本文介绍了数据库中索引和散列的基本概念，包括两种基本类型的索引：有序索引和散列索引。详细讨论了评价指标如访问类型、访问时间等，并深入解释了一级索引、二级索引及B+树索引文件的概念。
Indexing and Hashing
basic concepts
two basic kind of indices: ordered indices and hash indices
evaluating factors:
Access types
Access time
Insertion time
Deletion time
Space overhead
ordered indices
primary index: an index whose search key also defines the sequential order of the file
densw and sparse indices
multilevel index: smaller!
secondary indices: an index whose search key specifies an order different from the sequential order of the file
must be dense, The pointer in a secondary index do not point directly to the file. Instead, each point to a bucket that contains pointers to the file.
B+ Tree index files
basic concepts
two basic kind of indices: ordered indices and hash indices
evaluating factors:
Access types
Access time
Insertion time
Deletion time
Space overhead
ordered indices
primary index: an index whose search key also defines the sequential order of the file
densw and sparse indices
multilevel index: smaller!
secondary indices: an index whose search key specifies an order different from the sequential order of the file
must be dense, The pointer in a secondary index do not point directly to the file. Instead, each point to a bucket that contains pointers to the file.
B+ Tree index files
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