Browse Prior Art Database

Efficient Collection of Index Statistics

IP.com Disclosure Number: IPCOM000121017D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 46K

Publishing Venue

IBM

Related People

Comeau, A: AUTHOR [+2]

Abstract

Disclosed is a method to collect statistics describing the properties of an index with minimal cost. This method has been implemented in the SQL/DS* relational database management system (RDBMS).

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Efficient Collection of Index Statistics

      Disclosed is a method to collect statistics describing
the properties of an index with minimal cost.  This method has been
implemented in the SQL/DS* relational database management system
(RDBMS).

      RDBMs which have access path optimization logic typically use
summary statistics to model the indexes which exist in the database.
The optimizer uses these statistics in determining the most efficient
data access path.  The efficiency of the access path is limited by
the accuracy and timeliness of the statistics.

      Index statistics are usually generated by scanning the
appropriate index and accumulating the necessary information.  This
information is then used to derive the statistics, and they are
stored for later reference by the optimizer.  SQL/DS stores such
statistics in its catalog tables.

      Generating index statistics requires that each index entry be
visited, in sequence, and that the logical and physical structure of
the index tree be inferred.  Building an index involves handling each
index entry in sequence, as well as defining the logical and physical
structure of the index tree.  The new statistics generation method
combines the building of the index with the collection of the
descriptive information.  This removes the need for a costly scan of
the index tree.  All required information is available as index
entries are encountered in sequence, and the index tree structure is
known...