ANALYZE INDEX clause

最新推荐文章于 2025-12-15 12:08:33 发布

转载最新推荐文章于 2025-12-15 12:08:33 发布 · 88 阅读

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#人工智能

本文详细介绍了Oracle数据库中索引的统计信息，包括索引深度、叶子块数量、不同索引值的数量等，并解释了如何使用ANALYZE INDEX命令进行分析。

Oracle Database collects the following statistics for an index. Statistics
marked with an asterisk are always computed exactly. For conventional indexes,
when you compute or estimate statistics, the statistics appear in the data
dictionary views USER_INDEXES,ALL_INDEXES, and DBA_INDEXES in the columns shown
in parentheses.
■ * Depth of the index from its root block to its leaf blocks (BLEVEL)
■ Number of leaf blocks (LEAF_BLOCKS)
■ Number of distinct index values (DISTINCT_KEYS)
■ Average number of leaf blocks for each index value (AVG_LEAF_BLOCKS_PER_KEY)
■ Average number of data blocks for each index value (for an index on a table)
(AVG_DATA_BLOCKS_PER_KEY)
■ Clustering factor (how well ordered the rows are about the indexed values)
(CLUSTERING_FACTOR)

使用ANALYZE INDEX 分析索引的root块至叶子块的深度，叶子块数目， distinct索引值等信息，将分析数据保存在*INDEXES等视图的BLEVEL,LEAF_BLOCKS等字段

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