Consultor Eletrônico

Version 7 - What is the benefit of index compression

This knowledge base document describes the added benefit of index
compressed introduced in Version 7.

What is an Index?

An index is a field or combination of fields from one table that
Progress uses as the basis for searching, sorting, or otherwise
processing the records of that table. Records are found by referencing
a key associated with a particular recid by the use of the Index
Anchor table. In Progress Version 6, the entire key was stored in
the index. Key Compression has been implemented as a new feature in
Progress Version 7.

What is Key Compression?

Key Compression is the elimination of redundant information in the
stored keys. Compression saves space and allows for faster compression
This is an internal feature implemented with Progress Version 7.

For example:

VERSION 6 VERSION 7
City Recid City Recid

Bolonia 3331 Bolonia 3331
Bolton 5554 ton 5554
Bolton 9001 9001
Bolton 9022 22
Bonn 8001 nn 8001
Boston 1111 ston 1111
Boston 1118 8
Boston 7001 7001
Cardiff 3333 Cardiff 3333


Converting a Version 6 database to Version 7 using CONV67

With Version 7 came a new utility to automatically convert a Version
6.3 database to a Version 7 database. You may notice after the
conversion that there will may be less index blocks utilized for all
of the indexes. You can see this my running the Index Analyis utility

before and after the database conversion. The amount of index blocks
freed up to be put on the free chain depends on how fragmented the
indexes were before the conversion.


99 index block(s) found in the database.
48.5% of the index block space is used.


How is Index Locking affected?

To prevent data corruption, index blocks must be locked during current
usage. In Version 7, only those blocks that need to be locked are
locked. In Version 6, the entire B-tree was locked when in use.

Progress Software Technical Support Note # 16809