{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Session10 - Chapter 12 Indexing and Hashing Basic Concepts...

Info icon This preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Database Management Systems 3ed, R. Ramakrishnan and J. Gehrke 1 Chapter 12: Indexing and Hashing Chapter 12: Indexing and Hashing xrhombus Basic Concepts xrhombus Ordered Indices xrhombus B+-Tree Index Files xrhombus B-Tree Index Files xrhombus Static Hashing xrhombus Dynamic Hashing xrhombus Comparison of Ordered Indexing and Hashing xrhombus Index Definition in SQL xrhombus Multiple-Key Access
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Database Management Systems 3ed, R. Ramakrishnan and J. Gehrke 2 Basic Concepts Basic Concepts xrhombus Indexing mechanisms used to speed up access to desired data. square4 E.g., author catalog in library xrhombus Search Key - attribute or set of attributes used to look up records in a file. xrhombus An index file consists of records (called index entries ) of the form xrhombus Index files are typically much smaller than the original file xrhombus Two basic kinds of indices : square4 Ordered indices: search keys are stored in sorted order square4 Hash indices: search keys are distributed uniformly across “buckets” using a “hash function”. search-key pointer
Image of page 2
Database Management Systems 3ed, R. Ramakrishnan and J. Gehrke 3 Index Evaluation Metrics Index Evaluation Metrics xrhombus Access types supported efficiently. E.g., square4 records with a specified value in the attribute square4 or records with an attribute value falling in a specified range of values. xrhombus Access time xrhombus Insertion time xrhombus Deletion time xrhombus Space overhead Indexing techniques evaluated on basis of:
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Database Management Systems 3ed, R. Ramakrishnan and J. Gehrke 4 Ordered Indices Ordered Indices xrhombus In an ordered index , index entries are stored sorted on the search key value. E.g., author catalog in library. xrhombus Primary index : in a sequentially ordered file, the index whose search key specifies the sequential order of the file. square4 Also called clustering index /* Not! */ square4 The search key of a primary index is usually but not necessarily the primary key. xrhombus Secondary index : an index whose search key specifies an order different from the sequential order of the file. Also called non-clustering index . /* Wrong Again! */ xrhombus Index-sequential file : ordered sequential file with a primary index.
Image of page 4
Database Management Systems 3ed, R. Ramakrishnan and J. Gehrke 5 Dense Index Files Dense Index Files xrhombus Dense index — Index record appears for every search-key value in the file.
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Database Management Systems 3ed, R. Ramakrishnan and J. Gehrke 6 Sparse Index Files Sparse Index Files xrhombus Sparse Index : contains index records for only some search-key values.
Image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}