Optimizer improved statistics collection

摘要

Described are techniques for performing compression and decompression of statistical data. This data may be used in connection with performing optimizations. A delta value for each statistic is determined representing a difference between a current value and a previous value. Delta values are stored in a statistics table in a compressed form using a monotonic compression scheme. Small tables are used to determine decompressed values estimating the observed values. Statistical information is stored and represented in a statistics table and an events table. Statistical information is selectively fetched and loaded into memory from a storage device. Indexing techniques are used to force physical continuity of the rows of the statistics table on a storage device in accordance with a specified retrieval order.