities for reusing executionplans generated for earlier queries (e.g. "stored outlines" in Oracle 9i), the query matching is extremely restrictive-only if the incoming query has a close textual resemblance with one of the stored queries is the associated plan re-used to execute the new query.
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